# 5 Research Priorities

The operational needs of the tropical cyclone forecast and warning
centers, as summarized in section 4.1, can be characterized by the
following seven tropical cyclone--related, day-to-day operational
forecast and warning categories (or a combination of these categories):

+--------------------------+-------------------------------------------+
| -   Intensity            | -   Storm surge                           |
+--------------------------+-------------------------------------------+
| -   Structure            | -   Precipitation                         |
+--------------------------+-------------------------------------------+
| -   Track                | -   Observations                          |
+--------------------------+-------------------------------------------+
| -   Sea state            |                                           |
+--------------------------+-------------------------------------------+

As shown in chapter 4, meeting the operational needs will require
continued advances in observations, data assimilation technologies, and
tropical cyclone NWP models. Absolutely essential to these advances is
sufficient human and infrastructure resources for tropical cyclone R&D
and the transition of R&D results to operations, along with sufficient
human and infrastructure resources for the operational NWP environment.
This chapter focuses on the tropical cyclone research priorities to aid
in further enhancing the future capabilities of the tropical cyclone
forecast and warning centers.

## 5.1 Research Priorities in Atmospheric and Ocean Science

![](media/image1.jpeg){width="4.0in" height="2.0952755905511813in"}Table
5-1 lists the JAG/TCR's recommended priorities for tropical cyclone
research in atmospheric and ocean science. When the terms "basic" or
"applied" research are used in this chapter, refer to figure 5-1 and the
definitions in section 3.5.3 as a guide in distinguishing between the
two types of research. The JAG/TCR has formulated these priority topics
to respond to the operational needs and capability limitations discussed
in chapters 3 and 4. The priorities and their formulation reflect the
many discussions and iterations by the JAG/TCR regarding agency views on
priorities for tropical cyclone R&D in atmospheric and ocean science. It
provides a consensus view from the Federal agencies represented on the
JAG/TCR and is intended to become part of a "living document" to be
updated annually. Additionally, the OFCM intends to structure portions
of the annual IHC around these research priorities.

The research priorities are arranged under three main areas: (1) General
Research and NWP Modeling Topics, (2) NWP Model Development Topics, and
(3) Observations and Observing

