**2008 Hurricane Field Program Plan**

Hurricane Research Division

**National Oceanographic and Atmospheric Administration**

**Atlantic Oceanographic and Meteorological Laboratory**

**4301 Rickenbacker Causeway**

**Miami, FL 33149**

Prepared by:

John Gamache, Sim Aberson, Jason Dunion, Joe Cione, Robert Black, Robert
Rogers, Peter Dodge, John Kaplan, Peter Black, James Carswell, Eric
Uhlhorn, Matthew Eastin, Gary Barnes, and Rick Lumpkin

![](media/image2.png){width="2.472916666666667in"
height="0.4909722222222222in"} 30 June 2008

Frank D Marks, Jr Date

Director, Hurricane Research Division

> Distribution of the NOAA/HRD Hurricane Field Program Plan is
> restricted to personnel directly involved in the hurricane field
> program or to those persons who are on a need-to-know basis. This
> plan, in whole or in part, is not to be abstracted, cited or
> reproduced in the open literature.
>
> Mention of a commercial establishment, company or product does not
> constitute any endorsement by the NOAA/Office of Oceanic and
> Atmospheric Research or the U.S. Government. Use, for publicity of
> advertisement, of information from this publication concerning
> proprietary products or their testing is not authorized.
>
> ©2008, U.S. Department of Commerce, NOAA/AOML/Hurricane Research
> Division
>
> **Cover**: To be changed

Table of Contents

**INTRODUCTION**

**Operations**

1.  Locations..........................................................................................................
    5

2.  Field Program
    Duration.........................................................................................
    5

3.  Research Mission
    Operations..................................................................................
    5

4.  Task Force
    Configuration....................................................................................\...
    5

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5.  Field
    Operations..................................................................................................
    5

> 5.1 Scientific Leadership
> Responsibilities..............................................................
> 5
>
> 5.2 Aircraft Scientific
> Crews.............................................................................
> 5
>
> 5.3 Principal Duties of the Scientific
> Personnel....................................................... 5
>
> 5.4 HRD
> Communications................................................................................
> 5
>
> 6\. Data
> Management.............................................................................................\...
> 6

7.  Operational
    Constraints.........................................................................................
    6

8.  Calibration of Aircraft
    Systems................................................................................
    6

**HRD RESEARCH EXPERIMENTS**

1.  Three-Dimensional Doppler Winds
    Experiment............................................................
    7

2.  Tropical Cyclone Landfall and Inland Decay
    Experiment................................................. 20

3.  Tropical Cyclone Unmanned Aerial System (UAS)
    Inflow/Eyewall/Eye/Experiment................ 38

    12 Tropical Cyclogenesis Experiment
    (GenEx)................................................................
    41

4.  Nadir Off-set SFMR
    Experiment...........................................................................\...
    49

5.  Tropical Cyclone/AEW Arc Cloud
    Experiment..........................................................\...
    50

6.  Saharan Air Layer Experiment
    (SALEX)........................................\.............................
    53

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1.  

2.  Sea-Salt Aerosol and Cloud Base Number Concentration
    Experiment................................... 61

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7.  Eyewall Microphysics
    Experiment............................................................................
    65

8.  TC-Ocean Interaction
    Experiment.............................................................................
    67

9.  Hurricane Synoptic
    Surveillance...............................................................................
    72

> **SUPPLEMENTAL: OPERATIONAL MAPS**

1.  Map 1: Primary Atlantic operating bases and operating ranges
    (G-IV).............................\...... 77

2.  Map 2: Primary Atlantic operating bases and operating ranges (P-3)
    .................................... 78

**2007 HURRICANE FIELD PROGRAM PLAN**

**INTRODUCTION**

National Oceanic and Atmospheric Administration

Atlantic Oceanographic and Meteorological Laboratory

Hurricane Research Division

Miami, Florida. USA

One of the key activities in the NOAA Strategic Plan Mission Goal 3
(Reduce Society's Risks from Weather and Water Impacts) is to improve
the understanding and prediction of tropical cyclones (TCs). The
National Centers for Environmental Prediction (NCEP) National Hurricane
Center (NHC) is responsible for forecasting TCs in the Atlantic and East
Pacific basins, while the Environmental Modeling Center (EMC) provides
NWP guidance for the forecasters. Together they have made great strides
in improving forecasts of TC track. With support from the research
community, forecast errors of TC track have decreased by about 50% over
the past 30 years. However, there has been much less improvement in
forecasts of TC intensity and rainfall. The lack of improvement in
intensity and rainfall forecasting is largely the result of deficiencies
in routinely collecting inner-core data and assimilating it into the
modeling system, limitations in the numerical models themselves, and
gaps in understanding of the physics of TCs and their interaction with
the environment. Accurate forecasts will rely heavily on the use of
improved numerical modeling systems, which in turn will rely on accurate
observational datasets for assimilation and validation.

The next-generation TC model, HWRF, is now operational. It runs at high
resolution (\~9 km), using improved physical parameterizations. Such a
configuration holds the hope of improving understanding and forecasting
of TC track, intensity, structure, and rainfall. In order to realize
such improvements, however, new data assimilation techniques must be
developed and refined, physical parameterizations must be improved and
adapted for TC environments, and the models must be reliably evaluated
against detailed observations from a variety of TCs and their
surrounding environments.

To conduct the research necessary to address the issues raised above,
NOAA has proposed an experiment designed to improve operational
forecasts of TC intensity, called the Intensity Forecasting EXperiment
(IFEX). The IFEX goals, developed through a partnership involving the
NOAA Hurricane Research Division (HRD), NHC, and EMC, are to improve
operational forecasts of TC intensity and rainfall by providing data to
improve the operational numerical modeling system (i.e., HWRF) and by
improving understanding of the physics of intensity change and rainfall.
These goals will be accomplished by satisfying a set of requirements and
recommendations guiding the collection of the data:

-   **Goal 1**: Collect observations that span the TC lifecycle in a
    variety of environments;

-   **Goal 2**: Develop and refine measurement technologies that provide
    improved real-time monitoring of

> TC intensity, structure, and environment;

-   **Goal 3**: Improve understanding of the physical processes
    important in intensity change for a TC at all stages of its
    lifecycle;

A unique, and critical, aspect of IFEX is the focus on providing
measurements of TCs at all stages of their life cycle, from pre-genesis
to intensification and subsequent landfall, decay over water, or
extratropical transition. The focus of hurricane research flights during
the past 25 years has been on mature storms, leading to a dataset biased
toward these types of systems. The strategy of observing the entire life
cycle of a TC is new and unique, and it will provide invaluable
information, particularly in sparsely observed environments.

The field program aircraft missions presented in this document are
separated into two distinct sections: 1) NHC and EMC operational
missions, and 2) HRD research experiments. The flight patterns that
comprise these various experiments and operational missions address
various aspects of the TC lifecycle, and they all specifically address
the main goals of IFEX.

The mission that will get the largest allotment of hours allocated to
HRD and NCEP is an operational mission (1), designed to improve the
forecast of hurricane structure and intensity by sampling the evolution
of tropical-cyclone structure and intensity using airborne Doppler
radar, SFMR, and dropwindsondes, from tropical depression to major
hurricane. Other experiments include 2) probing the evolution of
structure and intensity of TCs that make landfall, in particular
studying the weakening and dissipation of storms as they move inland, 3)
using the Aerosonde unmanned aircraft system (UAS) to sample the TC
environment, including the low-level regions of the TC boundary layer,
4) studying tropical cyclogenesis, 5) studying the ocean microwave
emissivity at angles of as much as 60 degrees from zenith, to permit a
scanning SFMR that will provide surface windspeeds over a wide swath
below the aircraft or a satellite, 6) understanding how propagating arc
clouds affect the evolution of African Easterly Waves (AEWs) or TCs, 7)
investigating the impact of the Saharan Air Layer (SAL) on TC intensity
change, 8) measuring sea-salt aerosol and cloud-base Cloud Condensation
Nuclei (CCN) number concentrations in TCs, 9) looking at eyewall droplet
and ice-particles size distribution and habits and water content with
new cloud-physics probes to improve microphysical parameterizations of
numerical simulations of TCs, 10) probing the interaction of the ocean
and atmosphere in TCs, and 11) an operational mission designed to
improve model forecasts of TC track by sampling the surrounding
tropical-cyclone environment. These experiments and operational missions
will be conducted with the two NOAA P-3s and Gulfstream IV-SP aircraft.
A summary of each, along with which IFEX goals it specifically
addresses, is included below. A detailed description of each experiment
or operational mission follows, including descriptions of the scientific
and details of the associated flight patterns.

**(1) Three-Dimensional Doppler Winds**: This is a multi-option,
single-aircraft operational mission designed to use the NOAA P-3 to
sample TCs ranging in intensity from tropical depression to a major
hurricane. The definition is meant to separate this category from
tropical waves and disturbances that have yet to develop a well-defined
warm-core circulation. The main goals of these missions is: 1) to
improve understanding of the factors leading to TC intensity and
structure changes, 2) to provide a comprehensive data set for the
initialization (including data assimilation) and validation of numerical
hurricane simulations (in particular HWRF), 3) to improve and evaluate
technologies for observing TCs, and 4) to develop rapid real-time
communication of these observations to NCEP. The overall experiment is
comprised of two parts: one designed to obtain regular 12- or 24-h
resolution airborne Doppler-radar observations of hurricanes, with
optional dropwindsondes, and one, the National Environmental Satellite,
Data, and Information Service (NESDIS) Ocean Winds and Rain Experiment,
designed to improve understanding of microwave surface scatterometery in
high-wind conditions over the ocean by collecting surface scatterometery
data and Doppler data in the boundary layer of hurricanes.

**(2) Tropical Cyclone Landfall and Inland Decay Experiment:** This is a
multi-option, single-aircraft experiment designed to study the changes
in TC surface wind structure near and after landfall. It has several
modules that could also be incorporated into operational surveillance or
reconnaissance missions. An accurate description of the TC surface wind
field is important for warning, preparedness, and recovery efforts. It
addresses IFEX Goals 1, 2, and 3.

**(3) Tropical Cyclone Unmanned Aerial System (UAS) Inflow/Eyewall/Eye
Experiment:** This is a multi-option, multi-aircraft experiment that
uses the Aerosonde UAS and dropwindsondes or aircraft expendable
bathythermographs (AXBTs) launched from the NOAA P-3 to fully
demonstrate and utilize the unique capabilities of the Aerosonde
platform to document areas of the TC environment that would otherwise be
either impossible or impractical to observe. It is planned that this
effort will be based in Barbados. The immediate focus is to document and
significantly improve understanding of the rarely observed TC boundary
layer and undertake detailed comparisons between in-situ and
remote-sensing observations obtained from manned aircraft (NOAA P-3 and
Air Force Reserve (AFRES) C-130) and satellite-based platforms. In
addition, a primary objective of this effort is to provide real-time,
near-surface wind observations to NHC in direct support of NOAA
operational requirements. These unique data will also be made available
to EMC for both model initialization and forecast verification purposes.
This addresses IFEX Goals 1, 2, and 3.

**(4) Tropical Cyclogenesis Experiment*: ***This multi-option,
multi-aircraft experiment is designed to study how a tropical
disturbance becomes a tropical depression with a closed surface
circulation. It seeks to answer the question through multilevel aircraft
penetrations using dropwindsondes, flight-level data, and radar
observations on the synoptic, mesoscale, and convective spatial scales.
It will focus particularly on dynamic and thermodynamic transformations
in the low- and mid-troposphere and lateral interactions between the
disturbance and its synoptic-scale environment. It addresses IFEX Goals
1 and 3.

**(5)** **Nadir Off-set** **SFMR** **Experiment:** This is a
single-aircraft experiment designed to obtain measurements off nadir of
the sea surface to help develop retrieval models for the HIRAD.

**(6) Tropical Cyclone/AEW Arc Cloud** **Experiment:** This is a
single-aircraft experiment, designed to collect observations across arc
cloud features in the periphery of an AEW or TC using aircraft
flight-level and dropwindsonde data to improve understanding of how
these features may limit short-term intensification. Observations could
be made using either the P-3 aircraft conducting another experiment, or
the G-IV during a synoptic surveillance mission.

**(7) Saharan Air Layer Experiment:** This is a multi-option,
multi-aircraft experiment which uses dropwindsondes launched from the
NOAA G-IV and NOAA P-3 to examine the thermodynamic and kinematic
structure of the SAL and its potential impact on TC genesis and
intensity change. The dropwindsonde release points will be selected
using real-time GOES SAL tracking imagery from UW-CIMSS and mosaics of
SSM/I total precipitable water from the Naval Research Laboratory.
Specific effort will be made to gather atmospheric information within
the SAL as well as regions of high moisture gradients across its
boundaries and the region of its embedded mid-level easterly jet. The
goals are to better understand and predict how the SAL dry air,
mid-level easterly jet, and suspended mineral dust affect Atlantic TC
intensity change and to assess how well these components of the SAL are
being represented in forecast models. It addresses IFEX Goals 1 and 3.

**(8)** **Sea-Salt Aerosol and Cloud Base Number Concentration**
**Experiment:** This single-aircraft experiment is a downwind flight leg
outside the eyewall in relatively clear air, or just inside the inner
edge of the eyewall. It will measure the concentrations of sea-salt
aerosol and CCN concentrations below cloud base (1200- to 2000-ft flight
levels are likely) in tropical storms and category 3 or less TCs, as
well as approximately 200 ft above cloud base.

**(9) Eyewall Microphysics** **Experiment:** This is a single-aircraft,
high-altitude penetration of eyewall convection, designed to document
the ice-phase microphysics of the eyewall better than ever before, to
benefit microphysical parameterizations in simulation of TCs. This could
improve modeling of precipitation production, thus accurately estimating
latent heat release (LHR) (affecting hurricane intensity) and rainfall
quantitative prediction. It is preferred that it be flown at or above
20,000 ft.

**(10) TC-Ocean Interaction Experiment:** This is a multi-option, single
aircraft experiment acting in support of upper ocean and air-sea flux
measurements made by oceanic floats and drifters. One to three float and
drifter arrays will be deployed into one or two mature storms by an AFRC
C-130J and provide real-time ocean data. A NOAA P-3 will deploy
dropwindsondes and make SFMR and Scanning Radar Altimeter (SRA)
measurements within the float and drifter array as the storm passes over
it. This work will be coordinated with NASA P-3 deployments of CTD
probes.

**(11) Hurricane Synoptic Surveillance**: This is a multi-option, single
or multi-aircraft operational mission that uses dropwindsondes launched
from the NOAA G-IV, and the AFRES C-130 to improve landfall predictions
of TCs by releasing dropwindsondes in the environment of the TC center.
These data will be used by NCEP to prepare objective analyses and
official forecasts through their assimilation into operational numerical
prediction models. Because the atmosphere is known to be chaotic, very
small perturbations to initial conditions in some locations can amplify
with time. However, in other locations, perturbations may result in only
small differences in subsequent forecasts. Therefore, targeting
locations in which the initial conditions have errors that grow most
rapidly may lead to the largest possible forecast improvements. Locating
these regions that impact the particular forecast is necessary. When
such regions are sampled at regularly spaced intervals the impact is
most positive. The optimal targeting and sampling strategies is an
ongoing area of research. This addresses IFEX Goal 1.

In addition to the experiments presented above that comprise IFEX,
several other are occurring simultaneously and will be partnering with
IFEX:

1.  NESDIS will be conducting the Ocean Winds Experiment, using N42RF
    for part of the season. The goal is to further understanding of the
    ocean surface wind vector retrievals in high windspeed conditions
    and in the presence of rain for all windspeeds from microwave
    remote-sensing measurements.

2.  EMC ran HWRF in operational mode for the first time in 2007. In
    addition a parallel run of HWRF will be run that assimilates the
    airborne Doppler observations. These will not be run simultaneously
    with the operational run but will be run soon thereafter to do an
    early evaluation of the assimilation of airborne Doppler
    observations.

3.  

4.  

**Operations**

**1. Locations**

Starting on 01 June, the P-3s and Gulfstream IV-SP aircraft will be
available for possible missions. Operations for both aircraft will
primarily base out of Tampa, Florida, with provision for deployments to
Barbados, St. Croix, and Bermuda for storms in the Atlantic basin
(including the Atlantic Ocean and the Caribbean Sea) and deployments to
U.S. coastal locations in the western Gulf of Mexico for suitable Gulf
storms. Occasionally, post mission recovery may be accomplished
elsewhere.

**2. Field Program Duration**

The hurricane field research program will be conducted from 01 June
through 30 September 2008.

**3. Research Mission Operations**

The decision and notification process for hurricane research missions is
shown, in flow chart form, in Appendix A (Figs. A-1, A-2, and A-3). The
names of those who are to receive primary notification at each decision
or notification point shown in Figs. A-1, A-2, and A-3 are also listed
in Appendix A. Contacts are also maintained each weekday among the
directors of HRD, NHC, EMC, and AOC.

Research operations must consider that the research aircraft are
required to be placed in the National Hurricane Operations Plan of the
Day (POD) 24 h before a mission. If operational requirements are
accepted, the research aircraft must follow the operational constraints
described in Section 7.

**4. Task Force Configuration**

The NOAA P-3 aircraft, equipped as shown in Appendix G, will be
available for research operations on a non-interference basis with
tasked operational missions from 01 June to 30 September 2008. Also, the
G-IV aircraft should be available, on a non-interference basis with
tasked operational missions from 01 June to 30 September 2008.

**5. Field Operations**

*5.1* *Scientific Leadership Responsibilities*

The implementation of the 2008 Hurricane Field Program Plan is the
responsibility of the field program director, who in turn, reports
directly to the HRD director. The field program director will be
assisted by the field program ground team manager. In the event of
deployment, the field program ground team manager shall be prepared to
assume overall responsibility for essential ground support logistics,
site communications, and site personnel who are not actively engaged in
flight. Designated lead project scientists are responsible to the field
program director or designated assistants. While in flight, lead project
scientists are in charge of the scientific aspects of the mission.

*5.2* *Aircraft Scientific Crews*

Tables B-2.1 through B-2.4 (Appendix B) list the NOAA scientific
crewmembers needed to conduct the experiments. Actual named assignments
may be adjusted on a case-by-case basis. Operations in 2008 will include
completion of detailed records by each scientific member while on the
aircraft. General checklists of NOAA science-related functions are
included in Appendix E.

*5.3* *Principal Duties of the Scientific Personnel*

A list of primary duties for each NOAA scientific personnel position is
given in Appendix D.

*5.4* *HRD Communications*

The Miami Ground Operations Center (MGOC) will operate from offices at
AOML on Virginia Key (4301 Rickenbacker Causeway, Miami, FL) or from NHC
(11691 S.W. 17th Street, Miami, FL). MGOC, operating from AOML or NHC,
will serve as the communications center for information and will provide
interface with AOC, NHC, and CARCAH (Chief, Aerial Reconnaissance
Coordinator, All Hurricanes). In the event of a deployment of aircraft
and personnel for operations outside Miami, the field program ground
team manager will provide up-to-date crew and storm status and schedules
through the field program director or the named lead project scientist.
Personnel who have completed a flight will provide information to MGOC,
as required.

**6. Data Management**

Data management and dissemination will be according to the HRD data
policy that can be viewed at:

<http://www.aoml.noaa.gov/hrd/data2.html>

A brief description of the primary data types and contact information
may be found at:

<http://www.aoml.noaa.gov/hrd/data/products.html>

Raw data are typically available to all of NOAA-sponsored personnel and
co-investigators immediately after a flight, subject to technical and
quality assurance limitations. Processed data or other data that has
undergone further quality control or analyses are normally available to
the principle and co-investigators within a period of several months
after the end of the Hurricane Field Program. Examples of
co-investigators are NASA-sponsored NAMMA investigators and associated
university or other Governmental partners.

All requests for NOAA data gathered during the 2008 Hurricane Field
Program should be forwarded by email to the associated contact person in
the HRD data products description (link above) or in writing to:
Director, Hurricane Research Division/AOML, 4301 Rickenbacker Causeway,
Miami, Florida 33149.

**7. Operational Constraints**

NOAA P-3 aircraft are routinely tasked by NHC through CARCAH to perform
operational missions that always take precedence over research missions.
Research objectives can frequently be met, however, on these operational
missions. Occasionally, HRD may request, through NHC and CARCAH, slight
modifications to the flight plan on operational missions. These requests
must not deter from the basic requirements of the operational flight as
determined by NHC and coordinated through CARCAH.