**Table 5-1. Research Priorities in Atmospheric and Ocean Science**

+------------------------------------------------+-----+--------------+
| **Research Topics**                            | **T | **Plan       |
|                                                | ype | R            |
|                                                | of  | eferencesa** |
|                                                | Res |              |
|                                                | ear |              |
|                                                | ch\ |              |
|                                                | **B |              |
|                                                | =   |              |
|                                                | B   |              |
|                                                | asi |              |
|                                                | c;\ |              |
|                                                | A   |              |
|                                                | =A  |              |
|                                                | ppl |              |
|                                                | ied |              |
+------------------------------------------------+-----+--------------+
| **General Research and NWP Modeling Topics**   |     |              |
+------------------------------------------------+-----+--------------+
| 1\. Role of inner core processes on intensity  | B   |              |
| and structure changes (e.g., eyewall           |     |              |
| replacement cycles, mixing).                   |     |              |
+------------------------------------------------+-----+--------------+
| 2\. Relative role of vortex versus environment | B,A |              |
| in influencing intensity and structure (e.g.,  |     |              |
| role of vortex mixing and resiliency \[vortex  |     |              |
| Rossby waves and stability\]).                 |     |              |
+------------------------------------------------+-----+--------------+
| 3\. Role of rainbands on intensity and         | B   |              |
| structure changes.                             |     |              |
+------------------------------------------------+-----+--------------+
| 4\. Role of dry air, midlevel easterly jet,    | B,A |              |
| and suspended mineral dust from Saharan Air    |     |              |
| Layer on intensity and structure changes.      |     |              |
+------------------------------------------------+-----+--------------+
| 5\. Role of vertical shear of horizontal wind  | B,A |              |
| on intensity and structure changes.            |     |              |
+------------------------------------------------+-----+--------------+
| 6\. Tropical cyclone genesis.                  | B,A | §3.5, 4.1,   |
|                                                |     | 5.2.1; Tb.   |
|                                                |     | 4-1          |
+------------------------------------------------+-----+--------------+
| 7\. Determinants of structure and relationship | B   |              |
| with preexisting wave disturbance;             |     |              |
| relationship between structure and intensity.  |     |              |
+------------------------------------------------+-----+--------------+
| 8\. Role of ocean; role of oceanic heat        | B,A |              |
| content.                                       |     |              |
+------------------------------------------------+-----+--------------+
| 9\. Physics                                    | B,A |              |
|                                                |     |              |
| > a\. Relative importance of physics (e.g.,    |     |              |
| > air-sea fluxes, microphysics, convection) on |     |              |
| > intensity and structure changes in various   |     |              |
| > environments (e.g., sheared vs. non-shear)   |     |              |
| >                                              |     |              |
| > b\. Processes within atmosphere-ocean        |     |              |
| > boundary layer on intensity/structure        |     |              |
| > changes (i.e., momentum and enthalpy         |     |              |
| > fluxes); role of boundary layer wind         |     |              |
| > structure on the transfer of energy and      |     |              |
| > mass.                                        |     |              |
| >                                              |     |              |
| > c\. Role of radiation and interaction of     |     |              |
| > radiation with microphysics.                 |     |              |
| >                                              |     |              |
| > d\. Role of vortex-scale moisture            |     |              |
| > convergence and cloud microphysics in        |     |              |
| > precipitation processes.                     |     |              |
| >                                              |     |              |
| > e\. Role of landfall effects (e.g., surface  |     |              |
| > flux changes) on intensity, structure, and   |     |              |
| > precipitation processes.                     |     |              |
| >                                              |     |              |
| > f\. Resolution studies (considering a-e      |     |              |
| > above) to determine what scales can be       |     |              |
| > explicitly resolved.                         |     |              |
+------------------------------------------------+-----+--------------+
| **NWP Model Development Topics**               |     |              |
+------------------------------------------------+-----+--------------+
| 1\. Tropical cyclone vortex initialization;    | A   |              |
| ocean initialization                           |     |              |
+------------------------------------------------+-----+--------------+
| 2\. Atmosphere-ocean boundary layer for        | B,A |              |
| coupled air-sea-wave problem; momentum (wave   |     |              |
| induced drag) and enthalpy fluxes (sea spray   |     |              |
| complexity).                                   |     |              |
+------------------------------------------------+-----+--------------+
| 3\. Land surface coupling: Complexity of       | A   |              |
| coupling w/HWRF; sensitivity of LSM on track,  |     |              |
| intensity and structure, precipitation         |     |              |
+------------------------------------------------+-----+--------------+
| 4\. Coupling of HWRF with hydrology/inundation | A   |              |
| models.                                        |     |              |
+------------------------------------------------+-----+--------------+
| 5\. Verification for three dimensional,        | A   |              |
| high-resolution NWP model for all phases of    |     |              |
| the tropical cyclone life cycle; varying       |     |              |
| atmosphere/ocean environment.                  |     |              |
+------------------------------------------------+-----+--------------+
| 6\. Diagnostic techniques to further increase  | A   |              |
| the utility of global models (e.g., NCEP,      |     |              |
| UKMO, NOGAPS) in forecasting tropical cyclone  |     |              |
| genesis.                                       |     |              |
+------------------------------------------------+-----+--------------+
| 7\. Development of advanced, high-resolution   | A   |              |
| probabilistic guidance (e.g., (ensembles);     |     |              |
| optimal ensemble construction and              |     |              |
| configuration; value of very high-resolution   |     |              |
| deterministic forecasts vs. ensembles          |     |              |
+------------------------------------------------+-----+--------------+
| **Observations and Observing Strategies**      |     |              |
+------------------------------------------------+-----+--------------+
| 1\. Where to take observations for             | A   |              |
| initialization of hurricane vortex; what is    |     |              |
| the hurricane "core" circulation and how do we |     |              |
| define?                                        |     |              |
+------------------------------------------------+-----+--------------+
| 2\. Alternatives and tradeoffs for observing   | A   |              |
| storms and their environment with in situ      |     |              |
| (e.g., buoys, aircraft) and remote sensors     |     |              |
| (e.g., satellite).                             |     |              |
+------------------------------------------------+-----+--------------+
| 3\. Required observations to support model     | A   |              |
| diagnostics and verification (e.g., IFEX       |     |              |
| effort led by HRD).                            |     |              |
+------------------------------------------------+-----+--------------+
| 4\. Techniques to evaluate the uncertainty and | A   |              |
| representativeness of observations and use of  |     |              |
| observations for initializing NWP models.      |     |              |
+------------------------------------------------+-----+--------------+
| 5\. New observational technologies.            | B,A |              |
+------------------------------------------------+-----+--------------+

a \[Plan Reference column to be completed with section numbers and table
numbers from chapters 1-6\]

Strategies. The first area, General Research and NWP Modeling Topics,
contains scientific and modeling issues that need to be addressed. The
second area, NWP Model Development Topics, strictly focuses on NWP model
development challenges that require focused research. The third area,
Observations and Observing Strategies, highlights the use of
observations to aid in providing improved analysis and forecast
guidance. Many of the research priorities listed in table 5-1 are
explicitly discussed in the body of this report. The right-hand column
in table 5‑1 indicates the applicable locations within the report body
where that priority is discussed. The subsections below provide
additional information, summarized from the JAG/TCR deliberations, on
the rationale for these research priorities. In some instances, the
subsections include specific questions of importance for a particular
research topic/area, as an aid in clarifying the research required.

### 5.1.1 General Research and NWP Modeling Topics

The gains made over the past several decades in our understanding and
forecasting of tropical cyclones have paralleled the improvements in
observational capabilities (e.g., instrumented aircraft, land-based and
airborne Doppler radars, usage and quality of satellite data), improved
representation of model physics in NWP models, and the use of these
observations through more sophisticated data assimilation capabilities.
The fact that a tropical cyclone spends the majority of its life over
the tropical ocean, where few data are available, has forced the
community to pioneer mobile observing strategies in order to provide
critical observations for the operational forecast and model
communities. In addition, these techniques have evolved to include
measurements of the upper-ocean and atmosphere in the vicinity of the
storm. However, continued exploitation of existing observations via
advanced data assimilation systems and improved numerical weather
prediction (NWP) models would enhance tropical cyclone track and
intensity forecast guidance provided to forecasters. In the case of
intensity, wind structure, and precipitation associated with tropical
cyclone landfall, an aggressive research program is needed that will
provide the understanding, technology, and applications necessary to
further enhance NWP models and forecast guidance products.

The modest improvement in the intensity forecasts may be attributed to
deficiencies in the current prediction models, including items such as
inadequate initialization of the hurricane vortex and inadequate
representation of the atmosphere-ocean boundary layer (Ginis et al.
2006a and 2006b). Research is required to better understand the physical
processes that contribute to tropical cyclone intensity and wind field
changes (i.e., structure), and how those processes are represented in
operational forecast models. A synergism between observations and NWP
models is required to isolate the important physical processes.
High-quality, high-resolution observations are critical to model
parameterizations for atmospheric, oceanic, or coupled processes. This
research is essential for improving track, intensity and wind structure,
and quantitative precipitation forecasts.

To most effectively support improvements in operational forecasts,
modeling research must be closely integrated with operational models and
priorities. This research develops an improved understanding of key
physical processes that influence tropical cyclones such as the
following:

#### Internal Vortex Dynamics

Numerical models must be able to simulate the development and breaking
of unstable vortex-Rossby waves in the eyewall (e.g., Montgomery and
Kallenbach 1997; Schubert et al. 1999). This will require a fully
three-dimensional turbulence scheme because the horizontal shears in the
eyewall region and around convective cells are very strong and capable
of producing resolvable turbulence.

The role of vortex-scale moisture convergence and cloud microphysics is
a priority topic because microphysical parameterizations are sensitive
to whether or not the convective updrafts and downdrafts are correctly
represented in the model. The effects on ice nucleation processes by
mineral dust (e.g., Saharan Air Layer) are also not understood.