Hurricane research missions are routinely coordinated with hurricane
reconnaissance operations. As each research mission is entered into the
planned operation, a block of time is reserved for that mission and
operational reconnaissance requirements are assigned. A mission, once
assigned, *must be flown in the time period allotted and the tasked
operational fixes met.* Flight departure times are critical. Scientific
equipment or personnel not properly prepared for the flight at the
designated pre-take-off time will remain inoperative or be left behind
to insure meeting scheduled operational fix requirements. Information on
delays to or cancellations of research flights must be relayed to
CARCAH.

**8. Calibration of Aircraft Systems**

Calibration of aircraft systems is described in Appendix B (B.1 en-route
calibration of aircraft systems). True airspeed (TAS) calibrations are
required for each NOAA flight, both to and from station and should be
performed as early and as late into each flight as possible (Fig. B-1).

**IFEX Missions**

**1.** **Three-Dimensional Doppler Winds**

**Program significance:** This experiment is a response to the
requirement listed as Core Doppler Radar in Section 5.4.2.9 of the
National Hurricane Operations Plan. The goal of that particular mission
is to gather airborne-Doppler wind measurements that permit an accurate
initialization of HWRF, and also provide three-dimensional wind analyses
for forecasters.

There are four main goals: 1) to improve understanding of the factors
leading to TC intensity and structure changes, 2) to provide a
comprehensive data set for the initialization (including data
assimilation) and validation of numerical hurricane simulations (in
particular HWRF), 3) to improve and evaluate technologies for observing
TCs, and 4) to develop rapid real-time communication of these
observations to NCEP.

The ultimate requirement for EMC is to obtain the three-dimensional wind
field of Atlantic TCs from airborne Doppler data every 6 h to provide an
initialization of HWRF through assimilation every 6 h. In 2008, the
maximum possible rotation of missions is two per day or every 12 h. In
hurricanes, coordination will be required between HRD, NCEP, and NESDIS,
to effectively collect observations for both the Three-Dimensional
Doppler Winds Experiment and the Ocean Winds and Rain Experiment, a
NESDIS program designed to improve understanding of microwave surface
scatterometery in high-wind conditions over the ocean by collecting
surface scatterometery data and Doppler data in the boundary layer of
hurricanes.

The highest vertical resolution is needed in the boundary and outflow
layers. This is assumed to be where the most vertical resolution is
needed in observations to verify the initialization and model. For this
reason it is desirable that if sufficient dropwindsondes are available,
they should be deployed in the radial penetrations in the
Three-Dimensional Doppler Winds experiment to verify that the
boundary-layer and surface wind forecasts produced by HWRF resemble
those in observations. These observations will also supplement airborne
Doppler observations, particularly in sectors of the storm without
sufficient precipitation for radar reflectivity. If sufficient
dropwindsondes are not available, a combination of SFMR, Advanced Wind
and Rain Airborne Profiler (AWRAP), and airborne Doppler data will be
used for verification.

**NESDIS Ocean Winds and Rain Experiment**: This will be executed by
NESDIS and aims to improve understanding of microwave scatterometer
retrievals of the ocean surface wind. The NESDIS/Office of Research and
Applications in conjunction with the University of Massachusetts (UMASS)
Microwave Remote Sensing Laboratory and AOC have been conducting flights
as part this experiment for the past several years. It is part of an
ongoing field program whose goal is to further understanding of
microwave scatterometer and radiometer retrievals of the ocean surface
wind vector in high windspeed conditions and in the presence of rain for
all windspeeds. This knowledge will be used to help improve and
interpret operational wind retrievals from current and future
satellite-based scatterometers. The hurricane environment provides the
adverse atmospheric and ocean surface conditions required. The AWRAP and
the SFMR (USFMR), both designed and built by UMASS, are the critical
sensors. AWRAP consists of two scatterometers operating at Ku-band and
C-band, which measure the reflectivity profile in precipitation in
addition to the surface backscatter. The capabilities of AWRAP are
essential in unraveling the effects of precipitation on scatterometer
wind retrievals. A raw data mode acquisition system was tested for AWRAP
during the Winter Storms Experiment this year, and it will be fully
implemented during this hurricane season. Collecting the raw data allows
spectral processing to be done which will allow the rain and surface
contributions in the AWRAP data to be decoupled. This is critical in
understanding the impacts of rain on the measurements, and thus, the
ocean surface wind vector retrievals.

A secondary objective of NESDIS is to explore how much of this remotely
sensed data collected on the P-3 can be processed and sent off the plane
in near real time. NESDIS has been working with Remote Sensing
Solutions, Inc. in developing an effective data processing, distribution
and display system to accomplish this within the constraints of a
satellite phone data connection. AOC and HRD have been integral partners
in accomplishing this task. Remotely sensed surface data is not only
extremely useful for flight planning but also to the hurricane analysts
at the Tropical Prediction Center as has been demonstrated with the use
of the SFMR on the P-3s and C130s. The P-3s are equipped with a
dedicated Globalstar satellite phone and a computer system to process
and distribute to the ground the flight-level serial data stream and the
lower fuselage radar data in near real time. A second Globalstar
satellite data connection will be used to test dissemination of products
derived from the X-band tail radar, a near real-time processing system
for AWRAP and USFMR, and the serial data stream from the AVAPS station.
The transmission of full resolution tail radar data packets may also be
tested if a higher bandwidth satellite phone system becomes available.

**Links to IFEX: The Three-Dimensional Doppler Winds experiment supports
the following NOAA IFEX goals:**

-   **Goal 1**: Collect observations that span the TC lifecycle in a
    variety of environments

-   **Goal 2**: Develop and refine measurement technologies that provide
    improved real-time monitoring of

> TC intensity, structure, and environment

-   **Goal 3**: Improve understanding of the physical processes
    important in intensity change for a TC at all stages of its
    lifecycle

-   

-   

-   

**Mission Descriptions:**

The NESDIS Ocean Winds and Rain Experiment will be executed by NESDIS.
Specific details regarding these NESDIS missions are not included here.

**Three-Dimensional Doppler Winds:** Several different options are
possible: 1) the lawnmower pattern (Fig. TDDW-1), 2) the box-spiral
pattern (Figs. TDDW-2 and TDDW-3), 3) the rotating figure-4 pattern
(Fig. TDDW-4), 4) the butterfly pattern that consists of 3 penetrations
across the storm center at 60-degree angles with respect to each other
(Fig. TDDW-5), and 5) the single figure-4 (Fig. TDDW-6). These patterns
provide the maximum flexibility in planning, in which the need for dense
date coverage must be balanced against the need to sample the entire
vortex.

*Single-aircraft option only:* Temporal resolution (here defined as data
collected as close as possible to a 6-h interval as possible) is
important, for both initialization and verification of HWRF. This has
been verified in communication with EMC. In 2008, to obtain the maximum
temporal resolution feasible, this mission is expected to be a
single-P-3 mission, to allow another crew to operate 12 h later, and to
continue in a 12-h cycle of sorties. The type of flight pattern will be
determined from the organization, strength and radial extent of the
circulation.

**Lawnmower** **pattern**: This pattern will be chosen for systems with
small, weak, newly developed circulations, namely tropical depressions
and weak tropical storms. If the system is small enough, lawnmower
pattern A (Fig. TDDW-1) will be chosen, to permit complete coverage of
all reflectors within the developing circulation. Otherwise pattern B
will be flown. Pattern B permits a larger area to be sampled, at the
expense of some gaps in the Doppler coverage. A specific flight level is
not required for this mission. It is likely that the Air Force will be
flying at an investigation level at this time, and the Three-Dimensional
Doppler Winds Experiment can be flown anywhere from 5,000 ft to 14,000
ft. If detailed thermodynamic data from dropwindsondes is desirable, or
the distribution of Doppler winds is highly asymmetric, then the
preferred level would be 14,000 ft to allow the deepest observation of
the thermodynamic and wind structure from the dropwindsondes, while
reducing the likelihood of lightning strikes by staying below the
melting level. Any orientation of the long and short flight legs may be
flown, to permit the location of the initial and final points to be
closest to the base of operations.

**Box-spiral** **pattern**: As the weak, developing, poorly organized
circulations become larger, it will be necessary to spread out the
pattern to cover a larger area at the expense of complete Doppler
coverage. Pattern A, as shown in Fig. TDDW-2, is designed to cover a box
280 nm x 280 nm with radial gaps in the coverage. As long as the
circulation is still weak, but covers a larger area, this pattern will
be considered; however, lack of symmetric coverage at all radii render
this a less viable option as the system organizes. Pattern B has denser
coverage within the outside box, and it will be considered in smaller
systems. Any orientation of the flight legs may be flown, to permit the
location of the initial and final points to be closest to the base of
operations.

**Rotating** **figure-4** **pattern**: As the system intensity and/or
organization increases, and a circulation center becomes clearly
defined, a rotating figure-4 pattern may be preferred (Fig. TDDW-4). The
advantage of this pattern over the larger versions of the lawnmower
pattern is symmetric wind coverage, and the advantage over the
box-spiral pattern is good definition of the wind field at all radii
within the pattern. This pattern is obviously preferable to the
lawnmower pattern in the event there is any operational fix
responsibility for the aircraft. Any orientation of the flight legs may
be flown, to permit the location of the initial and final points to be
closest to the base of operations. See discussion of "lawnmower pattern"
regarding flight altitude and use of dropwindsondes.

**Butterfly** **pattern**: This pattern (Fig. TDDW-5) should be flown in
larger, well-organized TCs, generally in hurricanes. As the hurricane
circulation becomes larger, it will be necessary to get the full radial
coverage at the expense of full Doppler coverage. As an example, a
butterfly pattern out to 100 nm could be flown in 3.3 h, compared to a
similar lawnmower coverage that would take 4.8 h. This pattern is
obviously preferable to the lawnmower pattern in the event there is any
operational fix responsibility for the aircraft. Any orientation of the
flight legs may be flown, to permit the location of the initial and
final points to be closest to the base of operations. See discussion of
"lawnmower pattern" regarding flight altitude and use of dropwindsondes.

**Single** **figure-4** **pattern**: This pattern (Fig. TDDW-6) will be
flown in very large circulations. It still provides wavenumber 0 and 1
coverage with airborne Doppler data, which should be sufficient in
strong, organized systems. Radial coverage out to 240 and 300 nm (4 and
5 degrees) is possible in 5.4 and 6.8 h in pattern. Any orientation of
the flight legs may be flown, to permit the location of the initial and
final points to be closest to the base of operations. See discussion of
"lawnmower pattern" regarding flight altitude and use of dropwindsondes.

**Three-Dimensional Doppler Winds Experiment Flight Planning Approach:**
NOAA will conduct a set of flights during several consecutive days,
encompassing as much of a particular storm life cycle as possible. This
would entail using the two available P-3s on back-to-back flights on a
12-h schedule when the system is at depression, tropical storm, or
hurricane strength.

At times when more than one system could be flown, one may take
precedence over others depending on factors such as storm strength and
location, operational tasking, and aircraft availability. All other
things being equal, the target will be an organizing tropical depression
or weak tropical storm, to increase the observations available in these
systems. One scenario could likely occur that illustrate how the mission
planning is determined: an incipient TC, at depression or weak tropical
storm stage is within range of an operational base and is expected to
develop and remain within range of operational bases for a period of
several days. Here, the highest priority would be to start the set of
Three-Dimensional Doppler Winds flights, with single-P-3 missions, while
the TC is below hurricane strength (preferably starting at depression
stage), with continued single-P-3 missions at 12-h intervals until the
system is out of range or makes landfall. During the tropical depression
or tropical-storm portion of the vortex lifetime, higher azimuthal
resolution of the wind field is preferred over radial extent of
observations, while in the hurricane portion, the flight plan would be
designed to get wavenumber 0 and 1 coverage of the hurricane out to the
largest radius possible, rather then the highest time resolution of the
eyewall. In all cases maximum spatial coverage is preferred over
temporal resolution during one sortie.

**Tropical Cyclone Eye Mixing Module:** Eyewall mesovortices have been
hypothesized to mix high entropy air from the eye into the eyewall, thus
increasing the amount of energy available to the hurricane. Signatures
of such mesovortices have been seen in cloud formations within the eyes
of very strong TCs, and from above during aircraft penetrations.
Observations within the eye below the inversion can allow for the study
of the dynamic and thermodynamic structures of these mesovortices and
improve knowledge of small-scale features and intensity changes in very
strong TCs.

Although this is not a standalone experiment, it could be included
within any of the following missions: SALEX, Aerosonde Experiment, or TC
Landfall and Inland Decay Experiment. A Category 4 or 5 TC with a
clearly defined eye and eyewall and an eye diameter of at least 25 nm is
needed (Fig. TDDW-7). The P-3 will penetrate the eyewall at the altitude
proposed for the rest of the flight. Once inside the eye, the P-3 will
descend from that altitude to a safe altitude below the inversion (about
2500 ft) while performing a figure-4 pattern. The leg lengths will be
determined by the eye diameter, with the ends of the legs at least 2 nm
from the edge of the eyewall. Upon completion of the descent, the P-3
will circumnavigate the eye about 2 nm from the edge of the eyewall in
the shape of a pentagon or hexagon. Time permitting; another figure-4
will be performed during ascent to the original flight level. Depending
upon the size of the eye, this pattern should take between 0.5 and 1 h.

**Eyewall Sampling and Intensity Change Module:** Hurricane intensity,
defined by either minimum sea-level pressure or maximum sustained
windspeed, is determined by processes in the core (radial distance \<
100 km). These processes include, but are not limited to, enhanced sea
to air fluxes near and under the eyewall, eye-eyewall mixing, convective
outbreaks in the eyewall, increased mass and moisture inflow to the
eyewall, contraction of the eyewall, and the interaction of the
upper-level flow with the eyewall. To more fully understand these
processes the research community needs detailed monitoring of the core
of several hurricanes. The observations can also serve some real-time
needs of NHC.

Dropwindsondes, when combined with the TC track, will allow the
calculation of storm-relative variables. Each dropwindsonde will provide
estimates of inflow rate and depth, and energy content. These profiles
are then assembled to construct an azimuth-height surface that extends
from a few hundred meters below aircraft altitude to the sea surface
around the eyewall. The azimuth-height surface allows the estimation of
fluxes of mass, moisture, and energy flux to the eyewall for the entire
inflow. If the module is repeated at other radii (e.g., 100 km or just
inside the eyewall), net vertical transports through a given altitude,
or net fluxes through the sea surface can be determined using divergence
to infer processes between the two surfaces. The surface fluxes may be
solved as a residual or estimated using the data collected at 10 m by
the dropwindsonde. Mixing across the top surface remains an issue, but
if the aircraft is equipped with turbulence sensors, this exchange can
be determined.

The plan views of the eyewall region from the lower fuselage radar are
used to estimate net LHR. As the aircraft moves around the eyewall it
will get views of each quadrant. These quadrants are assembled for a
complete view of the eyewall region that limits beam filling or
attenuation issues. A Z-R relationship is then applied to this map of
reflectivity to estimate LHR. LHR can be compared to other standard
measures of TC intensity such as MSLP and maximum sustained windspeeds
estimated from the aircraft. LHR has the advantage that it does not rely
on a single pass or reading, instead it is the integration of the net
LHR from the entire eyewall region. The lower fuselage radar also
reveals if the eyewall consists of one or more cumulonimbus clouds, is
more mesoscale, or is asymmetric. The tail radar provides estimates of
echo top, and echo slope. These also serve as measures of TC intensity
-- higher, less sloped systems expected for higher category TCs. As the
aircraft circumnavigates the eyewall F/AST can be applied. F/AST
provides approximately 2-km horizontal resolution wherever there are
scatterers. Continuity applied to these windfields results in an
estimate of the vertical velocity field. The dropwindsondes provide data
that can be used as an initial condition for the lowest 500 m where sea
clutter may contaminate the Doppler wind estimates.

The pattern is a circumnavigation around the eyewall with the P-3 flying
counterclockwise to exploit strong tailwinds (Fig. TDDW-8). The aircraft
would maintain a \~10 km separation from the eyewall that places the
aircraft in an excellent position to obtain tail radar data for both
reflectivity and Doppler wind measurements. Altitude may be 8500 feet to
11,500 feet (750 to 650 hPa). Circumnavigation around the eyewall can be
done relatively quickly, on the order of one-half hour, for an eyewall
radius of about 35 km. About 12 dropwindsondes would be deployed during
circumnavigation that provides estimates of the depth, rate and
thermodynamics of the inflow. AXBTs should also be deployed at points 1,
5, 8, and 11. The circumnavigation can be done as part of the standard
figure-4 pattern used routinely during reconnaissance missions and often
at the start and finish of research missions.

There are several possible variations. More dropwindsondes could be
released in the eyewall in rapid succession. It would also be possible
to do multiple rings. For hurricanes with a large eyewall a
circumnavigation along the inner edge of the eyewall would be possible
to ascertain more about the interaction of the eye and eyewall. More
distant circumnavigations allow for an assessment of where the inflow is
gaining or losing energy as the inflow approaches the eyewall.
Complementary sampling could be done with the Aerosonde.

**Three-Dimensional Doppler Winds**

![](media/image3.jpeg){width="5.560416666666667in"
height="2.498611111111111in"}

![](media/image4.jpeg){width="5.08125in" height="2.498611111111111in"}

Figure TDDW-1. Display of Doppler coverage for A (upper panel) and B
(lower panel) lawnmower patterns shown in Figs. TDDW-1 and TDDW-2. Pink
region shows areas where vertical beam resolution is better than 0.7 km
and gray regions delineate areas where vertical beam resolution is
better than 1.4 km. Maximum extent of gray area is approximately 40 km
from flight track, generally the maximum usable extent of reliable
airborne Doppler radar coverage. Total flight distance is 1160 nm for A
and 1140 nm for B, and flight times are 4.8 and 4.75 hours,
respectively.

> Note 1. This is to be flown where even coverage is required,
> particularly in tropical depressions and tropical storms. Aircraft
> flies IP-2-3-4-5-6-7-FP. No attempt should be made to fix a center of
> circulation unless requested it is an operational request.
>
> Note 2. Doppler radars should be operated in single-PRF mode, at a PRF
> of 2400-3200. The default will be 2400 PRF. Radar scientist should
> verify this mode of operation with AOC engineers. If there is no
> assigned radar scientist, LPS should verify. *This is crucial for the
> testing and implementation of real-time quality control.*
>
> Note 3. Unless specifically requested by the LPS, both tail Doppler
> radars should be operated in F/AST with a fore/aft angle of 20 degrees
> relative to fuselage. French antenna automatically operates in F/AST,
> but it should be confirmed, nevertheless that the scanning is
> continuous, rather than sector scanning.
>
> Note 4. IP can be at any desired heading relative to storm center
>
> Note 5. To maximize dropwindsonde coverage aircraft should operate at
> highest altitudes that still minimize icing
>
> Note 6. If dropwindsondes are not deployed, aircraft can operate at
> any level below the melting level, with 10,000 ft preferred.
>
> Note 7. Dropwindsondes shown are not a required part of this flight
> plan and are optional.
>
> Note 8. Flight pattern should be centered around either the 18, 00,
> 06, or 12 UTC operational model analysis times.

**Three-Dimensional Doppler Winds**

![](media/image5.jpeg){width="6.684722222222222in"
height="3.872916666666667in"}

Figure TDDW-2. Doppler radar coverage for box-spiral pattern A. Pink
region shows areas where vertical beam resolution is better than 0.7 km
and gray regions delineate areas where vertical beam resolution is
better than 1.4 km. Maximum extent of gray area is approximately 40 km
from flight track, approximately the maximum usable extent of reliable
airborne Doppler radar coverage. Flight distance in pattern above is
1280 nm, and flight time is 5.33 hours.

> Note 1. This is to be flown where even coverage is required,
> particularly in tropical depressions and tropical storms. Aircraft
> flies IP-2-3-4-5-6-7-8-FP. No attempt should be made to fix a center
> of circulation unless requested it is an operational request.
>
> Note 2. Doppler radars should be operated in single-PRF mode, at a PRF
> of 2400-3200. The default will be 2400 PRF. Radar scientist should
> verify this mode of operation with AOC engineers. If there is no
> assigned radar scientist, LPS should verify. *This is crucial for the
> testing and implementation of real-time quality control.*
>
> Note 3. Unless specifically requested by the LPS, both tail Doppler
> radars should be operated in F/AST with a fore/aft angle of 20 degrees
> relative to fuselage. French antenna automatically operates in F/AST,
> but it should be confirmed, nevertheless that the scanning is
> continuous, rather than sector scanning.
>
> Note 4. IP can be at any desired heading relative to storm center
>
> Note 5. To maximize dropwindsonde coverage aircraft should operate at
> highest altitudes that still minimize icing
>
> Note 6. If dropwindsondes are not deployed, aircraft can operate at
> any level below the melting level, with 10,000 ft preferred.
>
> Note 7. Dropwindsondes shown are not a required part of this flight
> plan and are optional.
>
> Note 8. Flight pattern should be centered around either the 18, 00,
> 06, or 12 UTC operational model analysis times.