The following topics also need to be addressed:

-   Role of vortex mixing and resiliency (e.g., vortex-Rossby waves and
    vortex stability)

-   Role of rainbands and eyewall replacement cycles

-   Role of asymmetries in the evolution of the vortex core

#### Interaction of the Vortex with its Environment

Fine-scale structure must be considered in the context of the
interactions of the tropical cyclone with its environment. In
particular, the effects of vertical shear of horizontal wind play a
critical role in storm intensity and rain forecasts. Interactions with
vertical wind shear are an important part of current statistically-based
intensity forecast models and have been the subject of considerable
research (e.g., DeMaria 1996; DeMaria and Kaplan 1994, 1999). Frank and
Ritchie (2001) and Rogers et al. (2002) show that the impacts of
vertical shear on both inner-core structure and rainfall patterns of
tropical cyclones are significant. Other topics that need to be
addressed include the following:

-   Distinction between a trough that leads to a storm\'s
    intensification upon interaction and one that leads to a storm\'s
    decay

-   Role of dry air, mid-level easterly jet, and suspended mineral dust
    from Saharan Air Layer

-   Interactions that lead to vortex asymmetries and changes in vortex
    dynamics

#### Tropical Cyclogenesis 

A critical unresolved aspect of tropical cyclone intensity change is how
a vortex reaches sufficient intensity to enable the storm to continue to
intensify (cyclogenesis). Simulations suggest that the building blocks
of the tropical cyclone intensification process are cores of deep
cumulus convection that produce large values of cyclonic vorticity on
cloud scales via the stretching of already vorticity-rich air in the
pre-storm environment. Subsequent intensification is hypothesized to be
a two-stage process. In the first stage, multiple
convectively-concentrated low-level potential vorticity anomalies are
produced, while in the second stage the multiple potential vorticity
anomalies undergo merger and axisymmetrization as part of the
intensification of the warm-core vortex. Reasor et al. (2005) explored
the first stage of the intensification through an examination of the
genesis of Hurricane Dolly (1996) using an analysis of airborne Doppler
radar observations. They found that the early development of Dolly
supports a stochastic view of tropical cyclone genesis in which multiple
lower-to-middle-tropospheric mesoscale cyclonic circulations are
involved in building the surface cyclonic circulation. These findings
suggest that the development of the initial low-level cyclonic
circulation is a bottom-up process that fundamentally occurs as
convective scale vortices amalgamate and intensify. A number of
fundamental questions arise with respect to genesis, including the
following:

-   What processes lead to a disturbance becoming a tropical depression
    and subsequently a tropical storm?

-   What is the mesoscale/synoptic-scale vorticity structure in the
    upper troposphere during cyclogensis and how does it modulate the
    convection environment?

-   How does convection respond to the presence of pre-existing
    vorticity anomalies at different levels?

-   How does deep moist convection modify the vorticity associated with
    the triggering disturbance?

#### Determinants of Structure

This topic includes determinants of wind radii, the relationships
between wind structure and preexisting wave disturbance; and the
relationship between structure and intensity. Many basic controlling
parameters that define the structure of hurricanes are not yet
understood and remain difficult to predict. For example, not much is
known about what determines the radius of maximum wind (RMW), one of the
most important dynamical properties necessary to describe any given
hurricane.

#### Interaction of the Vortex with the Underlying Surface

Tropical cyclones draw energy from the ocean and cool the ocean by
wind-induced surface fluxes and vertical mixing in the ocean. The
extreme high winds, intense rainfall, large ocean waves, and copious sea
spray push the surface-exchange parameters for temperature, water vapor,
and momentum into untested new regimes. Air-sea interactions in the
eyewall region are largely unknown, due primarily to a lack of
observations at the air-sea interface. The heat, moisture, and momentum
exchange coefficients under the high-wind conditions are difficult to
determine. Partially resolvable boundary layer secondary circulations
further modulate surface fluxes and must be included in new
parameterizations. Other topics that need to be addressed include the
following:

-   Boundary layer wind structure and the transfer of energy and mass

-   Role of air-sea flux of energy and water

-   Impact of wave field on surface transfer of energy and mass

-   Impact of spatial variability in the air-sea fluxes within and
    surrounding the eye, and their relationship to upper ocean processes

-   Landfall effects on the boundary layer wind structure and transfer
    of energy and mass

### 5.1.2 NWP Model Development Topics

#### Ocean Initialization

Since the next generation, operational, high-resolution tropical cyclone
models (HWRF Air-Sea-Land Hurricane Prediction System and COAMPS
Tropical Cyclone System) are fully coupled systems, initialization of
the ocean from a basin scale ocean model with a cycled ocean data
assimilation system (ODAS) must provide initial conditions for the
models.