**Three-Dimensional Doppler Winds**

![](media/image6.jpeg){width="4.352083333333334in"
height="2.498611111111111in"}

![](media/image7.jpeg){width="4.227083333333334in"
height="2.498611111111111in"}

Figure TDDW-3. Doppler radar coverage for box-spiral pattern with 200-
(top) and 240- (bottom) nm legs. Pink region shows areas where vertical
beam resolution is better than 0.7 km and gray regions delineate areas
where vertical beam resolution is better than 1.4 km. Maximum extent of
gray area is approximately 40 km from flight track, approximately the
maximum usable extent of reliable airborne Doppler radar coverage. Upper
pattern is 1250 nm and uses 5.2 hours, while lower pattern is 1500 nm
and uses 6.25 hours.

> Note 1. This is to be flown where even coverage is required,
> particularly in tropical depressions and tropical storms. Doppler
> radars should be operated in single-PRF mode, at a PRF of 2400-3200.
> The default will be 2400 PRF. Radar scientist should verify this mode
> of operation with AOC engineers. If there is no assigned radar
> scientist, LPS should verify. *This is crucial for the testing and
> implementation of real-time quality control.*
>
> Note 2. Unless specifically requested by the LPS, both tail Doppler
> radars should be operated in F/AST with a fore/aft angle of 20 degrees
> relative to fuselage.
>
> Note 3. IP can be at any desired heading relative to storm center
>
> Note 4. To maximize dropwindsonde coverage aircraft should operate at
> highest altitudes that still minimize icing
>
> Note 5. Shaded areas show airborne-Doppler radar coverage with a
> maximum flight radius of 100 nm
>
> Note 6. Maximum radius may be decreased or increased within
> operational constraints
>
> Note 7. Dropwindsondes shown are not a required part of this flight
> plan and are optional.
>
> Note 8. Flight pattern should be centered around either the 18, 00,
> 06, or 12 UTC operational model analysis times.
>
> Note 9. Maximum radius may be changed to meet operational needs while
> conforming to flight-length constraints.

**Three-Dimensional Doppler Winds**

![](media/image8.jpeg){width="3.3319444444444444in"
height="2.498611111111111in"}

![](media/image9.jpeg){width="3.3319444444444444in"
height="2.498611111111111in"}

Figure TDDW-4. Doppler radar coverage for radial extents of 100 (top)
and 120 (bottom) nm of the rotating figure-4 patterns. Pink region shows
areas where vertical beam resolution is better than 0.7 km and gray
regions delineate areas where vertical beam resolution is better than
1.4 km. Maximum extent of gray area is approximately 40 km from flight
track, approximately the maximum usable extent of reliable airborne
Doppler radar coverage. Flight distances for 100, 120 and 150 nm radial
extents are 1160, 1395, and 1745 nm. Corresponding flight times are:
4.8, 5.8, and 7.3 h.

**Three-Dimensional Doppler Winds**

![](media/image10.jpeg){width="3.3319444444444444in"
height="2.498611111111111in"}

Figure TDDW-4 continued. Doppler radar coverage for 150-nm legs for a
rotating figure-4. Flight distances for 100, 120 and 150 nm radial
extents are 1160, 1395, and 1745 nm. Corresponding flight times are:
4.8, 5.8, and 7.3 h.

> Note 1. This pattern should be flown in strong tropical storms and
> hurricanes, where the circulation extends from 100 nm to 150 nm from
> the center. Doppler radars should be operated in single-PRF mode, at a
> PRF of 2400-3200. The default will be 2400 PRF. Radar scientist should
> verify this mode of operation with AOC engineers. If there is no
> assigned radar scientist, LPS should verify. *This is crucial for the
> testing and implementation of real-time quality control.*
>
> Note 2. Unless specifically requested by the LPS, both tail Doppler
> radars should be operated in F/AST with a fore/aft angle of 20 degrees
> relative to fuselage.
>
> Note 3. IP can be at any desired heading relative to storm center
>
> Note 4. To maximize dropwindsonde coverage aircraft should operate at
> highest altitudes that still minimize icing
>
> Note 5. Shaded areas show airborne-Doppler radar coverage with a
> maximum flight radius of 100 nm
>
> Note 6. Maximum radius may be decreased or increased within
> operational constraints
>
> Note 7. Dropwindsondes shown are not a required part of this flight
> plan and are optional.
>
> Note 8. Flight pattern should be centered around either the 18, 00,
> 06, or 12 UTC operational model analysis times.
>
> Note 9. Maximum radius may be changed to meet operational needs while
> conforming to flight-length constraints.

**Three-Dimensional Doppler Winds**

![](media/image11.jpeg){width="3.665277777777778in"
height="2.498611111111111in"}

![](media/image12.jpeg){width="3.748611111111111in"
height="2.498611111111111in"}

Figure TDDW-5. Doppler radar coverage for 120- (top) and 180- (bottom)
nm legs for the Butterfly pattern. Pink region shows areas where
vertical beam resolution is better than 0.75 km and gray regions
delineate areas where vertical beam resolution is better than 1.5 km.
Maximum extent of gray area is approximately 40 km from flight track,
approximately the maximum usable extent of reliable airborne Doppler
radar coverage. Flight distances for the patterns with 120 and 180 nm
radials legs are 960 and 1440 nm. Corresponding flight durations are 4
and 6 h.

> Note 1. This pattern will be flown in large tropical storms, as well
> as hurricanes. Doppler radars should be operated in single-PRF mode,
> at a PRF of 2400-3200. The default will be 2400 PRF. Radar scientist
> should verify this mode of operation with AOC engineers. If there is
> no assigned radar scientist, LPS should verify. *This is crucial for
> the testing and implementation of real-time quality control.*
>
> Note 2. Unless specifically requested by the LPS, both tail Doppler
> radars should be operated in F/AST with a fore/aft angle of 20 degrees
> relative to fuselage.
>
> Note 3. IP can be at any desired heading relative to storm center
>
> Note 4. To maximize dropwindsonde coverage aircraft should operate at
> highest altitudes that still minimize icing
>
> Note 5. Shaded areas show airborne-Doppler radar coverage with a
> maximum flight radius of 100 nm
>
> Note 6. Maximum radius may be decreased or increased within
> operational constraints
>
> Note 7. Dropwindsondes shown are not a required part of this flight
> plan and are optional.
>
> Note 8. Flight pattern should be centered around either the 18, 00,
> 06, or 12 UTC operational model analysis times.
>
> Note 9. Maximum radius may be changed to meet operational needs while
> conforming to flight-length constraints.

**Three-Dimensional Doppler Winds**

![](media/image13.jpeg){width="4.0in" height="2.609722222222222in"}

![](media/image14.jpeg){width="3.998611111111111in"
height="2.607638888888889in"}

Figure TDDW-6. Doppler radar coverage for 300-nm legs for a single
figure-4 pattern. Pink region shows areas where vertical beam resolution
is better than 0.75 km and gray regions delineate areas where vertical
beam resolution is better than 1.5 km. Maximum extent of gray area is
approximately 40 km from flight track, approximately the maximum usable
extent of reliable airborne Doppler radar coverage. Flight distances for
radial extents of 240 and 300 nm are 1300 and 1645 nm, respectively.
Corresponding flight times are 5.4 and 6.8 h.

> Note 1. This pattern should be flown for large storms, to obtain as
> full a radial extent of observations of the full storm circulation as
> possible. Doppler radars should be operated in single-PRF mode, at a
> PRF of 2400-3200. The default will be 2400 PRF. Radar scientist should
> verify this mode of operation with AOC engineers. If there is no
> assigned radar scientist, LPS should verify. *This is crucial for the
> testing and implementation of real-time quality control.*
>
> Note 2. Unless specifically requested by the LPS, both tail Doppler
> radars should be operated in F/AST with a fore/aft angle of 20 degrees
> relative to fuselage.
>
> Note 3. IP can be at any desired heading relative to storm center
>
> Note 4. To maximize dropwindsonde coverage aircraft should operate at
> highest altitudes that still minimize icing
>
> Note 5. Shaded areas show airborne-Doppler radar coverage with a
> maximum flight radius of 100 nm
>
> Note 6. Maximum radius may be decreased or increased within
> operational constraints
>
> Note 7. Dropwindsondes shown are not a required part of this flight
> plan and are optional.
>
> Note 8. Flight pattern should be centered around either the 18, 00,
> 06, or 12 UTC operational model analysis times.
>
> Note 9. Maximum radius may be changed to meet operational needs while
> conforming to flight-length constraints.

**IFEX Experiment (Continued)**

![](media/image15.jpeg){width="3.486111111111111in"
height="3.4916666666666667in"}

> Figure TDDW-7: The P-3 approaches from the north, penetrates the
> eyewall into the eye, and descends below the inversion to 2500 ft
> while performing a figure-4 (dotted line) in the eye. The P-3
> circumnavigates the eye in an octagon or pentagon (solid line), and
> then ascends while conducting another figure-4 (time permitting)
> rotated 45 degrees from the original (dashed line).

![](media/image16.png){width="5.998611111111111in"
height="3.388888888888889in"}

> Fig. TDDW-8. Flight track (bold line), eyewall (gray region), and GPS
> dropwindsondes (numbered).

**IFEX Missions** **(Continued)**

**2.** **Tropical Cyclone Landfall and Inland Decay**

**Program Significance:** The lifecycle of a TC often ends when it makes
landfall and decays as it moves inland. During a hurricane threat, an
average of 300 nm (550 km) of coastline is placed under a hurricane
warning, which costs about \$50 million in preparation per event. The
size of the warned area depends on the extent of hurricane and tropical
storm-force windspeeds at the surface, evacuation lead-times, and the
forecast of the storm track. Research has helped reduce uncertainties in
the track and landfall forecasts, and now one of the goals of IFEX is to
improve the accuracy of the surface wind fields in TCs, especially near
and after landfall. Improvements in diagnosing surface wind fields could
decrease the uncertainty of the size of the hurricane warning area
thereby reducing the cost of preparing for a landfalling hurricane.

There are still uncertainties in deriving surface wind estimates from
flight-level and SFMR windspeeds collected near the coast. Changing
bathymetry could change the breaking wave field, which could change both
the roughness length at higher windspeeds as well as changing the
microwave emissions. Evaluation of these effects may lead to adjustments
to the operational surface windspeed algorithms. Data collected at the
coast will also help to refine the Kaplan/DeMaria inland decay model
that has been developed as part of a recently completed Joint Hurricane
Testbed (JHT) project. Airborne Doppler radar data will be also be
transmitted to NCEP as part of another completed JHT project to
assimilate radar data into the HWRF model.

Analysis of Doppler radar, GPS dropwindsonde, SFMR, flight-level and SRA
or AWRAP data collected during hurricane flights can help achieve the
IFEX goals for the 2008 Hurricane Field Program. A major goal is to
capture the lifecycle of a TC and while landfall is usually at the end
of the lifecycle the same data collection strategies developed for
mature hurricanes over the open ocean can also be applied at landfall.
Subsets of the data collected can be transmitted to NHC and to EMC, for
assimilation into HWRF. The Doppler and GPS dropwindsonde data can be
analyzed to derive three-dimensional windfields to compare with output
from the HWRF and data from the SRA can be compared to HWRF wavefields.
In addition to shear and heat flux from the ocean, hurricanes at
landfall experience other conditions that may affect intensity change.
These include change in ocean wave action in shallow waters, change in
surface roughness, drier and cooler inflow from the land, and
topography. Radar, dropwindsonde, and SFMR data can help define those
conditions. Decay over land is also important and data collected during
and shortly after landfall should help refine both operational
statistical decay models (such as the Kaplan/DeMaria model) and
3-dimensional numerical models like HWRF.

HRD developed a real-time surface wind analysis system to aid NHC in the
preparation of warnings and advisories in TCs. The surface wind analyses
are now used for post-storm damage assessment by emergency management
officials and to validate and calibrate the Kaplan/DeMaria decay model.
These wind analyses could also be used to initialize the operational
storm surge model in real time.

As a TC approaches the coast, surface marine wind observations are
normally only available in real time from National Data Buoy Center
moored buoys, Coastal-Marine Automated Network (C-MAN) platforms, and a
few ships. Surface wind estimates must therefore be based primarily on
aircraft measurements. Low-level (\<5,000 ft \[1.5 km\] altitude) NOAA
and AFRES aircraft flight-level windspeeds are adjusted to estimate
surface windspeeds. These adjusted windspeeds, along with C-SCAT and
SFMR wind estimates, are combined with actual surface observations to
produce surface wind analyses. These surface wind analyses were
initially completed after the landfall of Hurricane Hugo in South
Carolina and of Andrew in South Florida in support of post-landfall
damage surveys conducted by FEMA. In recent years, these analyses have
been produced in real time for operational use by the NHC for many of
the TCs that have affected the Western Atlantic basin, including such
notable landfalling storms as Opal (1995), Fran (1996), Georges (1998),
Bret and Floyd (1999), Isidore (2003) and Frances, Ivan and Jeanne
(2004), and Dennis, Katrina, Rita and Wilma (2006).

Dual-Doppler analysis provides a complete description of the wind field
in the core. Recently the analysis techniques have been streamlined so
real-time wind analyses can be computed aboard the aircraft and
windfields at selected levels transmitted from the aircraft to NHC and
NMC. These windfields are also quite useful for post-storm analysis. An
observational study of Hurricane Norbert (1984), using a PDD analysis of
airborne radar data to estimate the kinematic wind field, found radial
inflow at the front of the storm at low levels that switched to outflow
at higher levels, indicative of the strong shear in the storm
environment. Another study used PDD data collected in Hurricane Hugo
near landfall to compare the vertical variation of windspeeds over water
and land. The profiles showed that the strongest windspeeds are often
not measured directly by reconnaissance aircraft.

Recent GPS dropwindsonde data from near and inside the flight-level
radius of maximum windspeeds (RMW) in strong hurricanes have shown
remarkable variations of the wind with height. A common feature is a
windspeed maximum at 300-500 m altitude. Theoretical and numerical
modeling of the hurricane boundary layer suggests that the low-level
jets are common features. The height of the jet varies by storm
quadrant, and modeling indicates that this variation can be enhanced as
a hurricane crosses land.

While collection of dual-Doppler radar data by aircraft alone requires
two P-3 aircraft flying in well-coordinated patterns, time series of
dual-Doppler data sets have been collected by flying a single P-3 toward
or away from a ground-based Doppler radar. In that pattern, the aircraft
Doppler radar rays are approximately orthogonal to the ground-based
Doppler radar rays, yielding true Dual-Doppler coverage. Starting in
1997 the Atlantic and Gulf coasts were covered by a network of Doppler
radars (Weather Surveillance Radar 88 Doppler \[WSR-88D\]) deployed by
the National Weather Service (NWS), Department of Defense, and Federal
Aviation Administration (Fig C-5 in the Appendix). Each radar transmits
the base data (Level II) in near real time to a central site. These data
are subsequently archived at the National Climatic Data Center. In
precipitation or severe weather mode the radars collect volume scans
every 5-6 min.

If a significant TC moves within 215 nm (440 km) of the coast of the
Eastern or Southern United States, then (resources permitting) a P-3
will obtain Doppler radar data to be combined with data from the closest
WSR-88D radars in dual-Doppler analyses. The tail radar is tilted to
point 20 degrees forward and aft from the track during successive sweeps
(the fore-aft scanning technique \[F/AST\]). These analyses could
resolve phenomena with time scales \<10 min, the time spanned by two
WSR-88D volume scans. This time series of dual-Doppler analyses will be
used to describe the storm core wind field and its evolution. The flight
pattern is designed to obtain dual-Doppler analyses at intervals of
10-20 min in the core. The Doppler data will be augmented by deploying
dropwindsondes near the coast, where knowledge of the boundary-layer
structure is crucial for determining what happens to the wind field as a
strong storm moves inland. Dropwindsondes will also be deployed in the
eyewall in different quadrants of the hurricane. To augment the core
analyses, dual-Doppler data can also be collected in the outer portions
of the storm, beyond the range of the WSR-88D, because the alternating
forward and aft scans in F/AST mode intersect at 40 degrees, sufficient
for dual-Doppler synthesis of wind observations.

**Objectives:**

A)  Collect flight-level wind data and make surface wind estimates to
    improve real-time and post-storm surface wind analyses in
    hurricanes.

B)  Collect airborne Doppler radar to combine with WSR-88D radar data in
    post-storm three-dimensional wind analyses.

C)  Document thermodynamic and kinematic changes in the storm during and
    after landfall.

D)  Measure the characteristics of the middle troposphere and the
    hurricane boundary layer with dropwindsondes.

**Mission Description:** This is a *multi-option*, *single-aircraft*
experiment designed to study the changes in TC surface wind structure
near and after landfall. It has several modules that could also be
incorporated into operational surveillance or reconnaissance missions.
It is designed for one or two single-aircraft missions with a P-3 when a
hurricane moves within 215 nm (400 km) of the U.S. coastline. The first
of these 2 flights will typically consist of the real-time module
followed by SFMR and/or Coastal Wind Profile modules. A second flight
could complete the post-landfall module. If the storm either moves
parallel to the coastline or moves slowly inland and resources permit,
it may be repeated with a second flight. While the storm location
relative to the coastline will dictate which combination of these
modules will be flown, the real-time module will generally precede all
of the others.

The aircraft must have working lower fuselage and tail radars. The HRD
workstation should be on board, so radar and GPS dropwindsonde data can
be analyzed and transmitted to NHC. The SFMR should be operated, to
provide estimates of windspeed at the surface. If the AWRAP or C-SCAT is
on the aircraft then it should also be operated to provide another
estimate of the surface windspeeds. If the SRA is working it also should
collect wave and sweep heights to characterize the storm surge and
breaking wavefield near the coast.

If some of the portable Doppler radars (Shared Mobile Atmospheric
Research and Teaching Radar \[SMART-R\] and/or Doppler on Wheels
\[DOW\]), portable profilers and portable wind towers are deployed
between \~65 and 130 km inland in the onshore flow regime as depicted in
Fig. LF_1, this will provide valuable data for the inland decay model.
If possible, one of the DOWs should be positioned relative to the
nearest WSR-88D such that the dual-Doppler lobes cover the largest area
of onshore flow possible. In the schematic shown in Fig. LF_1, one of
the DOWs is positioned north-west of the Melbourne WSR-88D so that one
dual-Doppler lobe is over the coastal waters and the other covers the
inland region. The profiler is positioned in the inland dual-Doppler
lobe to provide independent observations of the boundary layer to anchor
the dual-Doppler analysis.

All modules support real-time and post-storm surface wind analyses. The
flight patterns will depend on the location and strength of the storm
relative to surface observing platforms and coastal radars. The first
two modules could be easily incorporated into a tasked operational
mission. The other three modules are suited to research missions, where
the patterns are not constrained by fix or gale-force wind radii
requirements.

**Real-time module**: The real-time module combines passes over marine
surface platforms with one or more figure-4 patterns in the core of the
hurricane (Fig. LF_1.) The aircraft flies at or below 5,000 ft (1.5 km)
(ideally at 2,500 ft \[750 m\]), so that flight-level windspeeds can be
adjusted to 30 ft (10 m) to combine with measurements from marine
surface platforms. Flight-level and dropwindsonde data obtained near the
platforms will be used to validate the adjustment method. Note that if
the storm is outside of WSR-88D Doppler range then the figure-4 pattern
could be repeated before returning home.

The landfall flight pattern should take advantage of buoys or C-MAN
sites nearby, if those platforms are expected to experience windspeeds
\> 25 ms^-1^. The aircraft descends at the initial point and begins a
low-level figure-4 pattern, possibly modifying the legs to fly over the
buoys (Fig. LF_1). The radar will be in F/AST mode. If time permits the
aircraft would make one more pass through the eye and then fly the
dual-Doppler option. In this example, the pattern would be completed in
about 2.5 h. Dropwindsondes would be deployed near the buoys or C-MAN
sites, and additional dropwindsondes will be deployed at or just inside
the flight-level RMW.

Note that the optimal volume scans for this pattern will be obtained
when the storm is 32-80 nm (60-150 km) from the radar, because beyond 80
nm (150 km) the lowest WSR-88D scan will be above 5,000 ft (1.5 km)
which is too high to resolve the low-level wind field. Within 32 nm (60
km) the volume scan will be incomplete, because the WSR-88D does not
scan above 19.5 degrees. It is essential that these passes be flown as
straight as possible, because turns to fix the eye will degrade the
Doppler radar coverage.

**Coastal Survey module**: When the hurricane is making landfall, this
module will provide information about the boundary layer in the onshore
and offshore flow regimes. Figure LF_2 shows an example for a hurricane
making landfall near Melbourne, Florida. On the first coastal pass the
P-3 would fly parallel 10-15 km offshore to obtain SFMR surface
windspeeds (1-2 in Fig. LF_2). The track should be adjusted so that the
SFMR footprint is out of the surf zone. The second pass should as close
to the coast as safety permits, to sample the boundary layer transitions
at the coast in onshore and offshore flow (3-4 in Fig. LF_2). The first
pass should be at 5,000 ft (1.5 km) or less, and the aircraft could
climb to higher altitudes for the second pass. On both of these passes
the aircraft should fly to 150 km or the radius of gale-force windspeeds
and release dropwindsondes at the RMW and at intervals of 12.5, 25, 50,
75 and 100 or 125 km on either side of the storm track, to sample both
onshore and offshore flow regimes. Finally, to better sample the
adjustment of the off shore flow from land to ocean a short leg would be
flown from the coast spiraling towards the storm center. Three to four
dropwindsondes would be deployed quite near the coast, followed by 3-4
dropwindsondes spaced every 20-30 km along the trajectory. The Doppler
radar will be in F/AST mode, to provide wind estimates on either side of
the aircraft track. This module could be flown when the hurricane is
making landfall or after the storm moves inland. The pattern could be
flown in \~2 h.

**Onshore Wind Profile Evaluation Module:** In this module, the aircraft
will collect vertical profiles of windspeed in various near shore
environments to test the hypothesis that near the coast surface
windspeeds may be lower than the operational flight-level wind reduction
would suggest. Data collected will help evaluate various effects. For
example, roughness lengths may change, especially in higher windspeeds.
The boundary layer changes at the coast; dropwindsonde data will help
indicate whether there are similar changes from open ocean to coastal
waters.

To evaluate the adjustment of windspeeds from normal reconnaissance
altitude to the surface in near-shore conditions, the aircraft should
fly this module at 700 hPa (10000 ft, \~3000 m). The aircraft follows
the flow to the coast (Fig. LF_3), deploying GPS dropwindsondes every
5-10 nm. Then the aircraft turns and flies into the center of the storm,
back off shore, and then upwind to a point to start a new onshore
profile, where each sequence of dropwindsondes is closer to the RMW. The
last sequence could be along the inside edge of the eyewall. To maintain
good SFMR, tail Doppler radar, SRA and AWRAP data collection, the
onshore flow segments should be flown in short straight segments with
quick turns rather than smooth curves.

**Post Landfall Module:** This module is designed to collect kinematic
and thermodynamic data \~1-2 h prior to and up to 6 h after a hurricane
makes landfall. It is essential that ground-based measurements are
obtained in conjunction with those that are being made by aircraft,
since the primary goal is to determine the kinematic and thermodynamic
changes that occur after a hurricane makes landfall throughout the depth
of the lower troposphere.

The P-3 will fly a coastal survey pattern followed by a figure-4 pattern
over land (Fig. LF_4) with \~ 150-km legs at an altitude of \~15,000 ft
(5 km). The P-3 tail radar should be in F/AST mode. These data will aid
in rainfall estimation and will help document the changes in vortex and
rain band structure over land that are crucial to understanding the
environment that supports tornado and mesovortex development.

Over land, available portable wind towers, mesonet stations, profilers
and DOWs should be deployed along the path of the landfalling hurricane
to identify the changes in storm structure as the hurricane moves
inland. The wind towers and mesonet stations will obtain high-resolution
surface wind, temperature, pressure, relative humidity, and perhaps
rainfall measurements. If available, a profiler could be placed at the
center of each line of mesonet stations. The profilers and RASS sounder
will provide wind and temperature measurements within the lowest 3 and 1
km, respectively. Rain gauges should be located at each profiler and DOW
site to obtain high-resolution rainfall measurements, both for
calibrating the radar rainfall algorithms and for documentation of storm
rainfall.

The first set of towers and mesonet stations should be placed as close
as possible to the coastline (\<10 km) to enable accurate documentation
of the surface wind field just after landfall. Other towers or mesonet
stations should be placed \~65 and 135 km inland respectively; however,
these distances will vary depending upon the intensity and speed of
motion of the landfalling storm as well as safety considerations. Fig.
LF_5 shows the estimated time after landfall that is required for the TC
windspeeds to decay to various wind threshold levels as determined using
the Kaplan/DeMaria inland decay model. The spacing between the mesonet
stations located within each group should be \~30 nm (50 km)
perpendicular to the track to maximize the likelihood that one of the
mesonet stations will be located near the RMW of the landfalling storm.

If the inland profilers are mobile, it will be possible to follow severe
weather producing rainbands if safety and logistical considerations
allow. The DOWs should be placed roughly halfway between the two rear
lines of mesonet and profiler stations. The DOWs, in combination with
the profilers with RASS, will aid in documenting the changes in
kinematic and thermodynamic structure of the hurricane after landfall.
An accurate analysis of such changes is crucial to learning more about
the development of mesovortices and/or tornadoes spawned by landfalling
hurricanes. They will also help document the changes in windspeeds
within the PBL of a landfalling hurricane. Finally, the radars will aid
in the measurement of the rainfall associated with the landfalling
hurricane.

**Offshore Intense Convection Module:** As TCs move inland, tornadoes
also become a significant threat to society and one of the most
difficult forecast problems. In 2004 and 2005 alone, over 560 tornadoes
were spawned by 15 TCs impacting the U.S. coastline, resulting in 12
deaths, over 200 injuries, and more than \$100 million in damage. Many
tornadoes are spawned by ***miniature*** ***supercells***. Much of the
forecast challenge is due to significant differences in structure,
organization, and environment from the classic midlatitude supercell:
the miniature supercells are shallower, weaker, shorter-lived, and less
buoyant, but occur in a very moist, high-wind, high-rotation environment
with relatively high vertical wind shear. Furthermore, individual
miniature supercells often occur in close proximity to one another along
organized outer rainbands, whereas their midlatitude counterparts often
occur in relative isolation. As a result, midlatitude conceptual models
have shown very limited success when applied to tornado forecasting in
TCs. Numerous studies have documented the onshore environmental
conditions and evolution of miniature supercells associated with
TC-tornado outbreaks, but little is known about the ***offshore***
***environment and cell evolution*** just prior to tornado outbreaks.
The goal is to document the structure, evolution, and low-level
environment of the stronger convective cells (\>35 dBZ) located offshore
in an outer rainband (\>150 km from the TC center) that will soon move
onshore and potentially spawn tornadoes. This goal is consistent with
the three primary goals of IFEX.

This module focuses on the collection of dual-Doppler radar and vertical
profiles of the lower atmosphere near intense convective cells (\> 35
dBZ on the LF radar) located in an offshore outer rainband (\>150 km
from the storm center) but embedded within the onshore flow. It can be
easily incorporated during either the real-time, coastal survey, or
onshore wind profile module when a qualified outer rainband is
encountered. Figure LF-7 shows an example flight pattern along the
Carolina coast. In order to provide adequate estimates of low-level
vertical shear and instability, the aircraft should fly at an altitude
of 3000 m or higher. The Doppler radar should operate in F/AST mode to
provide wind estimates on each side of the aircraft track. A minimum of
10 dropwindsondes should be deployed. The first flight leg should cross
the target band \~20-25 km downwind of the intense convective cells and
proceed until the aircraft is 25 km outside the rainband axis, deploying
a dropwindsonde at the band axis and end point. The aircraft then turns
upwind and proceeds along a straight track parallel to the rainband
axis, deploying dropwindsondes every 20-25 km. This length of this leg
can adjusted as needed, but should be a minimum of 75 km. When the
aircraft is \~20-25 km upwind of the target cells, the aircraft turns
and proceeds along a track orthogonal to the band axis until the
aircraft is 25 km inside the rainband. Dropwindsondes should be deployed
at the initial and endpoints of this leg as well as at the band axis.
Finally, the aircraft turns downwind and proceeds along a straight path
parallel to the rainband axis, deploying dropwindsondes every 20-25 km.
The end point of this final leg should be \~20-25 km downwind of the
initial target cell to ensure adequate dual-Doppler radar coverage of
all cells. From here other modules can be resumed. The total time to
complete this module should not exceed 60 min, and in most case can be
completed in less time. This flight pattern can be reversed depending
either on the location of the intense cells relative to the initial
approach vector or the need for flight safety. This module could also be
easily incorporate into any tasked operational or research missions in
which an outer rainband (\>150 km from the storm center) with embedded
intense convective cells (\>35 dBZ on the LF radar) is encountered
during ferry to or from the storm core. In other words, this module is
[not]{.underline} strictly limited to the Landfall and Inland Decay
Experiment.

**SFMR Evaluation Module:** This module is similar to the Coastal Survey
module, except that it concentrates on the region with hurricane-force
windspeeds and is designed to collect data to evaluate the performance
of the SFMR in varying ocean conditions near landfall shallow bathymetry
could cause changes to the breaking wave field that would cause changes
in microwave emissions, besides those changes that correlate directly to
windspeed. Fig. LF_5 shows that the aircraft would fly a leg toward the
coast, preferably at 1200 ft above Mean Sea Level (MSL), to gather
high-resolution SRA data to define the wave field. A sequence of
combined AXBT and GPS dropwindsondes will map out the thermodynamic and
boundary layer windspeeds. This leg is followed by a run along the coast
to the maximum offshore flow, where the plane turns and flies offshore,
deploying a further sequence of AXBTs and dropwindsondes. From here the
module could be repeated or the aircraft could execute another module.

In the annual report from the first year of this project and in
subsequent technical reports, higher than expected SFMR windspeed
retrievals have been reported in regions where the water depth is less
than 50 m. Several mechanisms may be the cause of these anomalies, but
the largest is believed to be enhanced wave breaking of both swell and
local sea wave components due to shoaling, i.e. when the water depth
approaches the dominant ocean swell and local sea wavelength (200-300 m
and 50 -- 80 m, respectively). As ocean waves enter shallower water
their height increases as their speed and length decrease. At the point
where the ocean wavelength and depth become approximately equal, the
wave becomes unstable and begins to plunge forward and break. The normal
wave breaking criteria of wave slope (ratio of wave height to wave
length) exceeding 1/7 changes in shallow water and alters frequency of
wave breaking and hence the foam and whitecap coverage that the SFMR
senses. Since this foam is not directly generated by the local wind, but
by a shoaling bottom, and the ocean surface emission is dependent on the
amount of foam, the SFMR retrieval process may over estimate the
windspeed in these conditions. Therefore, the gradient in the water
depth, the direction of the waves, the complexity of the wave field and
other parameters may all affect this process. To begin to understand and
characterize these effects, SFMR observations and in situ ocean surface
wind observations in different water depths, ocean states and wind
conditions are required.

To develop recommended modules that will obtain ocean surface wind
observations collocated with the SFMR observations in water depths
ranging from 50 m to 10 m, and in conditions of onshore and offshore
wind to delineate the effect of long-period ocean swell. Potential wind
observations from ocean wind scatterometry may not suffer from the same
effects, and thus ocean surface backscatter observations collected by
the AWRAP system should also be obtained. If analysis of the AWRAP data
shows no dependence on bathymetry, the AWRAP ocean wind estimates could
be used in future flights to determine the bathymetry effects on the
SFMR wind retrievals. Utilizing AWRAP for this purpose has the advantage
of requiring fewer resources since dropwindsondes would not be needed
and AWRAP would provide continuous wind observations rather than point
observations that are obtained with the dropwindsondes. In addition,
dual aircraft modules are proposed to obtain collocated surface wave
spectra, including swell and local sea components, from the new
Operational SRA (OSRA) which will be mounted on N43RF, a different P-3
from N42RF, where AWRAP is be mounted. Both aircraft will have
operational OC SFMR systems.

The objective of the bathymetry modules is to obtain collocated SFMR and
dropwindsonde estimates of the 10 m windspeed measurements at different
water depths (less than 50 m). In addition to the SFMR, AWRAP and OSRA
observations are desired. Modules for single and dual aircraft need to
be executed for different wind and bathymetry conditions. Ideally the
module(s) should be executed at water depths of 10 m, 20 m, 30 m, 40 m
and 50 m under gale, storm and hurricane-force windspeeds. Each module
is designed to obtain in situ measurements of the 10 m windspeed that
are collocated within approximately 200 hundred meters of the center
point in the SFMR footprint. Because the wind and bathymetry might be
changing spatially and because the SFMR observations are time sequenced
and its beamwidths are finite, each module involves orthogonal cross
patterns over the dropwindsonde splash point. This will allow the
effects of bathymetry on the SFMR to be separated from spatial gradients
in the wind field and bathymetry.

In the case where the wind is onshore or offshore and the bathymetry
does not change by more than a couple of meters per kilometer, an
additional simplified module would simply fly the available aircraft, or
the two P-3 aircraft in tandem, downwind for a flight segment beginning
at the 60-m isobath and continuing to the 10-m isobath while deploying a
sequence of 8 dropwindsondes (from a single aircraft) or 12
dropwindsondes from the two aircraft in tandem. Care would need to be
taken to fly parallel to the surface wind so that the aircraft would fly
over the dropwindsonde splash point. This would be executed at the
onshore and offshore windspeed regimes indicated above.

Figures LF-8 through LF-11 present a proposed flight track pattern for a
single aircraft mission. The AOC SFMR and dropwindsondes are required.
AWRAP is desired but not required. Ocean wave measurements from the OSRA
and/or from buoys are also desired but not required. Wind measurements
from buoys are desirable but not required.

> **TROPICAL CYCLONE LANDFALL WINDFIELDS EXPERIMENT**
>
> ![](media/image19.pct){width="5.4006944444444445in"
> height="6.817361111111111in"}
>
> **Figure LF_1. Real-time module**

-   TAS calibration required. The legs through the eye may be flown
    along any compass heading along a radial from the ground-based
    radar. The **IP** is approximately 100 nm (185 km) from the storm
    center. Downwind legs may be adjusted to pass over buoys.

-   P-3 should fly legs along the WSR-88D radials.

-   Set airborne Doppler radar to F/AST on all legs. Aircraft should
    avoid penetration of intense reflectivity regions (particularly
    those over land).

-   Wind center penetrations are optional

> **TROPICAL CYCLONE LANDFALL WINDFIELDS EXPERIMENT**
>
> ![](media/image20.png){width="6.370138888888889in"
> height="6.938194444444444in"}
>
> **Figure LF_2 Coastal Survey pattern.**

-   First pass starts 150 km from center or at radius of gale-force
    windspeeds, whichever is closer. Pass from **1-2** should be 10-15
    km offshore for optimum SFMR measurements. Release dropwindsondes at
    RMW, and 12.5, 25, 50, 75 and 100 or 125 km from RMW on ether side
    of storm in legs **1-2** and **3-4**. dropwindsondes should be
    deployed quickly at start of leg **5-6**, and then every 10-15 km
    hereafter.

-   Set airborne Doppler to scan in F/AST on all legs, with single PRF
    \> 2400 and 20% tilt. Aircraft should avoid penetration of intense
    reflectivity regions (particularly those over land).

> **TROPICAL CYCLONE LANDFALL WINDFIELDS EXPERIMENT**
>
> ![](media/image21.png){width="6.696527777777778in" height="7.05in"}
>
> Figure LF_3. Coastal Windspeed Profile Evaluation Module.

-   TAS calibration is required. The legs are at 700 hPa (10000 ft,
    3000 m) altitude.

-   Set airborne Doppler radar to F/AST mode at a single PRF 2400 and
    20° tilt on all legs.

-   Aircraft should avoid penetration of intense reflectivity regions
    (particularly those over land).

-   Wind center penetrations are optional.

> **TROPICAL CYCLONE LANDFALL WINDFIELDS EXPERIMENT**
>
> ![](media/image22.pct){width="5.997916666666667in"
> height="6.228472222222222in"}
>
> Figure LF_4. Post landfall module flight pattern.

-   Coastal survey pattern (solid line) at \~10,000-15,000 ft (3-4 km)
    with dropwindsondes near buoys of opportunity and within 10-20 km of
    the shore in both the onshore and offshore flow

-   Inland figure-4 pattern (dashed line) centered on the storm with leg
    lengths of \~80 nm (150 km) at an altitude of \~15,000 ft (5 km).

-   P-3 should fly legs along the WSR-88D radials.

-   Set airborne Doppler radar to F/AST on all legs.

-   Aircraft should avoid penetration of intense reflectivity regions
    (particularly those over land).

-   Wind center penetrations are optional.

> **TROPICAL CYCLONE LANDFALL WINDFIELDS EXPERIMENT**
>
> ![](media/image23.pct){width="6.083333333333333in" height="5.625in"}

Figure LF_5. Maximum sustained surface wind speed after landfall
estimated using the Kaplan/DeMaria (1995) inland decay model for TCs
with landfall intensities of 75, 90,105,120, and 145 kt.

  --------------------- -------------------------------------------------
                        

                        

                        

                        

                        

                        

                        

                        

                        

                        

                        

                        

                        
  --------------------- -------------------------------------------------

##  {#section .unnumbered}

## 

## Table 2. Operational Aerosonde instruments of relevance to boundary layer monitoring.

  -------------- ------------------ -------- -------------- --------------
                                                            

                                                            

                                                            

                                                            

                                                            

                                                            

                                                            

                                                            

                                                            

                                                            
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![](media/image25.png){width="6.8277777777777775in"
height="5.120833333333334in"}

**Figure LF-6. Offshore Intense Convection pattern**.

The **IP** should be a minimum of 150 km from the storm center. The
first leg (**IP-2**) starts 25 km inside the rainband axis. Legs
**IP-2** and **3-4** should be \~20-25 km downwind and upwind of the
target cells to ensure adequate Doppler coverage. Legs **2-3** and
**4-IP** should be 25 km inside and outside the rainband axis. The
length of legs **2-3** and **4-IP** can be adjusted but should be 75 km
at minimum. Deploy dropwindsondes at the start or end points of each
leg, at the band axis crossing points, and at \~20-25 km intervals along
each leg parallel to the band. Aircraft altitude should be at 10,000 ft
(3000 m) or higher. Set airborne Doppler to scan in F/AST mode on all
legs. Aircraft should avoid penetration of intense reflectivity regions
(particularly over land).

> **TROPICAL CYCLONE LANDFALL WINDFIELDS EXPERIMENT**
>
> ![](media/image24.png){width="6.696527777777778in"
> height="6.763888888888889in"}
>
> **Figure LF_7. SFMR Evaluation Module.**

-   Gray area encloses hurricane core with windspeeds \> hurricane
    force.

-   TAS calibration is required. The legs are at 1500-3000 ft
    (500-1000 m) altitude.

-   Set airborne Doppler radar to F/AST mode at a single PRF 2400 and 20
    degree tilt on all legs.

-   Aircraft should avoid penetration of intense reflectivity regions
    (particularly those over land).

Wind center penetrations are optional.

Figure LF-8: Single-aircraft module to collect observations to determine
the impact of bathymetry on SFMR retrievals.

**Notes:**

1.  P-3 enters pattern heading in the direction of increasing or
    decreasing bathymetry gradient. If the gradient is not known, this
    pattern is still recommended as the orthogonal cross pattern will
    allow the determination of whether the bathymetry was changing and
    in which direction.

2.  At time t = 0 s, dropwindsonde 1 is launched. Aircraft maintains a
    level flight.

3.  Dropwindsonde 2 is launched 2 min later (t = 120 s).

4.  Aircraft maintains level flight until the splash location of
    dropwindsonde 1 is determined.

5.  The P-3 executes a series of three 90-degree turns to align for a
    pass over the splash location of dropwindsonde 1. Each turn should
    be sharp (30-degree bank) to minimize turning time and non-level
    flight. Between turns the aircraft should maintain level flight to
    maximize the amount of valid observations collected with the SFMR
    (and AWRAP).

6.  An 8-km level flight leg centered on the dropwindsonde 1 splash
    location is executed. The heading of this leg should be orthogonal
    to the original flight track.

7.  Once the splash location of dropwindsonde 2 is known, the P-3 should
    execute two 90-degree turns (30-degree bank angle) to align for the
    pass over the second splash location. Between turns the aircraft
    should maintain level flight.

8.  An 8-km level flight leg centered on the dropwindsonde 2 splash
    location is executed. The heading of this leg should be orthogonal
    to the original flight track.