#### Atmosphere-Ocean Boundary Layer

Research is needed to develop improved air-sea parameterizations for
tropical cyclone high wind regimes and improved wave drag relationships.
Specifically, the incorporation of sea spray in the next generation,
operational, high-resolution tropical cyclone model, with research that
investigates the impact of feedback processes of the evaporative and
heat transfer in the planetary boundary layer (PBL) on tropical cyclone
intensity and structure. A second research aspect of the air-sea is
problem is to improve the representation of the wave induced drag.
Preliminary studies have shown that under hurricane wind conditions, the
younger waves produce smaller drag such that hurricane intensity and
structure can be significantly affected by the explicit simulation of
surface waves (see section 3.3.2).

#### Land Surface Coupling

During tropical cyclone landfall, flood forecasting depends critically
on the precipitation distribution, hydrological and topographic factors,
and the tropical cyclone size and motion. The HWRF Air-Sea-Land
Hurricane Prediction System will be coupled with a land surface and
hydrology system for prediction of inland flooding to address this
critical service requirement (see section 4.4.2). The impact of the
modeled hydrological cycle on tropical cyclone precipitation has yet to
be explored. Some work has been done on coupling an LSM to the GFDL
hurricane model and the HWRF system will use the operational Noah LSM.
However, the full sensitivity of the HWRF for track, intensity and
structure, and precipitation needs to be explored.

#### Development of Advanced, High-Resolution Probabilistic Guidance (e.g., Ensembles)

For the improvement of tropical cyclone intensity and structure
guidance, studies need to be conducted to determine the feasibility,
optimal construction, and configuration of HWRF and/or COAMPS ensembles
(e.g., ensemble resolution and ensemble members within the constraints
of the operational environment). In addition to providing explicit
HWRF/COAMPS guidance for intensity and structure, these studies will
have a large impact on next generation tropical cyclone challenges
involving the forcing for wave and storm surge models.

#### Relative Value of Very-high-resolution Deterministic Forecasts and Ensembles

The improvement of intensity and structure guidance needs to be
investigated using very high-resolution deterministic guidance from the
HWRF Air-Sea-Land Hurricane Prediction System or COAMPS Tropical Cyclone
System (\< 4 km) versus using ensembles from a lower resolution version
of these NWP systems. From an operational perspective, is it better to
have one solution \[deterministic\] from a very high-resolution model or
a range of uncertainty, as determined by running ensembles with a lower
resolution version of the model?

#### Research Studies

Research studies must take full advantage of the operational
capabilities (HWRF Air-Sea-Land Hurricane Prediction System and/or
COAMPS Tropical Cyclone System). These systems must be used for both
testing of potential operational improvements as well as for exploratory
research which is beyond immediate operational capabilities. Impacts of
improved intensity forecasts on tropical cyclone track must also be
evaluated to ensure no degradation of present track forecasting
capability. A focused and directed research program, culminating in
transition-to-operations---which uses the HWRF Air-Sea-Land Hurricane
Prediction System and/or COAMPS Tropical Cyclone System---must be
promoted and supported. Direction for each element of the program must
come from operational NOAA or NRL/FNMOC components. Studies can include
observing system impact studies (which can feed back on future
deployment of observations), sensitivity studies to numerical forecast
system resolution, and preliminary tests of upgrades to fundamental
components.

### 5.1.3 Observations and Observing Strategies

Continuing to advance observational capabilities for tropical cyclone
analysis and numerical weather prediction is vital to the Nation's
tropical cyclone program. To maximize the benefit from limited
resources, research is needed to systematically evaluate observing
systems, develop observing system requirements, and document the
benefits that can be expected from new observing systems to forecasts of
tropical cyclones and related hazards.