9.  The P-3 can exit this module.

This module can be embedded as a sub-module or part of a flight track
dedicated to analyzing bathymetry effects on the SFMR. For the latter,
the aircraft should be heading in the direction of increasing or
decreasing water depth.

Figure LF-9: Single aircraft dedicated bathymetry flight track is shown.
Each submodule (Fig. 1) is executed at water depths of approximately 50
m, 40 m, 30 m, 20 m and 10 m. See notes for Fig. LF-8.

Figure LF-10: Dual aircraft bathymetry module 1.

**Notes for low P-3 (5000 feet):**

1.  P-3 enters pattern heading in the direction of increasing or
    decreasing bathymetry gradient. If the bathymetry gradient is not
    known, this pattern is still recommended as the orthogonal cross
    pattern will allow the determination of whether the bathymetry was
    changing and in which direction.

2.  At time t = 0 s the aircraft executes a 90-degree turn (30-degree
    bank) and then holds level flight. At time t = 90 s, dropwindsonde 1
    is launched.

3.  Dropwindsonde 2 is launched 2 min later (t = 210 s).

4.  P-3 maintains level flight until the splash location of the
    dropwindsonde 1 is determined (\~t = 270 s). The P-3 executes a
    180-degree turn to overfly splash location of dropwindsondes 1
    and 2. Splash location of dropwindsonde 2 is estimated from splash
    location of dropwindsonde 1. Since the release points are separated
    by approximately 12 to 15 km, both dropwindsondes should advect
    similarly.

5.  The P-3 maintains level flight as it overflies the splash locations
    of dropwindsonde 2 and dropwindsonde 1 at approximately t = 390 s
    and t = 510 s, respectively. After flying a minimum of 4 km past the
    splash location of dropwindsonde 1, the P-3 then executes a
    90-degree turn to resume the original flight track exiting this
    module at t = 580 s.

**Notes for high P-3** **(AWRAP, 7000 to 10,000 feet):**

1.  The high altitude P-3 enters the pattern at the same location as the
    low P-3 but delayed by 180 s.

2.  With knowledge of the splash location of dropwindsonde 1, a box
    pattern is executed to overfly the splash locations of
    dropwindsondes 1 and 2. Each leg over each splash location is a
    minimum of 8 km centered on the splash location. The length can be
    extended in order to keep the timing of both P-3s aligned at the
    exit of the flight pattern. During the 8-km legs, the P-3 must
    maintain level flight. In this case the splash location of
    dropwindsonde 2 will already be known and therefore does not need to
    be estimated.

3.  After completing the box pattern, the P-3 executes a 90-degree turn
    to resume the original track with the lower P-3.

Figure LF-11: Alternative dual P-3 bathymetry module.

**Note:**

The high P-3 executes orthogonal cross patterns over each location and
over flies the same track as the low P-3 as it overflies the two splash
locations.

**3. Tropical Cyclone Unmanned Aerial System (UAS) Inflow/Eyewall/Eye
Experiment**

**Program Significance:** While recent composite analyses from Cione et
al. (2000) and Cione and Uhlhorn (2003) have led to new insights
regarding structural details of the hurricane air-sea interface,
sustained and comprehensive observations of the thermodynamic
(temperature and moisture) and kinematic (wind) structure of the
near-surface hurricane environment have never been undertaken. Yet this
environment, where the atmosphere meets the sea, is critically
important:

-   This is where the critical oceanic energy supply is transferred to
    the atmosphere

-   Here, the strongest windspeeds in a hurricane, especially those that
    are most critical for forecasts and warnings, are found

Improved observations in this region will lead to better understanding,
and improved capacity for forecasting TC intensity change. A major
uncertainty in forecasting landfall intensity is the potential for rapid
intensification or decay in the critical 24-h period when major response
decisions have been already made. Enhancing this predictive capability
would save the economy billions of dollars and help reduce the risk of
death and injury for vulnerable populations

Successful utilization of the P-3 and G-IV aircraft have made NOAA a
global leader in the area of hurricane aircraft surveillance and
reconnaissance. However, the danger of near-surface operations in the
extreme hurricane conditions has precluded comprehensive monitoring of
this critical region. Satellites are also unable to monitor this region,
so only scattered local observations from dropwindsondes remain. The
unique low-flying capacity of the Aerosonde UAS platform will address
this significant observational shortcoming. The Aerosonde is capable of
flying at altitudes of 500 feet or less within the high-wind hurricane
eyewall environment. This is thousands of feet lower than any manned
aircraft is able to operate.

The Aerosonde UAS is fully summarized in Holland et al (2000). It has
been undertaking civilian operations since 1995, was the first UAS to
cross the Atlantic Ocean and has an impressive endurance record of over
32 hrs. It has a sophisticated command and control system and the
flexibility to be deployed and commanded from virtually any location.
Initially developed for meteorological and environmental applications in
remote and dangerous conditions, the Aerosonde has been specifically
designed for all-weather operations under

**Table 1. Specifications of Mark 3 Aerosonde UAS.**

  ----------------------- -----------------------------------------------
  **Specifications**      

  Weight, wing span       26-30 lb, 10 ft

  Engine                  24 cc, Fuel Injected engine using unleaded
                          petrol

  Navigation              GPS

  **Operation**           

  Staff for launch and    3 staff: Controller, Engineer,
  recovery                Pilot/Maintenance

  Ground equipment        Proprietary Staging Box, Personal Computer,
                          GPS, Radio Antennae and Iridium Satellite modem

  Flight                  Fully autonomous, under Base Command

  Launch and recovery     Launch from car roof rack, or catapult, land on
                          belly. Able to operate from remote and
                          unprepared surfaces

  Ground and air          UHF or Satcom to Aerosonde, VHF to field staff
  communications          and other aircraft, internet or phone to
                          command center and users.

  **Performance**         

  Speed, climb            Speed 35-80 kt, Climb 3 ms^-1^ at sea level

  Endurance, range        20 to \>30 h, up to 3000 km (depending on
                          payload weight and configuration)
  ----------------------- -----------------------------------------------

Table 2. Aerosonde instruments of relevance to boundary layer
monitoring.

  ----------------- ---------------- ------------------ --------------- -----------------
  **Measurement**   **Instrument**   **Manufacturer**   **Technical**   **Comments**

  T, p, RH          Vaisala RSS901   Vaisala            T\<0.2K,        Standard
                    sensor                              p\<0.555 hPa,   meteorological
                                                        RH\<2% 0.1 Hz   observations
                                                        standard,       
                                                        capable of 1 Hz 

  **V**             Proprietary      AeNA               u, v \< 0.5     Standard
                                                        ms^-1^          meteorological
                                                                        observations

  Sea and land      IR KT11, IR KT15 Heitronics         SST \< 0.5K     Surface ocean and
  surface                                                               land temperature.
  temperature                                                           

  Liquid water      Heymsfield VIPS  NCAR               Video recording Cloud physics and
  content and ice                                       of impacts on   potential spray
  crystal                                               oiled plastic   or salt
  concentration                                                         distributions

  Sea state, ocean  reflectance      NASA               \<10-m          Detailed
  surface                                               resolution.     observations of
  windspeeds, soil                                      Accuracy        surface
  moisture                                              unknown         conditions

  Surface visible   Digital still    Olympus            5 megapixel 3x  High-resolution
  imaging           camera Olympus                      Optical zoom    surface imaging
                    5050                                                

  Surface visible   Sony 555 Video   Sony                               Video of surface
  imaging           camera, fixed                                       conditions
                    mount                                               

  Infrared imaging  Indigo Omega     Indigo Systems     8-12 micron IR  IR surface
                    camera                              imaging         imagery
  ----------------- ---------------- ------------------ --------------- -----------------

harsh conditions and is well suited to the hurricane reconnaissance
role. The aircraft has evolved through to the current Mark 4 version and
its relevant specifications are provided in Table 1. Payloads relative
to hurricane boundary layer missions are listed in Table 2. Aerosonde
command and control is accomplished by UHF command for LOS up to 120 nm,
which may be back to a launch site or can be transferred to a mobile or
other site as required and Iridium SATCOM for OH command to any location
on earth. The required equipment is a lap top computer, a small staging
box (briefcase size) and relevant antennae. AeNA has often operated from
a vehicle and has transferred control to ships and other sites under
operational conditions.

**Mission Description**: The primary objective is to further demonstrate
and utilize the unique capabilities of low latitude long endurance UAS
platforms to better document areas of the TC environment that would
otherwise be either impossible or impractical to observe. In 2008,
operations will be based out of Bridegetown, Barbados. The effort will
include a two-week intensive observing period that will begin sometime
late August or early September. The immediate focus is to document and
significantly improve understanding of the rarely observed TC boundary
layer and undertake detailed comparisons between in-situ and
remote-sensing observations obtained from manned aircraft (P-3 and AFRES
C-130) and satellite-based platforms. In addition, a primary objective
of this effort is to provide real-time, near-surface wind observations
to NHC in direct support of NOAA operational requirements. These unique
data will also be made available to EMC for both data initialization and
forecast verification purposes. The P-3 (flying at 10000 ft)
dropwindsonde and AXBT release points will be regularly spaced (see
notes below). Any mature TC east of Barbados would be considered a
target candidate.

![](media/image30.png){width="4.813194444444444in"
height="4.629861111111111in"}

**Figure 4** TC Inflow/Eyewall/Eye flight tracks for the Aerosonde UAS
and P-3 manned aircraft.

(1) Note 1: UAS take-off and recovery: Bridgetown, Barbados

(2) Note 2: (If possible) conduct pre-IP: UAS-buoy inter-comparisons (T,
    T~d~, p, **V**) at 50-75m latitude

(3) Note 3: UAS IP: 400km from TC center (IP-flight level: 1200m)

(4) Note 4: UAS Descend to 100m. Remain at 100m until 350km. At 350km,
    ascend to 1000m, remain at 1000m until 300km

(5) Note 5: UAS Descend to 100m, remain at 150m until 250km. At 250km,
    ascend to 1000m, remain at 700m until 200km.

(6) Note 6: **When the UAS is \~200km from the TC center, begin P-3
    figure-4 Pattern.**

(7) Note 7: P-3 will fly at 10000 ft and release co-located AXBT and
    dropwindsonde pairs every 100 km between 300-100km from the center
    (and every 50km from 0-100km from the TC center). For
    non-penetration legs, an additional AXBT or dropwindsonde will be
    launched at the leg mid-point.

(8) Note 8: **After completing the figure-4 pattern, the P-3 will begin
    pattern beta at 10000 ft and repeating the identical dropwindsonde
    pattern conducted during the figure-4 pattern. A total of 38 AXBT
    and dropwindsondes are required for this mission.**

(9) Note 9: Post storm-comparisons with P-3 Doppler radar wind
    observations and SFMR are desired so both instruments will need to
    be fully functional.

(10) Note 10: At 250km, UAS ascend to 700m, remain at 700m until 200km.
     From 200-100km, continuous 1000m-100m soundings

(11) Note 11: At 100km, UAS ascend to200m for eyewall penetration
     (\~40-50km from center). In eye, UAS conducts 5-15km radius
     corkscrew eye sounding to 3000m

(12) Note 12: UAS begins final eyewall penetration at 3000m altitude
     (1000m if manned aircraft present)

(13) Note 13: **IF AFRES C-130 PRESENT NO EYE SOUNDINGS WILL BE
     CONDUCTED**

(14) Note 14: **RETURN TO AEROSONDE BASE OF OPERATIONS**

**ifex missions (CONTinueD)**

**4. Tropical Cyclogenesis Experiment**

**[Motivation]{.underline}**

While forecasts of TC track have shown significant improvements in
recent years (Aberson 2001), corresponding improvements in forecasts of
TC intensity have been much slower (DeMaria and Gross 2003). The lack of
improvement in intensity forecasting is the result of deficiencies in
the numerical models (e.g., resolution limitation and parameterization
inadequacies), deficiencies in the observations, and deficiencies in
basic understanding of the physical processes involved. The problem
becomes even more acute for forecasting tropical cyclogenesis. While
global models have shown some skill in recent years in predicting
tropical cyclogenesis, understanding of the physical processes involved
remains limited, largely because observing genesis events is a difficult
task. However, a key aspect of IFEX (Rogers et al. 2006) is the
collection of observations during all portions of a TC lifecycle,
particularly on the early lifecycle stages. This emphasis on the early
stages of the lifecycle will provide an opportunity to observe several
genesis events and improve understanding of this key process, leading to
better predictions of tropical cyclogenesis, organization, and
intensification.

Since both tropical cyclogenesis and TC intensity change can be defined
by changes in low- and mid-level vorticity, knowledge of the processes
that play a significant role in genesis will also advance understanding
of intensity change. A better understanding of the processes that lead
to an increase in low- and mid-level cyclonic vorticity will also allow
NHC to better monitor and forecast tropical cyclogenesis and intensity
change, improvements that would be especially valuable for those events
that threaten coastal areas. Data obtained by aircraft investigating
potential genesis events will positively impact operations and research
in other ways as well. The collection of three-dimensional data at all
stages in a TC lifecycle is one of the key requirements for NCEP as a
part of IFEX. Such data will provide information that will guide the
development of balance assumptions and error covariance matrices
important in the development of data assimilation schemes for models
(i.e., HWRF) that will be used in these environments. They will also
provide important datasets for evaluating the performance of HWRF. In
addition to improving the understanding and forecasting of tropical
cyclogenesis and intensity change, the proposed experiment will yield
useful insight into the structure, growth and ultimately the
predictability of the systems responsible for almost all of the
weather-related destruction in the tropical Atlantic and East Pacific.
Investigation of systems that fail to complete the genesis process will
also result in a better understanding and prediction of easterly
disturbances in general so that distinction can be better made between
developing and non-developing tropical disturbances.

**[Background]{.underline}**

Tropical cyclogenesis can be viewed as a rapid increase of low-level
cyclonic vorticity organized on the mesoscale within a region of
enhanced convective activity. Numerous hypotheses have been advanced in
the literature to explain how this vorticity develops and amplifies. One
of the key aspects differentiating these hypotheses centers on whether
the lower-tropospheric cyclonic vorticity begins in the mid-levels and
develops downward to the surface or begins in the lower troposphere and
builds upward to the middle troposphere -- the so-called top-down vs.
bottom-up mechanisms. Prominent top-down theories include one study
which showed observations of multiple midlevel vortices prior to genesis
in the West Pacific (Ritchie et al. 1997) that led them to view the
genesis process as a stochastic one whereby chance merger and
axisymmetrization of these midlevel vortices leads to growth of the
circulation to the surface by increasing the Rossby-Prandtl-Burger
penetration depth of potential vorticity anomalies associated with the
vortices. Another study supporting the top-down approach showed
observations of genesis in the East Pacific (Bister and Emanuel 1997)
and hypothesized that downdrafts driven by evaporational cooling
advected the vorticity of the midlevel vortex downward, enhancing
convection and low-level vorticity production.

The set of hypotheses supporting the bottom-up approach generally
describes the genesis process as being driven by low-level convergence
that increases cyclonic vorticity near the surface through vortex
stretching. One such bottom-up hypothesis emphasizes the role of a
parent midlevel vortex in axisymmetrizing nearby low-level convectively
generated cyclonic vorticity, called vortical hot towers, that leads to
the spin-up of the surface circulation (e.g., Montgomery and Enagonio
1998; Davis and Bosart 2001; Montgomery et al 2004). A similar
hypothesis was advanced by Rogers and Fritsch (2001) and Chen and Frank
(1993) who emphasized the role of the midlevel vortex and high midlevel
humidity in providing a favorably reduced local Rossby radius of
deformation to retain the heating from convective bursts and spin up
low-level vorticity through low-level stretching caused by the
convective heating. Another set of theories focuses on the reduction of
the lower tropospheric effective static stability to low values in the
core of incipient cyclones. Suppression of convectively induced
downdrafts is one means of accomplishing this (Emanuel 1995; Raymond,
Lopez, and Lopez 1998). Eliminating low-level outflows produced by the
downdrafts allows the inflow of updraft air to spin up the low-level
circulation, leading to the development of the warm-core characteristic
of the TC.

**[Objectives]{.underline}**

With the above background in mind, the objectives are defined as
follows:

1.  [Test prevailing hypotheses relating to top-down vs. bottom-up
    development]{.underline}

This objective will be addressed by documenting the development of
low-level vorticity in the presence of a midlevel vortex center, and
vice versa. It will also be addressed by documenting the interactions
between low- and mid-level vortices in pre-genesis environments.

2.  [Document aspects of mesoscale and synoptic-scale environment of
    incipient disturbances to identify characteristics necessary in
    genesis]{.underline}

Key tasks in addressing this objective involve assessing the importance
of pre-existing vorticity and broad areas of high humidity and
determining the importance of their spatial and temporal distribution in
tropical cyclogenesis. Another important question to address is the
role, if any, that a midlevel vortex plays in governing the distribution
and magnitude of deep convection, and to determine the importance of
downdraft suppression in limiting boundary layer stabilization. A final
task is to examine hypotheses relating humidity and static stability
profiles to downdraft morphology and the vortex response to convective
heating.

**[Links to IFEX]{.underline}**

It supports the following NOAA IFEX goals:

-   **Goal 1**: Collect observations that span the TC lifecycle in a
    variety of environments;

-   **Goal 3**: Improve understanding of the physical processes
    important in intensity change for a TC at all stages of its
    lifecycle;

**[Experiment Description]{.underline}**

The physical processes that are important in tropical cyclogenesis span
a wide spectrum of temporal and spatial scales, with time scales ranging
from minutes to days and space scales ranging from mm to hundreds of km.
Furthermore, many of the processes are highly nonlinear and transient.
For these reasons, an experimental approach that combines observations
and numerical modeling is required to adequately address the questions
posed above. When possible, GenEx missions will be coordinated with
SALEX. This coordination will involve the P-3 and/or G-IV and be
executed on a case-by-case basis.

***Observational component***

Recent observations from airborne Doppler radar have identified
important processes on the mesoscale that contribute to tropical
cyclogenesis. For example, results obtained from a P-3 aircraft
investigation of Dolly in 1996 (Reasor et al. 2005) indicate its genesis
was strongly influenced by persistent, deep convection in the form of
mesoscale convective systems (MCSs) that developed in association with
an easterly wave over the Caribbean. Within this deep convection an
eye-like feature formed, after which time the system was declared a
depression. The initial development of the low-level circulation in both
Dolly (1996) and Guillermo (1991) occurred in the presence of multiple
midlevel vortices. The close proximity of the low- and mid-level
vorticity maxima (often within 50-100 km horizontally) observed in these
two genesis cases supports a further examination of the aforementioned
vortex merger ideas. To adequately diagnose the role of these vortices,
it is vital that they be sampled in their entirety (which will
invariably depend on the distribution of precipitation scatterers) and
with a temporal resolution that allows time continuity of the vortices
to be established when possible.

In addition to the wind and rainfall measurements provided by the
Doppler radars, measurements of temperature and moisture are vital to
address the thermodynamic issues described above. Dropwindsondes
released in a regular grid will enable the determination of
thermodynamic fields in the vicinity of the incipient system, as well as
enable the calculation of mean divergence and vorticity fields around
the system, important in determining the strength and depth of the
downdrafts (provided time aliasing is minimized). The dropwindsondes
should be released from as high an altitude as possible to provide
observations of mid-level humidity and windspeeds where scatterers are
not present. The tail radars on the P-3s will also enable a
determination of the presence of saturation when scatterers are
observed.

This may be executed with the P-3 alone, but optimally it will involve
the participation of the NOAA G-IV aircraft as well. Flights will occur
into incipient tropical disturbances over the western Caribbean Sea,
Gulf of Mexico, and tropical Atlantic Ocean. For these missions the P-3
will be based primarily in Barbados, though operations can also occur
from St. Croix and Tampa. The systems flown here will primarily be
incipient systems.

The primary mission will require the P-3 flying back-to-back missions.
It will fly mesoscale survey patterns designed to document any suspected
low- and mid-level vortices and sample any changes in the low- and
mid-level thermodynamic fields associated with the incipient systems.
Crucial to a complete understanding of the genesis process is the
collection of observations with high temporal and spatial resolution.
Therefore, the staggered P-3 missions are designed to commence on
station at midnight (12 AM) local and again on station at noon (12 PM)
local. If it is not possible to fly the P-3 at 12-h staggering, then
24-h staggering will be performed. If available, the G-IV aircraft would
fly simultaneously at upper levels (42,000 ft or 175 hPa) and collect
observations to a distance of \~1500 km from the center of the
disturbance. This G-IV mission would only occur if operations happened
in the tropical Atlantic or Western Caribbean and there were indications
of mid- or low-level dry air in the vicinity of the disturbance.

The main aircraft for the mesoscale flights will be the P-3. Doppler
radar observations, dropwindsondes, and flight-level observations
obtained during these flights will help locate low- and mid-level
vortices and help document their structures and life cycles. Primary
aspects will be to observe the complete life cycle and interaction of
low- and mid-level vortices, understand how these vortices are
influenced by the diurnal cycle of convection, and observe the evolution
of the thermodynamic fields as the incipient system evolves. The
location of persistent areas of deep convection and candidate vortices
will be determined using high-resolution visible and infrared GOES-winds
produced available online, supplemented by NASA TRMM imagery when
available. Additionally, favorable environments for deep convection and
vortex development, such as those described in the Introduction, will be
identified using water vapor loops, model analysis fields enhanced by
satellite wind measurements, and QuikSCAT imagery, also available
online.

Staggered missions with the P-3 aircraft will begin with the aircraft
flying one of two survey patterns at 14,000 ft (4 km). The primary
purpose of these patterns will be to collect F/AST Doppler radar and
dropwindsonde data in the area of deep convection in order to map the
evolution of the three-dimensional wind and thermodynamic structure of
the deep convection and incipient vortex. Two possible patterns can be
flown, with the decision of which pattern determined by the degree of
organization of the system. For incipient systems that are relatively
disorganized, a sawtooth pattern is flown (Fig. 1) along the axis of an
easterly wave. Leg lengths will be 150-200 nm (250-300 km), with some
variability dependent on the size of the system and the time available
on station. The pattern will be centered approximately on any
discernible circulation, if identifiable, or on a dominant area of
convective activity. After the circulation center or convective area is
passed, the sawtooth pattern is mirrored and the aircraft completes a
return trip, creating a series of diamond shapes to complete the
pattern. This return trip will provide some greater temporal continuity
to the observations.

As a system becomes better organized, a second survey pattern is flown
(Fig. 2), consisting of a square-spiral centered on a broad low- or
mid-level circulation center. If multiple mesoscale convective systems
exist embedded within a parent circulation, the pattern will be centered
on the parent circulation. Dropwindsondes are released at regular
intervals to create a near uniform grid covering the circulation and
including any MCSs, if possible. The spacing between the outer spiral
and the inner box pattern is nominally set for 60 nm (111 km), but it
can be varied to ensure optimal representation of the convective and
mesoscale features.

Once a persistent low-level vortex is identified, subsequent missions
will include a rotating figure-4 pattern (Fig. 3) centered on the
vortex. Flight legs will be 60-120 nm (111-225 km) to allow for the
collection of data with high temporal and spatial resolution in the
vicinity of the vortex center. The length of these flight legs is
designed to completely include the low-level vortex and convection
associated with it. Depending on the leg lengths and the time available
on station, the pattern may consist of higher azimuthal resolution. The
tail radar will operate in F/AST mode during the entirety of these
patterns. For the P-3 using the NOAA antenna, the tail radar will
operate in continuous mode during the Microphysics Module.

If available, the G-IV will fly a synoptic pattern at maximum altitude
to observe the troposphere with dropwindsondes in the pre-genesis and
incipient tropical disturbance environment. The most likely scenario
calls for the G-IV to fly a SALEX pattern as the system is interacting
with a SAL (Fig. 4).

The possible availability of multiple aircraft leads to several
different scenarios. A summary of the potential combinations of aircraft
during genesis follows:

**Option 1 (Optimal experiment):**

The optimal experiment is when the P-3 aircraft will fly in the tropical
Atlantic, Gulf of Mexico, or western Caribbean basins, either diamond or
square-spiral survey patterns to locate low- and mid-level vortices
(Figs. 1 or 2). These flights will be flown in coordination with the
G-IV aircraft, providing synoptic-scale measurements of upper- and
lower-tropospheric observations around the incipient disturbance. Once a
persistent mid-level vortex is located, the P-3 will fly either rotating
figure-4 (Fig. 3) or square-spiral patterns. The lesser experiment is
only with the P-3.

**Convective Burst Module:**

This is stand-alone module that is one hour or less in. Execution is
dependent on system attributes, aircraft fuel and weight restrictions,
and proximity to operations base. The objectives are to obtain
quantitative description of the kinematic, thermodynamic, and electrical
properties of intense convective systems (bursts) and the nearby
environment to examine their role in the cyclogenesis process. It can be
flown separately within a mission designed to study local areas of
convection or at the end of one of the survey patterns. Once a local
area of intense convection is identified, the P-3 will transit at
altitude (14,000 ft.) to the nearest point just outside of the
convective cores and fly a circumnavigation of the convective area. The
circumnavigation will consist of a series of straight legs just outside
of the main convection. The tail radar should be operated in F/AST
sector scan and regularly spaced dropwindsondes (10-20 km apart) will be
released during this time. Once the circumnavigation is completed, and
the P-3 is near the original IP, two straight-line crossings of the
convective area should be performed with the P-3 avoiding the strongest
cores, as necessary for safety considerations. The P-3 can fly at either
at a constant radar altitude of 14,000 ft. or, if conditions warrant, to
perform a slanted ascent through the melting layer on the first pass and
a slanted descent on the return pass. If time permits, the P-3 should
descend to the lowest safe altitude and perform another circumnavigation
(or partial one) of the convective burst. No dropwindsondes will be
released during the low-level run.

**Tropical Cyclogenesis Experiment**

![](media/image31.png){width="6.270138888888889in"
height="5.770138888888889in"}

Figure 1: P-3 Pre-genesis early organization vortex survey pattern --
Diamond pattern

-   Note 1: TAS calibration is required.

-   Note 2. The pattern is flown with respect to the wave axis,
    typically inclined at 30-40° from N, or relative to circulation or
    vorticity centers.

-   Note 3. Length of pattern (axis parallel to wave axis) should cover
    both low- and mid-level vortices, leg lengths range from 150 -- 200
    nm (275-375 km).

-   Note 4. Fly 1-2-3-4-5-6-7-8 at 14,000 ft (4 km) altitude, deploying
    dropwindsondes at all locations denoted by black circles.

-   Note 5. Set airborne Doppler radar to scan F/AST on all legs.

**Tropical Cyclogenesis Experiment**

![](media/image32.png){width="5.925in" height="5.843055555555556in"}

Figure 2: P-3 Pre-genesis late organization vortex survey pattern --
Square-spiral pattern

-   Note 1. TAS calibration is required.

-   Note 2. The pattern is flown with respect to the wave axis,
    typically inclined at 30-40° from N, or relative to circulation or
    vorticity centers.

-   Note 3. Release dropwindsondes at all numbered points. Releases at
    intermediate points can be omitted if dropwindsonde supply is
    insufficient.

-   Note 4. The spacing between the outer spiral and inner box
    (nominally set to 60 nm (111 km)) can be increased or decreased
    depending on the size of the disturbance.

-   Note 5. Fly 1-2-3-4-5-6-7-8-9-10-11-12 at 14,000 ft (4.0 km)
    altitude.

-   Note 6. Set airborne Doppler radar to scan F/AST on all legs.

-   

-   Tropical Cyclogenesis Experiment

![](media/image33.png){width="6.353472222222222in"
height="6.020138888888889in"}

Figure 3: P-3 Post-genesis rotating figure-4 pattern

-   Note 1: TAS calibration is required.

-   Note 2. The pattern may be entered along any compass heading.

-   Note 3. Fly 1-2-3-4-5-6-7-8 at 14,000 ft altitude, 60-120 nm
    (111-225 km) leg length.

-   Note 4 Set airborne Doppler radar to scan F/AST on all legs.

**Tropical Cyclogenesis Experiment**

![](media/image35.jpeg){width="6.313194444444444in" height="7.3in"}

Figure 4: Convective Burst module

-   
-   
-   
-   
-   
-   
-   

**IFEX Missions** **(Continued)**

**5.** **Nadir Off-set** **[SFMR]{.smallcaps}**
**[Experiment]{.smallcaps}**

1\. Rationale

The HIRad is currently under development by NASA and NOAA and is
intended to follow the SFMR and extend its spatial coverage by providing
a wide swath measurement. It is intended to be the next-generation
scanning SFMR intended to reduce surface wind uncertainty by extending
the SFMR measurement swath in the cross --track direction. In order to
design HIRad and to retrieve windspeed and rain rate over its full
swath, an ocean surface emissivity model is required that covers
windspeeds over the full SFMR range of greater than 70 ms-1and over the
full HIRad swath of approximately ± 60-degree incidence angle. Existing
models cover high windspeeds at nadir only (SFMR) and cover large
incidence angles only during turns at less than hurricane force.
Therefore, a new surface emissivity model is being developed under the
HIRad project to meet future needs in radiative transfer analyses.

The HIRad surface emissivity model is being developed using SFMR
algorithms for nadir incidence and using SFMR brightness temperature
measurements in aircraft banks and turns for off-nadir modeling.
Aircraft turns in past hurricane flights have typically produced maximum
bank angles of 30 -- 35 degrees or less. Therefore, there is a critical
need for brightness temperature data in hurricane-force windspeeds at
incidence angles greater than 35 degrees in order to complete the HIRad
surface emissivity model. The Nadir Off-Set SFMR Experiment is intended
to fill this need. A further rationale is to provide off-nadir SFMR
measurements to Remote Sensing Solutions to develop an SFMR SST
algorithm using off-nadir SFMR observations with the objective of
leveraging crucial flight resources.

2\. Flight Pattern Description

A full pattern consists of three complete circles. It is important
throughout this pattern for the rolls to be accomplished during the
turns to be at constant pitch insofar as possible. Changes in pitch will
translate to changes in SFMR polarization. For a given hurricane,
straight and level passes through the eyewall region will provide the
highest windspeeds at approximately 45-degree incidence, and circle
maneuvers just outside the eyewall at various bank angles would provide
data at the highest incidence angles and highest possible windspeeds.

When executing these rolls it is important to perform an upwind turn in
order to maintain station-keeping in high windspeeds. These patterns are
to be flown when situation and time dictate. Over the course of a
season, it is anticipated that a series of inbound and outbound circle
flights could be obtained at approximately 4 separate windspeed ranges:
20-25 ms-1, 30-35 ms-1, 40-45 ms-1 and 50-55 ms-1. It is likely that
data may need to be stratified also by storm quadrant relative to storm
motion, a goal that may prove difficult in one season. A dropwindsonde
should be released either at the beginning or end of the pattern.

> **6. Tropical Cyclone/AEW Arc Cloud** **Experiment**

**Program Significance:** Arc clouds are common features in mid-latitude
thunderstorms and MCSs. They denote the presence of a density current
that forms when dry middle-level (\~600-800 hPa) air has interacted with
precipitation. The convectively driven downdrafts that result reach the
surface or near-surface and spread out from the convective core of the
thunderstorm. The mid-level moisture found in the *moist tropical* North
Atlantic sounding described by Dunion (2008) is hypothesized to be
insufficiently dry to generate extensive arc clouds around an AEW or TC.
However, substantial (100s of km in length and lasting for several
hours) arc clouds consistently form in the tropics in the periphery of
these tropical disturbances. Dunion (2008) did described two addition
types of air masses that are frequently found in the tropical North
Atlantic and Caribbean that could effectively initiate the formation of
large arc clouds: the *SAL* and *mid-latitude dry air intrusions*. Both
of these air masses were found to contain substantially dry air (\~50%
less moisture than the *moist tropical* North Atlantic sounding) in the
middle levels of the atmosphere and can affect the tropical North
Atlantic and Caribbean throughout the summer months.

It is hypothesized that these arc cloud features can significantly
impact an AEW or TC (particularly smaller, less developed systems) via
two mechanisms:

1.  As the arc clouds race away from the convective core region, they
    create low-level outflow in the quadrant or semicircle of the AEW or
    TC in which they form. This outflow pattern counters the typical
    low-level inflow that is vital for TC formation and maintenance;

2.  Arc clouds are formed when cool, dry air generated by convectively
    driven downdrafts rapidly sinks to the surface or near-surface and
    races away from the AEW/TC convective region. This combination of
    downdrafts and cool, dry air help stabilize the middle to lower
    troposphere and may even act to stabilize the boundary layer.

**Objective:** The main objective of the TC/AEW Arc Cloud Experiment is
to:

-   Collect flight-level and dropwindsonde observations across arc cloud
    features in the periphery of an AEW or TC to improve understanding
    of how these features may limit short-term intensification.

**Links to IFEX:** This experiment supports the following NOAA IFEX
goals:

-   **Goal 3**: Improve understanding of the physical processes
    important in intensity change for a TC at all stages of its
    lifecycle.

**Mission Description:** This experiment is designed to utilize the P-3
\[flight level (preferably flying at ≥5000 ft) and dropwindsonde data\]
or G-IV (dropwindsonde data) aircraft. It can be included within any of
the following missions: SALEX, Aerosonde Experiment, or TC Landfall and
Inland Decay Experiment or as part of operational G-IV Synoptic
Surveillance and NHC-EMC-HRD Three-dimensional Doppler Winds Experiment
missions. Total precipitable water satellite imagery will be used to
identify mid-level dry air (≤45 mm) in the periphery of the AEW or TC.
These targeted areas of dry air will be regions of favored arc cloud
formation and should be monitored closely using satellite imagery
(preferably 1 km visible) during the mission. Once an arc cloud feature
has been identified, a dropwindsonde sequence (preferably running
perpendicular to the arc cloud) will be made between the convective area
where the arc cloud originated to at least 20 km beyond the leading edge
of the arc cloud. Special attention should be paid to the transition
zone across the leading edge of the arc cloud and to the environment
adjacent to the convective core area where the arc cloud originated
(behind the arc cloud). Dropwindsonde spacing will be \~20 nm \[reduced
to \~10 nm spacing closer (≤20 nm) to the arc cloud\], and the transect
can be made inbound (sampling in front of, across, and then behind the
arc cloud) or outbound (sampling behind, across, and then ahead of the
arc cloud) relative to the convective core region of the AEW or TC. In
addition to the more common arc cloud that propagates away from the AEW
or TC, a second arc cloud has occasionally been observed propagating in
toward the AEW or TC. This second arc cloud appears to spawn from the
same convective region as the outbound arc cloud and simply moves toward
the AEW or TC instead of away from it. If a second inward propagating
arc cloud is identified, the dropwindsonde sequence should be extended
to span the environments ahead of (relative to arc cloud motion) both
arc clouds.

![](media/image36.pct){width="3.0in" height="3.0in"}
![](media/image37.pct){width="3.0in" height="3.0in"}

> **Figure ARC-1:** GOES visible satellite imagery showing arc clouds
> racing away from the convective core regions of (left) 2003 Hurricane
> Isabel and (right) 2007 Pre-Tropical Depression Felix.

**\
**![](media/image38.pct){width="3.522222222222222in"
height="3.504166666666667in"}

> **Figure ARC-2:** The P-3 or G-IV flight track inbound or outbound to
> or from the TC or AEW. Azimuth and length of dropwindsonde sequences
> during G-IV Synoptic Surveillance missions will be dictated by the
> pre-determined flight plan. For these cases, any G-IV flight legs that
> transect through the trailing and leading edges of the arc cloud are
> candidates. When multiple arc clouds are present, the feature that is
> closest to the pre-determined flight track is desirable.

![](media/image39.pct){width="3.5597222222222222in"
height="3.504166666666667in"}

> **Figure ARC-3:** The P-3 or G-IV flight track inbound to, or outbound
> from, the TC or AEW. Azimuth and length of dropwindsonde sequences
> during G-IV Synoptic Surveillance missions will be dictated by the
> pre-determined flight plan. For these cases, any G-IV flight legs that
> transect through the trailing and leading edges o the arc cloud are
> candidate.

![](media/image40.pct){width="3.517361111111111in" height="3.5in"}

**Figure ARC-4:** The Aerosonde flight track (blue curve) inbound to the
TC or AEW. Azimuth and length of the Aerosonde flight leg ahead of,
across, and behind the arc cloud will be dictated by position of the
Aerosonde spiraling track relative to the arc cloud feature. For these
cases, any Aerosonde flight legs that transect through the trailing and
leading edges of the arc cloud are candidates.

**ifex missions (continued)**

**7. Saharan Air Layer Experiment (SALEX)**

#  

**INTRODUCTION**

**Saharan Air Layer Experiment:** This is a multi-option, multi-aircraft
experiment which uses dropwindsondes launched from the NOAA G-IV (flying
at \~175-200 hPa or \~45,000-41,000 ft) and NOAA P-3 (flying at
\~500-700 hPa or 18,000-10,000 ft) to examine the thermodynamic and
kinematic structure of the SAL and its potential impact on TC genesis
and intensity change. The dropwindsonde release points will be selected
using real-time GOES SAL tracking imagery from the University of
Wisconsin-Cooperative Institute for Meteorological Satellite Studies
(UW-CIMSS) and mosaics of Special Sensor Microwave Imager (SSM/I) total
precipitable water from the Naval Research Laboratory. Specific effort
will be made to gather atmospheric information within the SAL as well as
regions of high moisture gradients across its boundaries and the region
of its embedded mid-level easterly jet. The goals are to better
understand and predict how the SAL dry air, mid-level easterly jet, and
suspended mineral dust affect Atlantic TC intensity change and to assess
how well these components of the SAL are being represented in forecast
models.

**Program Significance:** The Saharan SAL has been investigated fairly
extensively during the past several decades, buts its role in
influencing Atlantic TCs has not been thoroughly examined. The SAL is
characterized by a well-mixed layer that originates over the arid
regions of the Sahara and often extends up to \~500 hPa (\~18,000 ft)
over the African continent. This air mass is extremely warm and dry,
with temperatures that are markedly warmer (\~0.5-5.0^o^C in the western
North Atlantic and \~5-10^o^C in the eastern North Atlantic) than a
typical tropical sounding. Additionally, the relative humidity (mixing
ratio) in the SAL is \~30-35% (\~3 g kg^-1^) drier than a typical moist
tropical sounding. The SAL is often associated with a mid-level easterly
jet centered at about 700 hPa (\~10,000 ft) and concentrated along its
southern boundary.

SAL outbreaks typically move westward off the western coast of North
Africa every 3-5 days during the summer months. There are several
characteristics of these frequent outbreaks that can act to suppress
Atlantic TC formation:

1)  The SAL contains **dry, stable air** that can diminish local
    convection by promoting convectively driven downdrafts in the TC
    environment.

2)  The SAL contains a **mid-level easterly jet** that can significantly
    increase the local vertical wind shear. The low-level circulations
    of TCs under the influence of this jet tend to race out ahead of
    their mid and upper-level convection, decoupling the storm and
    weakening it.

3)  **Mineral dust** suspended within the SAL absorbs solar energy and
    subsequently releases longwave infrared energy. These thermal
    emissions act to warm the SAL and can re-enforce the tropical
    inversion that already exists in the tropical North Atlantic. This
    warming helps to stabilize the environment and also limits vertical
    mixing through the SAL, allowing it to maintain its distinctive low
    humidity for extended periods of time (several days) and over long
    distances (1000s of km)

**Objectives:** The main objectives of SALEX are to:

-   Better understand how the SAL dry air, mid-level easterly jet, and
    suspended mineral dust affect Atlantic TC intensity change.

-   Include the moisture information from the dropwindsondes in
    operational parallel runs of the NOAA Global Forecast System (GFS).
    The impact of these data on the GFS (and HWRF) initial and forecast
    humidity fields and its forecasts of TC track and intensity will be
    assessed.

**Links to IFEX:** This experiment supports the following NOAA IFEX
goals:

-   **Goal 1**: Collect observations that span the TC lifecycle in a
    variety of environments;

-   **Goal 3**: Improve understanding of the physical processes
    important in intensity change for a TC at all stages of its
    lifecycle.

**Mission Description:** The NOAA G-IV (flying at \~175-200 hPa or
\~45,000-41,000 ft) and NOAA P-3 (flying at \~500-700 hPa or
\~18,000-10,000 ft) dropwindsonde release points will be based on a
flight pattern selected using information from the UW-CIMSS/HRD GOES SAL
tracking product and mosaics of SSM/I TPW from NRL Monterey. Specific
effort will be made to gather atmospheric information within the SAL,
the transitional environment (regions with high gradients of humidity)
across its boundaries, its embedded mid-level easterly jet, and the
immediate surrounding moist tropical environment. When possible, SALEX
missions will be coordinated with the Tropical Cyclone Genesis
Experiment (GenEx). This coordination will involve the P-3 and/or G-IV
and be executed on a case-by-case basis. Several SAL/TC interaction
scenarios are candidates for SALEX missions:

**[Option 1:]{.underline}** Single TC located along the southern edge of
the SAL (Fig. 1). Depending on the proximity of these two features, the
SAL dry air may be wrapping into the TC low-level circulation (western
semicircle).