The rest of this section will expound upon the research priority:
"Techniques to evaluate the uncertainty and representativeness of
observations and use of observations for initializing NWP models." To
evaluate current and potential new observing systems and/or sampling
strategies, techniques (likely statistical) need to be developed that
address the uncertainty and representativeness of observations. In
particular there are two places these uncertainties are applicable: (1)
in real-time estimates of the storm structure and intensity; and (2) use
of observations for initializing NWP models.

A good example for (1) above is the "best-track" estimate of tropical
cyclones (see figure 1-3 for an example). As seen in figure 5-2, with
all of the points on the curve relating peak wind estimates versus time,
there is are large differences (scatter). Some of the differences are
due to the storm structure (particularly for the aircraft and
dropwindsonde observations), whereas other differences are due to
uncertainty in the type of estimate used (e.g., Dvorak \[regular and
automated\], aircraft, SFMR, etc.). Each of these observational tools
has an uncertainty. The uncertainty needs to be characterized to better
quantify the goodness of the "best-track" estimates. Additionally, the
uncertainty will be applicable to NWP model initialization, as the
uncertainty/error of each data type used in the model is an important
element. Another important aspect associated with NWP models is how the
observational data is best utilized. For example, for surface
observations, how do we extend the influence of the observation in the
vertical? For dropwindsondes and Doppler (airborne and land-based)
observations, how to we extend the influence of these observations
horizontally or temporally to best utilize them?

![](media/image2.jpeg){width="5.5in" height="4.125in"}

> **Figure 5-2.** Best-track estimate of Hurricane Frances intensity as
> determined in the post-analysis of all available data (e.g.,
> satellite, aircraft, GPS dropwindsondes, etc.). Credit: TPC/NHC

## 5.2 Climate Research Priorities---Intraseasonal, Interannual, and Longer-Term Variability of Tropical Cyclones

This section details the climate research priorities regarding
intraseasonal, interannual, and longer-term variability of tropical
cyclones. Tropical cyclone activity varies on multiple temporal scales
from intraseasonal, interannual, decadal, and multidecadal timeframes.
Paleoclimate work even suggests distinct variations on the centennial
and millennium scales. Increasingly, there are requests for predictions
on all of these timescales which NOAA and other agencies---both public
and private---are striving to provide.

On the intraseasonal---or monthly---timescales, research efforts have
demonstrated the impact of features such as the Madden-Julian
Oscillation (MJO) to produce clustering in time of tropical cyclone
occurrences. These tend to last for 20-30 days of active and quiet
cycles each, primarily for tropical cyclones forming in the low
latitudes. NOAA is currently responsible for predictions up to two weeks
in advance for global tropical cyclone activity outlooks based upon
anticipated MJO phases. These are produced through a combination of
statistical techniques, numerical model guidance (such as the Global
Forecast System), and forecaster input. Continued research into the
physical mechanisms for intraseasonal variability, as well as improved
statistical and numerical model tools, is needed.

Seasonal forecasts have been issued for the Atlantic basin over the last
two decades, and NOAA has been providing official predictions since
1998. NOAA\'s predictions are released in late May (at the beginning of
the Atlantic and Northeast Pacific hurricane seasons) and in early
August (for the Atlantic, at the onset of the traditionally most active
portion of the season). These are based upon pre-season assessments of
current oceanic and atmospheric factors known to influence tropical
cyclone activity (such as SSTs, sea-level pressures, tropospheric
vertical wind shear, etc.) and how these may vary by the peak (August to
October) of the hurricane season. This is accomplished by use of
statistical tools (such as canonical correlation analyses and multiple
regression techniques), numerical models (such as NOAA\'s Climate
Forecast System), and forecaster interpretations of current climate
trends. Often it is difficult to assess what components of the current
oceanic/atmospheric conditions are transient (intraseasonal
oscillations) versus longer-term (interannual and decadal) variations,
in deciding how the environment may behave during the peak of the
season. One of the key factors for interannual predictions is the El
Nino-Southern Oscillation (ENSO) phenomenon. Skillful long-lead
forecasts of ENSO have been problematic, which is one of the reasons why
NOAA issues its first forecast in late May. Additionally, little
predictability is available for knowing the genesis locations and
preferred tracks of hurricanes on a seasonal basis. Continued efforts
are needed into the physics of what determines overall tropical cyclone
activity on interannual timescales, including genesis and track
preferences as well as more skillful statistical and numerical model
guidance.

Variability of tropical cyclones on long (25-40 years) timescales has
been thoroughly documented to occur in the Atlantic since at least the
last couple of decades. During the last century, Atlantic tropical
cyclone activity---especially the major hurricanes---tends to be in
active and quiet phases for about 25-40 years each. Active periods were
observed during the 1870s to early 1900s, the late 1920s to the late
1960s, and most recently from 1995 onward. Conversely, quiet episodes
have been noted from the mid-1900s until the mid-1920s and again from
about 1970 until the mid-1990s. These active and quiet periods are
driven by combined ocean-atmosphere changes, with warm SSTs/reduced
vertical shear and cool SSTs/increased vertical shear occurring in
active and quiet periods, respectively.

Recently, there have been studies that suggest that the Atlantic
activity in the last decade has been unprecedented compared with past
active eras and that such changes are linked to increased SSTs that may
be caused by anthropogenic global warming. Moreover, even the
longer-term swings in activity have also been suggested to have man-made
origins. Such conclusions are currently quite controversial and depend
in part upon the reliability of earlier historic hurricane databases.
Additionally, direct attribution of hurricane activity changes to global
warming causes is problematic as theoretical and numerical modeling
research suggests small increases in hurricane intensity in the future
and rather minor alterations today. (This means that either the
theory/numerical modeling are incorrect, the trend in the databases is
wrong, or that both results need modification). Much research is needed
to ascertain both how much impact global warming is having today and in
the future and how much longer the current active era will last. Efforts
into coupled climate modeling, theoretical climate change studies,
observational work on multidecadal timescales, and reanalyses of
existing tropical cyclone databases are urgently needed to address the
inconsistencies and controversies in this field.

## 5.3 Research Needs in the Social Sciences

As outlined in section 2.8.7, NOAA and other agencies are experiencing
cultural shifts as they recognize the importance of social science to
their mission. There is a growing understanding of hurricane disasters
as social phenomena---intersections of atmosphere, human populations,
social institutions, and the built environment---and that the tools and
methods of the social sciences are essential to mitigating the impacts.
Coastal population growth and land development have resulted in a
dramatic rise in the assets at stake, as well as the value of an
effective response system. Since annual U.S. hurricane losses average
about \$5 billion, a cost savings of \$50 million would result from
every 1 percent of those losses that might be prevented. Knowledge gains
in the social, economic, and decision sciences will lead to the
implementation of better response strategies, and can help set
priorities as to where increased research would be most beneficial.

The next four subsections discuss four areas of social science research
of particular importance to the hurricane forecast and warning system.
Appendix P lists representative research questions in each of the four
areas.

### 5.3.1 Warning Process

Accurate forecasts are effective only if they result in appropriate
actions at every level of response. It is important to understand how
various end-user groups interpret forecasts and warnings and weigh their
level of risk. The utility of products, such as the Saffir-Simpson
hurricane scale, should be evaluated for effectiveness in predicting
risk and impact. Warning terminology and graphics need to be tested for
effectiveness with different segments of the population. What was once
perceived as a simple linear warning communications process has become
more complex with the development of new technologies and new
intermediaries. NWS warnings are interpreted and even tailored for the
individual needs of end users by broadcast media, private entrepreneurs,
and public officials. They can be received via Personal Data Assistants
(PDA), cell phones, and the Internet. Social science research can answer
questions regarding how these new communication processes and mediums
affect hurricane response.

Effective risk communication requires an understanding of how people
interpret and react to various levels and types of danger. Hurricane
forecasts carry a level of uncertainty and more research is needed to
better understand effective ways of communicating probabilities.

Hurricane resiliency, whether at the household or community level, is
largely a product of social and economic resources. Understanding how
issues of race, gender, and class tend to increase the vulnerability of
certain segments of the population is an important step toward tailoring
the content and delivery of warning messages to target high-risk groups.