*[G-IV:]{.underline}* The G-IV **IP** will be in the NW quadrant of the
TC (preferably west of the SAL leading edge) and the initial portion of
the 1^st^ leg (**IP-2**) will focus a dropwindsonde sequence across the
high gradient region of humidity at the SAL leading edge. There will be
intermittent dropwindsondes along the remainder of the first leg
(**IP-2**), with higher density sequences along pre-determined regions
of interest (e.g. dry SAL air). The 2^nd^ leg (**2-3**) will focus a
dropwindsonde sequence across the SAL southern boundary to capture
gradients of humidity and wind shear (associated with the SAL mid-level
easterly jet). Subsequent intermittent releases will be made along this
leg (**2-3**) to sample the ambient moist tropical environment. The
3^rd^ leg (**3-4**) will include a dropwindsonde sequence that will be
focused along the dry air inflow region on the west semicircle of the
TC. This dropwindsonde sequence will focus on sampling the intrusion of
low humidity SAL air into the TC circulation and how the SAL vertical
structure and moisture content modify as it advects closer to the TC
core. The SAL leading edge (rooster tail) will be sampled by a
dropwindsonde sequence during the final leg (**4-FP**).

*[P-3:]{.underline}* The P-3 **IP** will be in the SW quadrant of the TC
and the initial portion of the 1^st^ leg (**IP-2**) will focus on
sampling the ambient moist tropical environment south of the TC. The
2^nd^ leg (**2-3**) will include sampling the ambient moist tropical
environment east of the TC as well as focusing a dropwindsonde sequence
across the SAL southern boundary to capture gradients of humidity and
wind shear (associated with the SAL mid-level easterly jet). The 3^rd^
leg (**3-4**) will include a dropwindsonde sequence that will be focused
along the dry air inflow region on the west semicircle of the TC. This
dropwindsonde sequence will focus on sampling the intrusion of low
humidity SAL air into the TC circulation and how the SAL vertical
structure and moisture content modify as it advects closer to the TC
core. The final leg (**4-FP**) will include a penetration of the TC
center of circulation followed by dropwindsonde sequences targeting the
SAL west of the TC. The final dropwindsonde sequence will sample the SAL
leading edge (rooster tail) west of the TC.

**[Option 2]{.underline}**: Single TC is embedded within the SAL and
intensifies upon emerging. These systems are often candidates for rapid
intensification.

***G-IV:*** The G-IV **IP** will be west of the TC and preferably within
the SAL. The 1^st^ leg (**IP-2**) will include a dropwindsonde transect
across the northern boundary of the SAL. This dropwindsonde sequence
will focus on sampling the large humidity gradients across the northern
edge of the SAL. The 2^nd^ (**2-3**) and 3^rd^ (**3-4**) legs of the
flight pattern will intermittently sample the moist tropical environment
out ahead of the TC and north of the SAL. The 4^th^ leg (**4-5**) will
include a dropwindsonde transect across the northern boundary of the SAL
(NE of the TC), intermittent dropwindsondes within the SAL (in the
middle of the flight leg), and a dropwindsonde transect across the
southern boundary of the SAL (southeast of the TC). The northern and
southern dropwindsonde sequences will focus on sampling the large
humidity gradients along the SAL boundaries. The intermittent
dropwindsondes and southern dropwindsonde sequence will concentrate on
sampling the SAL mid-level easterly jet. The 5^th^ (**5-6**) and 6^th^
(**6-FP**) flight legs will include intermittent dropwindsondes that
will help identify how the SAL vertical structure and moisture content
are being modified by the TC circulation closer to the storm.

***P-3:*** The P-3 **IP** will be west of the TC and preferably within
the SAL. The 1^st^ leg (**IP-2**) will include a dropwindsonde transect
across the northern boundary of the SAL. This dropwindsonde sequence
will focus on sampling the large humidity gradients across the northern
edge of the SAL. The 2^nd^ leg (**2-3**) of the flight pattern will
sample the boundary between moist tropical air north of the TC center
and the SAL to the south and will include a penetration of the TC center
of circulation. Particular attention will be focused on sampling dry SAL
air near the TC core. The 3^rd^ leg (**3-4**) will include a
dropwindsonde transect across the northern boundary of the SAL to sample
the humidity gradients at the SAL northern boundary. The 4^th^ leg
(**4-FP**) will sample the boundary between moist tropical air north of
the TC center and the SAL to the south and will include a penetration of
the TC center of circulation. Particular attention will be focused on
sampling dry SAL air near the TC core.

**[Option 3:]{.underline}** Single TC embedded located along the leading
edge of the SAL. These systems are often struggle to intensify as they
are overtaken by the SAL surge, but do occasionally separate from the
SAL and intensify. These systems are often characterized by their
low-level circulations racing out ahead (west) of their mid-level
convection.

***G-IV:*** The G-IV **IP** will be west of the TC. The 1^st^ leg
(**IP-2**) will include intermittent dropwindsonde sampling of the moist
tropical environment out ahead of the TC and west of the SAL. The 2^nd^
(**2-3**) leg will sample the moist tropical environment north of the TC
and west of the SAL followed by a dropwindsonde transect across the
leading edge of the SAL (north of the TC). The 3^rd^ (**3-4**) and 4^th^
(**4-5**) legs of the flight pattern will intermittently sample the SAL
with specific focus on sampling the gradients associated SAL mid-level
easterly jet (typical located along the southern edge of the SAL). The
5^th^ (**5-IP**) flight leg will include intermittent dropwindsonde
sampling of the SAL, followed by a transect across the SAL leading edge,
followed by intermittent dropwindsonde sampling of the moist tropical
environment out ahead of the TC and west of the SAL.

***P-3:*** The P-3 **IP** will be west of the TC. The 1^st^ leg
(**IP-2**) will include intermittent dropwindsonde sampling of the moist
tropical environment out ahead of the TC and west of the SAL. The 2^nd^
leg (**2-3**) of the flight pattern will sample the boundary between
moist tropical air north of the TC center and the SAL to the south and
will include a penetration of the TC center of circulation. Particular
attention will be focused on sampling dry SAL air near the TC core. The
3^rd^ leg (**3-4**) will include intermittent dropwindsonde sampling
within the SAL with specific focus on sampling the gradients associated
SAL mid-level easterly jet (typical located along the southern edge of
the SAL). The 4^th^ leg (**4-FP**) will sample the boundary between
moist tropical air west of the TC center and the SAL to the east and
will include a penetration of the TC center of circulation. Particular
attention will be focused on sampling dry SAL air near the TC core.

> **[Option 4:]{.underline}** Single TC embedded within the SAL
> throughout most or all of its lifecycle. These systems struggle to
> intensify and are often characterized by their low-level circulations
> racing out ahead (west) of their mid-level convection. Depending on
> the proximity of these features, the SAL dry air may be wrapping into
> the TC low-level circulation (western semicircle).
>
> ***G-IV:*** The **IP** will be north of the TC and preferably north of
> the SAL. The 1^st^ leg (**IP-2**) will include a dropwindsonde
> transect across the northern and southern boundaries of the SAL. These
> dropwindsonde sequences will focus on sampling the large humidity
> gradients across the SAL boundaries as well as the SAL mid-level
> easterly jet (typical located along the southern edge of the SAL).
> These scenarios (TC embedded within the SAL) are typically cases where
> the TC is under the influence of a strong SAL easterly jet. The 2^nd^
> leg (**2-3**) of the flight pattern will intermittently sample the
> moist tropical environment south of the SAL. The 3^rd^ leg (**3-4**)
> will include a dropwindsonde sequence that will be focused along the
> dry air inflow region on the west semicircle of the TC. This
> dropwindsonde sequence will sample the intrusion of low humidity SAL
> air into the TC circulation and help to define how the SAL vertical
> structure and moisture content modify as it advects closer to the TC
> core. A final dropwindsonde transect (**4-FP**) will be made across
> the area of high moisture gradients at the SAL northern boundary and
> in the relatively moister tropical environment north and northwest of
> the SAL.
>
> ***P-3:*** The **IP** will be NW of the TC and preferably north of the
> SAL. The 1^st^ leg (**IP-2**) will include a dropwindsonde transect
> across the northern boundary of the SAL. This dropwindsonde sequences
> will focus on sampling the large humidity gradients across the SAL.
> The 2^nd^ leg (**2-3**) of the flight pattern will intermittently
> sample the moist tropical environment south of the SAL and will
> include a dropwindsonde transect across the southern boundary of the
> SAL as well as the SAL mid-level easterly jet (typical located along
> the southern edge of the SAL). The 3^rd^ (**3-4**) and 4^th^ (**4-5**)
> legs will include a dropwindsonde sequence that will be focused along
> the dry air inflow region on the west semicircle of the TC. This
> dropwindsonde sequence will sample the intrusion of low humidity SAL
> air into the TC circulation and help to define how the SAL vertical
> structure and moisture content modify as it advects closer to the TC
> core. The final leg (**4-FP**) will sample the boundary between moist
> tropical air west of the TC center and the SAL to the east and will
> include a penetration of the TC center of circulation. Particular
> attention will be focused on sampling dry SAL air near the TC core.

![](media/image41.jpeg){width="4.0in" height="3.463888888888889in"}

![](media/image42.jpeg){width="4.0in" height="3.463888888888889in"}

Fig. 1: Sample G-IV (top) and P-3 (bottom) flight tracks for a TC
positioned along the southern edge of the SAL

-   Note 1: During the ferry to the **IP**, the G-IV (P-3) should climb
    to \~200 hPa or 41,000 ft (500 hPa or 18,000 ft) as soon as possible
    and climb as feasible to maintain the highest altitude for the
    duration of the pattern.

```{=html}
<!-- -->
```
-   Note 2: In order to capture the SAL structure, particular attention
    should be paid to regions of high moisture gradients across its
    boundaries (G-IV: **IP-2**, **2-3**, and **4-FP**; P-3: **2-3**, and
    **4-FP**).

-   Note 3: The SAL mid-level easterly jet (\~20-50 kt at 600-700 hPa or
    12,000-15,000 ft) may be evident from dropwindsondes deployed near
    the SAL southern boundary (G-IV: **IP-2** and **2-3;** P-3: **2-3**
    and **3-4**).

### ![](media/image43.jpeg){width="3.9298611111111112in" height="3.459722222222222in"}

> ![](media/image44.jpeg){width="3.9298611111111112in"
> height="3.459722222222222in"}
>
> Fig. 2: Sample G-IV (top) and P-3 (bottom) flight tracks for a TC
> emerging from the SAL.

-   Note 1: During the ferry to the **IP**, the G-IV (P-3) should climb
    to \~200 hPa or 41,000 ft (500 hPa or 18,000 ft) as soon as possible
    and climb as feasible to maintain the highest altitude for the
    duration of the pattern.

-   Note 2: The TC may undergo a period of rapid intensification as it
    emerges from the SAL.

-   Note 3: In order to capture the SAL structure, particular attention
    should be paid to regions of high moisture gradients across its
    boundaries (G-IV: **IP-2** and **4-5;** P-3: **IP-2** and **3-4**).

-   Note 4: The SAL mid-level easterly jet (\~20-50 kt at 600-700 hPa or
    12,000-10,000 ft) may be evident from dropwindsondes deployed near
    the SAL southern boundary (G-IV: **5-6** and **6-7**).

> ![](media/image45.jpeg){width="3.95in" height="3.464583333333333in"}
>
> ![](media/image46.jpeg){width="3.95in" height="3.464583333333333in"}
>
> Fig. 3: Sample G-IV (top) and P-3 (bottom) flight tracks for a TC
> along the leading edge of the SAL.

-   Note 1: During the ferry to the **IP**, the G-IV (P-3) should climb
    to \~200 hPa or 41,000 ft (500 hPa or 18,000 ft) as soon as possible
    and climb as feasible to maintain the highest altitude for the
    duration of the pattern.

-   Note 2: The TC will likely struggle to intensify as it is overtaken
    by the SAL. Slow intensification is possible if the TC is able to
    separate from the SAL.

-   Note 3: In order to capture the SAL structure, particular attention
    should be paid to regions of high moisture gradients across its
    boundaries (G-IV: **2-3** and **5-FP**; P-3: **2-3** and **4-FP**).

-   Note 4: The SAL mid-level easterly jet (\~20-50 kt at 600-700 hPa or
    12,000-10,000 ft) may be evident from dropwindsondes deployed near
    the SAL southern boundary (G-IV: **4-5** and **5-FP**; P-3: **2-3**
    and **3-4**).

> ![](media/image47.jpeg){width="5.5in" height="2.829861111111111in"}
>
> ![](media/image48.jpeg){width="5.534027777777778in"
> height="2.8180555555555555in"}
>
> Fig. 4: Sample G-IV (top) and P-3 (bottom) flight track for a TC
> embedded in the SAL for most or all of its lifecycle.

-   Note 1: During the ferry to the **IP**, The G-IV (P-3) should climb
    to \~200 hPa or \~41,000 ft (500 hPa or 18,000 ft) as soon as
    possible and climb as feasible to maintain the highest altitude for
    the duration of the pattern.

-   Note 2: In order to capture the SAL structure, particular attention
    should be paid to regions of high moisture gradients across its
    boundaries (G-IV: **IP**-**2** and **4**-**FP**; P-3: **IP-2** and
    **2-3**).

-   Note 3: The TC low-level circulation may race ahead of its mid-level
    convection due to the influence of the SAL mid-level easterly jet.

-   Note 4: The SAL mid-level easterly jet (\~20-50 kt at 600-700 hPa or
    15,000-10,000 ft) may be evident from dropwindsondes deployed near
    the SAL southern boundary (G-IV: **IP-2**; P-3: **2-3**).

```{=html}
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```
-   

-   

-   

-   **8. Sea-Salt Aerosol and Cloud Base Number Concentration
    Experiment.**

Cloud active nuclei, known as CCN are a critical element of cloud
formation in as much that every droplet of water in the cloud begins by
condensing on one of these nuclei. Numerous types of CCN exist, but all
have one thing in common: all are water soluble, and form solution drops
at high relative humidity.

Sea salt (SSA) is one of the principal aerosol types that are cloud
active (CCN), and large production of this aerosol (Fig. 1) occurs in
high-wind regimes such as hurricanes and winter storms. However, the
rate of production of the SSA as a function of surface windspeed, and
its altitude profile has never before been determined. This fact was
brought to attention most forcefully during the near crash of NOAA-42 in
the North Atlantic in the winter of 2006, when the P-3 engines ingested
so much salt that three of the four engines ceased working. In
hurricanes, SSA obviously affects the cloud microstructure, but the
quantity of this critically important aerosol that is ingested into
cloud base is completely unknown.

**Significance:**

The Tropical Rainfall Mission (TRMM) observations suggest that summer
convective rainfall in the southeastern US might be increased by
pollution-created CCN (Bell et al, 2008), and Dr. D. Rosenfeld, in a
conference paper, indicated that hurricanes might also be affected.
Before any attempt at introducing additional CCN into a hurricane is
made, it is necessary to document the naturally occurring aerosol
spectrum near cloud base and changes in that spectrum with altitude.
This season is a good time to attempt this measurement, as this is the
first season that the new DMT cloud microphysics probes will be
installed. One of these probes, the Cloud Aerosol Spectrometer (CAS)
measures particles as small as 0.6 µm. Due to the high relative humidity
of the hurricane boundary layer, much of the SSA in the sub-cloud base
area are likely to be in the form of solution droplets with diameters \~
2 µm, so the new aerosol probe should be just able to detect them. In
addition, the CAS is equipped with the Particle-by-Particle module,
which enables this device to determine if the particles it observes are
liquid or solid. This has implications for the long-distance transport
of the SSA aerosol, because solution droplets are removed from the air
faster than dry particles, which may be carried to high altitude.

This experiment should be performed in a weaker storm than Isabel 2003
was, with surface windspeeds \< \~120 kt. In order to sample the
sub-cloud base aerosol, it is necessary to fly below cloud base, which
is typically \~2000 ft MSL in a hurricane. The published AOC low-level
flight restrictions only prohibit flights below 1200 ft. MSL, so
sub-cloud base sampling should not be problematic. I therefore propose
to fly 10-min legs in relatively rain-free air outside the eyewall (Fig.
2) beginning at the minimum safe altitude of 1200 ft. MSL, with each
successive 10-min run occurring at about one-half the altitude
difference between 1200 ft. MSL and cloud base. The last pass in this
sequence should occur in-cloud, preferably in the eyewall, but almost
any cloud will do, at about 200 ft. MSL above cloud base.

It is not necessary to fly upwind for this pattern, and each pass might
be accomplished while transiting from one radial azimuth to another.
Passes should be at least 5 min in length, and a 10-min leg is as long
as needed. If longer legs are possible, that is fine, but these are
minimums. The objective is to get legs in as many wind regimes as
practical, from surface windspeeds of 50kts and higher up to maximum
surface windspeeds of \~120 kt. These passes might be attempted at
various radial distances and quadrants of the storm, and all are
required to be attempted during daylight. If the pilots are willing, a
pass just above cloud base in the inner edge of the eyewall is
desirable, radially inside of the heavy precipitation zone. Heavy
precipitation cleanses the air of aerosol, so these measurements are
compromised by heavy rain. Heavy rain is therefore to be avoided.

![](media/image55.jpeg){width="6.499305555555556in"
height="4.874305555555556in"}

Figure 1: Sea-Salt aerosol generation area in Hurricane Isabel (2003).

![](media/image56.png){width="5.819444444444445in"
height="5.836805555555555in"}

Figure 2: An example of where to fly. The exact location is flexible,
since the objective is to measure the sub-cloud aerosol, then the cloud
base droplet spectrum that is produced.

![](media/image57.png){width="6.113194444444445in"
height="3.9868055555555557in"}

Figure 3: How to fly: Lowest pass, min alt., top pass, just above cloud
base, middle pass, about half way in between. Passes do not need to be
back and forth as shown, nor do they need to be made in succession.

References:

Bell, Thomas L, D. Rosenfeld, K.M. Kim, J.M. Yoo, M.I. Lee, M.
Hahnenberger, 2008: Midweek increase in U.S. summer rain and storm
heights suggests air pollution invigorates rainstorms. J. Geophys. Res.
(D. Atmos), **113**, D02209.

[Possibilities and Limitations of Concepts to Modify Hurricanes by Cloud
Seeding with Sub-Micron Hygroscopic
Aerosols](http://www-md3.csa.com/ids70/view_record.php?id=3&recnum=4&log=from_res&SID=5k6r7js91lerie2lbamtckjh32)
[Rosenfeld,
Daniel](http://www-md3.csa.com/ids70/p_search_form.php?field=au&query=rosenfeld+daniel&log=literal&SID=5k6r7js91lerie2lbamtckjh32);
[[Khain,
Alexander]{.underline}](http://www-md3.csa.com/ids70/p_search_form.php?field=au&query=khain+alexander&log=literal&SID=5k6r7js91lerie2lbamtckjh32);
[[Lynn,
Barry]{.underline}](http://www-md3.csa.com/ids70/p_search_form.php?field=au&query=lynn+barry&log=literal&SID=5k6r7js91lerie2lbamtckjh32);
[[Woodley, W.
L.]{.underline}](http://www-md3.csa.com/ids70/p_search_form.php?field=au&query=woodley+w+l&log=literal&SID=5k6r7js91lerie2lbamtckjh32),
4th European Conference on Severe Storms (ECSS 2007), Miramare, Trieste
(Italy), 10-14 Sep 2007

9\. Eyewall Microphysics Experiment

The hurricane eyewall is the place where the energy transformations that
power the storm are realized. As such, it is the place where the
numerical models of the storm, such as HWRF, must get the microphysical
parameterizations right to have any chance of forecasting either changes
in intensity or precipitation, both identified as critical areas of
research in the NOAA Research 5-year Strategic Plan 2005-2010. The new
DMT microphysical probes obtained by AOC respond much faster than the
old PMS probes. In fact, in hurricane work, the old PMS 2D-C and 2D-P
probes were overloaded up to 90% of the time. The newer 2Dgrey probes
were worse, such that 2D-Grey concentrations were 10% of the 2D-P
concentration. The newest DMT probes do not have this problem, and so
should give a better estimate of the number concentration and water
contents than has been possible heretofore. Furthermore, the DMT probes
can measure cloud droplets in the range 2 -- 50 µm range. Droplets in
this size range are fundamental to the growth of larger precipitation,
both raindrops and ice particles. The FSSP-100 probes were unable to
measure cloud droplet concentrations at all. The particle image
measurements were likely to have underestimated the precipitating and
non-precipitating water and ice number concentrations by as much as a
factor of five, because the old 2D‑mono probes were typically overloaded
\> 80% of the time.

Another critical need is the documentation of the partitioning of the
precipitation into its constituents, particularly in the ice particle
regime at high altitude. A critical failing of the present microphysical
parameterizations is the excessive production of graupel in the eyewall
and elsewhere (McFarquar and Black, (2004), Rogers et al, 2007). This
leads to a \> 2 times overestimation of the precipitation production of
the eyewall, and the consequent error in the distribution and production
rate of latent heat in the eyewall adds to the model intensity error.

These data may be collected along any radial penetration of any storm
(Fig. 1), so long as the pilots do not avoid convection. If the pilots
deliberately avoid convection, the precipitation statistics will be
biased toward unrealistic low rain rates. This will lead to improper
parameterizations to the detriment of the model intensity and rainfall
forecasts. An additional requirement is that the aircraft make
penetrations well above the melting level, not just in the rain. It is
the ice microphysics that requires the most critical changes in the
model, and these data cannot be obtained in any other way. Should the
electric field mills be installed, those data are best obtained well
above the melting level also. The highest altitude penetrations possible
are most desirable, especially those at 20000 ft. \< FL \< 26000 ft MSL,
and radials should be flown on Radar altitude rather than the usual
Pressure altitude.

Highly desired is a convection series, such as arc B in Fig. 1. This
high altitude pass does not need to be done this season, but it would be
useful. The last time such a pass was attempted was in 1981, and it is
high time to revisit it. Such a pass should not be attempted in any
storm with a clear eye diameter of \< 20 nm or that is undergoing rapid
deepening, and should last for at least 10 min. A pass such as this will
enable the most accurate documentation of the precipitation and ice
particle production in the eyewall that has ever been made.

![](media/image58.png){width="5.465972222222222in"
height="5.501388888888889in"}

Figure 1: Proposed microphysical investigation passes. Radial passes (A)
may be accomplished at any altitude, in any part of the storm, so long
as the aircraft does not try to avoid precipitation. However,
penetrations at altitudes \> 20,000 ft MSL are highly desirable. A
circumnavigation (B) in the ice at altitude is also highly desired. This
must not occur in any eyewall \< 20 n. mi. in diameter, and should be
maintained for at least 10 min.

References

McFarquar, G. M., and R. A. Black, 2004: Observations of particle size
and phase in Tropical Cyclones: Implications for Mesoscale modeling of
microphysical processes. *J. Atmos. Sci.* **61**, 422-439.

Rogers, R. F., M. L. Black, S. S. Chen, and R. A. Black, 2007: An
Evaluation of Microphysics Fields from Mesoscale Model Simulations of
Tropical Cyclones. Part I: Comparisons with Observations. *J. Atmos.
Sci.*, **64**, 1811-1834.

**10. TC-Ocean Interaction Experiment:**

**Significance and Goals**

This program broadly addresses the role of the ocean and air-sea
interaction in controlling TC intensity by making detailed measurements
of these processes in one or two storms during the 2008 season. Specific
science goals are in two categories:

*Ocean effects on storm intensity.* Upper ocean properties and dynamics
undoubtedly play a key role in determining TC intensity. Modeling
studies show that the effect of the ocean varies widely depending on
storm size and speed and the preexisting ocean temperature and density
structure. The overriding goal of these studies is to provide data on
TC-ocean interaction with enough detail to rigorously test coupled TC
models, specifically:

-   Measure the two-dimensional SST cooling, air temperature, humidity
    and wind fields beneath the storm and thereby deduce the effect of
    the ocean cooling on ocean enthalpy flux to the storm.

-   Measure the three-dimensional temperature, salinity and velocity
    structure of the ocean beneath the storm and use this to deduce the
    mechanisms and rates of ocean cooling.

-   Conduct the above measurements at several points along the storm
    evolution therefore investigating the role of pre-existing ocean
    variability.

-   Use these data to test the accuracy of the oceanic components
    coupled models.

*Ocean boundary layer and air-sea flux parameterizations.* TC intensity
is highly sensitive to air-sea fluxes. Recent improvement in flux
parameterizations has lead to significant improvements in the accuracy
of TC simulations. These parameterizations, however, are based on a
relatively small number of direct flux measurements. The overriding goal
of these studies is to make additional flux measurements under a
sufficiently wide range of conditions to improve flux parameterizations,
specifically:

-   Measure the air-sea fluxes of enthalpy and momentum using ocean-side
    budget and covariance measurements and thereby verify and improve
    parameterizations of these fluxes.

-   Measure the air-sea fluxes of oxygen and nitrogen using ocean-side
    budget and covariance measurements and use these to verify newly
    developed gas flux parameterizations.

-   Measure profiles of ocean boundary layer turbulence, its energy,
    dissipation rate and skewness and use these to investigate the
    unique properties of hurricane boundary layers.

-   Conduct the above flux and turbulence measurements in all four
    quadrants of a TC so as investigate a wide range of wind and wave
    conditions.

Measurements will be made using arrays of profiling and Lagrangian
floats and drifters deployed by AFRC WC-130J aircraft in a manner
similar to that used in the 2003 and 2004 CBLAST program. Additional
deployments have since refined the instruments and the deployment
strategies. MiniMet drifters will measure SST, surface pressure and
windspeed and direction. Thermistor chain Autonomous Drifting Ocean
Station (ADOS) drifters add ocean temperature measurements to 150m. All
drifter data is reported in real time through the Global
Telecommunications System (GTS). Flux Lagrangian floats will measure
temperature, salinity, oxygen and nitrogen profiles to 200m, boundary
layer evolution and covariance fluxes of most of these quantities,
windspeed and scalar surface wave spectra. E-M Lagrangian floats will
measure temperature, salinity and velocity profiles to 200m. Profile
data will be reported in real time on GTS.

Substantial resources for this work will be funded by external sources.
The HRD contribution consists of coordination with the operational
components of the NHC and the 53^rd^ AFR squadron and P-3 survey flights
over the array with SFMR and SRA wave measurements and dropwindsondes.
Twenty dropwindsondes are externally funded.

This work will be coordinated with NASA P-3 deployments of
air-expendable CTD probes, thereby increasing the coverage of the ocean
response. If the deployments occur in the Gulf of Mexico, Loop Current
area, this work will be coordinated with P-3 deployments of AXBTs and
AXCPs to obtain a more complete picture of the ocean response to storms
in this complex region.

**Main Mission description**

P-3 flights will be conducted in collaboration with operational float
and drifter deployments by WC-130J aircraft operated by the AFRES
Command (AFRC) 53^rd^ Weather Reconnaissance Squadron. The P-3 surveys
will provide information on the storm and sea-surface structure over the
float and drifter array.

**Coordination and Communications**

*Alerts* - Alerts of possible deployments will be sent to the 53^rd^
AWRO up to 5 days before deployment, with a copy to CARCAH, in order to
help with preparations. Most of these will be cancelled.

*Initial BTO (Buoy Tasking Order)* - Three days, 72 h before launch, an
initial BTO for float and glider deployments will be sent to the 53^rd^
and CARCAH. The array deployment location will be chosen to be 24-36 h
ahead of the storm or at a radius of less than 25kts, whichever results
in the earlier takeoff time.

*Updated BTOs* -- An updated BTO will be sent two days before launch and
will be included in the CARCAH OUTLOOK message. Another will be sent one
day before launch and included in the CARCAH POD message. Each of these
BTOs should reach CARCAH by 9am EDT.

*Flight day BTOs* -- Two hours before takeoff, an updated BTO will be
sent directly to the 53^rd^, with an info copy to CARCAH. This will be
used for the mission briefing.

*Final BTO*- Final changes can be sent via SATCOM from the CARCAH office
after the flight is airborne, but before the first deployment location
is reached. Only changes in the release positions can be made, not in
the order of releases.

**Flights**

*Day 1- Float and drifter array deployment*- Figure E1 shows the nominal
deployment pattern for the float and drifter array. It consists of two
lines, A and B, set across the storm path with 8 and 4 elements
respectively. The line length is chosen to be long enough to span the
storm and anticipate the errors in forecast track. The element spacing
is chosen to be approximately the RMW~.~ The Lagrangian floats and
thermistor chain drifters (ADOS) are deployed near the center of the
array to maximize their likelihood of seeing the maximum windspeeds and
ocean response. The Minimet drifters are deployed in the outer regions
of the storm to obtain a full section of storm pressure and windspeeds.
The drifter array is skewed one element to the right of the track in
order to sample the stronger ocean response on the right side.

*Day 2.* *P-3* *survey*- Figure E2 shows the nominal P-3 flight path and
dropwindsonde locations during the storm passage over the float and
drifter array. The survey should ideally be timed so that it occurs as
the storm is passing over the drifter array.

The survey includes legs that follow the elements of float/drifter line
'A' at the start and near the end. The survey anticipates that the
floats and drifters will have moved from their initial position since
deployment and will move relative to the storm during the survey.
Waypoints 1-6 and 13-18 will therefore be determined from the real-time
positions of the array elements. Each line uses 10 dropwindsondes, one
at each end of the line; and two at each of the 4 floats, the double
deployments are done to increase the odds of getting a 10m data.

The rest of the survey consists of 8 radial lines from the storm center.
Dropwindsondes are deployed at the eye, at half R~max~, at R~max~, at
twice R~max~ and at the end of the line, for a total of 36 releases.
AXBTs are deployed from the sonobuoy launch tubes at the eye, at R~max~
and at 2 R~max~. This AXBT array is focused at the storm core where the
strongest air-sea fluxes occur; the buoy array will fill in the SST
field in the outer parts of the storm. In this particular example, the
final two radials have been moved after the second float survey to avoid
upwind transits. For other float drift patterns, this order might be
reversed.

It is highly desirable that this survey be combined with an SRA surface
wave survey because high quality surface wave measurements are essential
to properly interpret and parameterize the air-sea fluxes and boundary
layer dynamics, and so that intercomparisons between the float wave
measurements and the SRA wave measurements can be made.

**Extended Mission Description**

If the storm remains strong and its track remains over water, a second
or possibly third oceanographic array may be deployed, particularly if
the predicted track lies over a warm ocean feature predicted to cause
storm intensification (Fig. E3). The extended arrays will consist
entirely of thermistor chain and minimet drifters, with 7 elements in a
single line. As with the main mission, the spacing and length of the
line will be set by the size of the storm and the uncertainty in the
forecast track.

Mission timing and coordination will be similar to that described above.
P-3 overflights would be highly desirable.

![](media/image59.png){width="4.739583333333333in"
height="4.593055555555556in"}

Figure E1. Float and drifter array deployed by AFRC WC-130J aircraft.
The array is deployed ahead of the storm with the exact array location
and spacing determined by the storm speed, size and the uncertainty in
the storm track. The array consists of a mix of ADOS thermistor chain
(A) and minimet (M) drifters and gas (G) and EM (E) Lagrangian floats.
Three items are deployed at locations 3, 4 and 5, two items at location
3 and one item elsewhere.

![](media/image60.png){width="5.603472222222222in" height="5.9in"}

Figure E2. P-3 pattern over float and drifter array. The array has been
distorted since its deployment on the previous day and moves relative to
the storm during the survey. The pattern includes two legs along the
array (waypoints 1-6 and 13-18) and an 8 radial line survey.
Dropwindsondes are deployed along all legs, with double deployments at
the floats. AXBTs are deployed in the storm core.

![](media/image61.png){width="5.995138888888889in"
height="3.502083333333333in"}

Figure E3- Extended Mission. Two additional drifter arrays will be
deployed along the storm track.

**IFEX MISSIONS (Continued)**

**11. Hurricane Synoptic Surveillance**

**Program Significance:** Accurate numerical TC forecasts require the
representation of meteorological fields on a variety of scales, and the
assimilation of the data into realistic models. Omega dropwindsonde
(ODW) observations from P-3 aircraft obtained between 1982 and 1996
during the Hurricane Synoptic Flow Experiment produced significant
improvement in the guidance for official track forecasts. Since 1997,
more than 150 operational Synoptic Surveillance missions have been flown
with the NOAA G-IV jet in the environments of TCs threatening the United
States coastline; some of these have been supplemented with
dropwindsonde observations from one or two P-3 or USAF C-130 aircraft.
An improved dropwindsonde based on GPS has been developed by the
National Center for Atmospheric Research and has replaced the ODW. With
further operational use of the G-IV aircraft, and as other mobile
observing platforms become available, optimal sampling and utilization
techniques must be devised to provide the greatest possible improvement
in initial condition specification.

**Objectives:** The goal of synoptic surveillance is to improve landfall
predictions of TCs by releasing dropwindsondes in the TC environment.
These data will be used by NCEP to prepare objective analyses and
official forecasts through their assimilation into operational numerical
prediction models. Because the atmosphere is known to be chaotic, very
small perturbations to initial conditions in some locations can amplify
with time. However, in other locations, perturbations may result in only
small differences in subsequent forecasts. Therefore, targeting
locations in which the initial conditions have errors that grow most
rapidly may lead to the largest possible forecast improvements. Locating
these regions that impact the particular forecast is necessary. When
such regions are sampled at regularly spaced intervals the impact is
most positive. The optimal targeting and sampling strategies is an
ongoing area of research.

A number of methods to find targets are being investigated. Potential
vorticity diagnosis can help to find the cause of forecast failure.
Singular vectors of the linearized equations of motion can estimate the
growth of small perturbations in the model. Related strategies involve
the sensitivity vector, and quasi-inverse linear method. A fully
nonlinear technique uses the operational NCEP Ensemble Forecasting
System in which initially random perturbations are repeatedly evolved
and rescaled over a relatively short cycling time. The ensemble spread
is related to local Lyapunov vectors and, therefore, define the fastest
growing modes of the system. Changes to initial conditions due to
synoptic surveillance grow (decay) in regions of large (small)
perturbation in the operational NCEP Ensemble Forecasting System.
Therefore, these modes provide a good estimate of the locations in which
supplemental observations are likely to have the most impact. However,
though this method can find locations of probable error growth in the
model globally, it does not distinguish those locations, which impact
the particular forecast from those that do not. A more generalized
method that can use any dynamical ensemble forecast system is the
Ensemble Transform Kalman Filter. This method transforms an ensemble of
forecasts appropriate for one observational network into one appropriate
for other observational networks. Ensemble forecasts corresponding to
adaptations of the standard observational network are computed, and the
expected prediction error variance at the observation time is computed
for each potential network. The prediction error variance is calculated
using the distances between the forecast tracks from all ensemble
members and the ensemble mean. These methods are currently undergoing
testing with Observing System Experiments (OSEs) to discern an optimal
targeting technique.

**Links to IFEX:** This supports the following NOAA IFEX goals:

E)  **Goal 1**: Collect observations that span the TC lifecycle in a
    variety of environments.

**Mission Description:** To assess targeting strategies a relatively
uniform distribution of dropwindsondes will be released over a minimal
period by various aircraft (the NOAA G-IV and AFRES C-130s) operating
*simultaneously.* Specific flight tracks will vary depending on such
factors as the location of the storm, relative both to potential bases
of operation and to particular environmental meteorological features of
interest. A sample mission is shown in Fig. SYN-1. The two C-130
aircraft and the G-IV will begin their missions at the same time.
Subject to safety and operational constraints, each aircraft will climb
as rapidly as possible, then proceed, step-climbing, along the routes
assigned during preflight. *It is particularly important that both
aircraft climb to and maintain the highest possible altitude as early
into the mission as aircraft performance and circumstances allow, and
attain additional altitude whenever possible during the mission.*

Of paramount importance is the transmission of the dropwindsonde data to
NCEP for timely incorporation into operational analyses, models,
forecasts, and warnings. Operational constraints dictate an 0600 or 1800
UTC departure time, so that most of the dropwindsonde data will be
included in the 1200 or 0000 UTC analysis cycle. Further, limiting the
total block time to 9 h allows adequate preparation time for aircraft
and crews to repeat the mission at 24-h intervals. These considerations
will ensure a fixed, daily real-time data collection sequence that is
synchronized with NCEP analysis and forecasting schedules.

**Saharan Air Layer Module**: This module will be executed by HRD, using
HRD resources and will be carried out within the constraints of the
pre-determined operational flight track. Additional intermediate
dropwindsondes (HRD-supplied) may be requested along the flight track to
target specific areas of interest. Dropwindsondes will be launched from
the G-IV (flying at \~200 hPa or \~41,000 ft) or the P-3 (flying at
\~500 hPa or \~20,000 ft) along the operational Synoptic Surveillance
flight pattern. These additional release locations will be selected
using real-time GOES SAL tracking imagery from UW-CIMSS and mosaics of
SSM/I total precipitable water from the Naval Research Laboratory.
Specific effort will be made to gather atmospheric information within
the SAL as well as regions of high moisture gradients across its
boundaries. The main goals are to:

-   Better understand how the SAL dry air, mid-level easterly jet, and
    suspended mineral dust affect Atlantic TC intensity change.

-   Include the moisture information from the dropwindsondes in
    operational parallel runs of the GFS. The impact of this data on the
    GFS initial or forecast humidity fields and its forecasts of TC
    track and intensity will be assessed.

Several SAL/TC interaction scenarios are candidates:

Figure SYN-2 shows a single TC located along the southern edge of the
SAL. Depending on the proximity of these two features, the SAL dry air
may be wrapping into the TC low-level circulation (western quadrants).
Dropwindsonde sequences will be focused along this dry air inflow region
(west of the TC), across regions of high moisture gradients at the SAL
leading edge (northwest of the TC), and across the southern boundary of
the SAL (north and northeast of the TC). The SAL mid-level jet will also
be sampled in the region of the latter transect.

Figure SYN-3 shows a single TC is embedded within the SAL and
intensifies upon emerging. These systems are often candidates for rapid
intensification. Dropwindsonde transects perpendicular to the northern
boundary of the SAL and near to possible points of the TC emergence from
the SAL are desirable. Additional transects will be focused along the
SAL southern boundary (south of the TC). The SAL mid-level jet will also
be sampled, particularly along those transects on the eastern sides of
the TC.

> Figure SYN-4 shows a single TC embedded within the SAL throughout most
> or all of its lifecycle. These systems struggle to intensify and are
> often characterized by their low-level circulation racing out ahead
> (west) of their mid-level convection. Depending on the proximity of
> the TC to the SAL, the SAL dry air may be wrapping into its low-level
> circulation (western semicircle). Dropwindsonde sequences will be
> focused along this dry air inflow region (west of the TC), across
> regions of high moisture gradients at the SAL northern boundary (north
> of the TC), and across regions of high moisture gradients at the SAL
> southern boundary (east of the TC). The SAL mid-level jet will also be
> sampled, particularly in the region of the latter transect.

![](media/image49.pct){width="6.4992125984251965in"
height="5.825590551181103in"}

Figure SYN-1: Sample Environmental Patterns

• Note 1: During the ferry to the **IP**, the C-130 aircraft will climb
as quickly as possible.

• Note 2.: During the ferry to the **IP**, The G-IV should climb to the
41,000 ft (200 hPa) as soon as possible and climb as feasible to
maintain the highest altitude for the duration of the pattern.

> ![](media/image52.jpeg){width="3.6145669291338582in"
> height="3.1354330708661418in"}
>
> ![](media/image53.jpeg){width="3.6041666666666665in" height="3.125in"}
>
> Figure SYN-3: Sample flight track for a TC emerging from the SAL.

###  {#section-4 .unnumbered}

> ![](media/image54.jpeg){width="6.15in" height="3.1798611111111112in"}
>
> Figure SYN-4: Sample flight track for a TC embedded in the SAL for
> most or all of its lifecycle.

-   Note 1: During the ferry to the **IP**, the P-3 aircraft will climb
    to the \~500 hPa level (\~20,000 ft). The 400-hPa level (\~25,000
    ft) should be reached as soon as possible and maintained throughout
    the remainder of the pattern, unless icing or electrical conditions
    require a lower altitude.

-   Note 2: During the ferry to the **IP**, The G-IV should climb to the
    \~200 hPa (\~41,000 ft) as soon as possible and climb as feasible to
    maintain the highest altitude for the duration of the pattern.

-   Note 3: In order to capture the SAL structure, particular attention
    should be paid to regions of high moisture gradients across its
    boundaries.

Supplemental: Operational Base Maps

![](media/image62.jpeg){width="9.194444444444445in" height="5.55in"}

Map 1: Primary Atlantic operating bases and approximate operating ranges
for the NOAA G-IV.

**Supplemental: Operational Base Maps (continued)**

![](media/image63.jpeg){width="9.194444444444445in" height="5.55in"}

Map 2: Primary Atlantic operating bases and approximate operating ranges
for the NOAA P-3.