### 5.3.2 Decision Making

Understanding how different stakeholder groups utilize forecast and
warning messages to make decisions is a social science challenge. It
requires understanding how various terminologies and graphics are
interpreted, as well as the process by which they are turned into
recommendations and actions at various levels and spheres of response.
Official response to warnings is inherently a political process that the
forecast community can best navigate if it understands how issues of
power and authority play out in its jurisdiction. It is important to
understand the role of formal and informal social networks at all levels
of hurricane response.

Severe weather warnings have to be clear not only in terms of the type
of weather that the public and the authorities should prepare for, but
also how likely it is that it will occur. How to convey forecast
uncertainty is an important topic for social science research. A major
problem when issuing severe weather warnings is that the probability of
the most extreme events occurring is very low. Social science research
can lead to a better understanding of how people react to warnings about
low probability, high-impact events. Most people respond to hurricane
warnings as members of families and households. Research efforts to
model household decision making, especially related to evacuation, are
promising and should be expanded.

### 5.3.3 Behavioral Response

The social sciences are making important contributions toward
understanding and modeling hurricane response, including evacuation.
Many factors influence household response, including:

-   Whether the message was received and understood.

-   The level of confidence or trust in the source.

-   Their assessment of risk.

-   The feasibility of various responses given their circumstances.

-   The extent to which the message is confirmed by other sources and
    social networks.

-   The resources available to facilitate their response.

The first step toward promoting effective response is to better
understand this process. Post-event behavioral studies provide important
data in this regard; however, there is a paucity of comparative studies
across events. Protocols need to be developed to promote data sharing
and multi-event, long-term research.

### 5.3.4 Social Impacts and Valuations

The NWS is increasingly asked to quantify the value of improved
forecasts. Conventional cost-benefit analysis, however, fails to account
for the social or human costs incurred when hurricanes impact
communities and families. Qualitative social science research methods
can make important contributions toward documenting impacts not readily
measured by standard economic techniques. Recovery from major hurricanes
usually takes many years and support for multiyear research projects is
important in order to understand long-term impacts. Spatial analysis,
using GIS, is crucial to understanding and assessing impacts on various
segments of the community, including where the homes of high-risk
segments tend to cluster.

### 5.3.5 Social Sciences Summary

The theories, tools, and methodologies of social sciences are crucial to
the enterprise of improving hurricane response. Surveys, focus groups,
in-depth interviews, field observations, and demographic analysis are
some of the methods that can lead to a better understanding of how
forecasts and warnings are received, interpreted, and used. **While
there is a growing recognition of the potential contributions of social
science research, to date it remains underfunded and underutilized.**

## 5.4 Oversight of the R&D Program for Tropical Cyclones

The preceding sections of this chapter, along with appendix P, have
detailed the R&D priorities to further improve the effectiveness of
tropical cyclone forecast and warning services, with the goal of
preventing loss of life and injuries associated with tropical cyclones
and to reduce the Nation's vulnerability to these potentially
devastating storms.

The research priorities, coupled with the transition of research to
operations processes outlined in 4.5, are important to a successful
overarching R&D program for tropical cyclones. Another element that is
vital to the tropical cyclone R&D program is a formal, multiagency,
coordination entity to:

-   Monitor and update a listing of the operational needs of the
    tropical cyclone forecast and warning centers.

-   Monitor and update a listing of the research priorities to meet the
    needs of the operational tropical cyclone forecast and warning
    centers.

-   Develop a succinct 5-year, multiagency research implementation plan
    that outlines specific strategies to address all of the research
    priorities.

-   Update the implementation plan (above bullet) as required (e.g., at
    least annually).

The JAG/TCR recommends that this coordination requirement and
development of a research implementation plan be satisfied **through the
OFCM infrastructure.** One possible solution is to form a Working Group
for Tropical Cyclone Research, co-chaired by NOAA, NASA, NSF, and the
U.S. Navy---with the working group tasked to maintain/publish the above
identified items and, at a minimum, provide updates at the annual
OFCM-sponsored Interdepartmental Hurricane Conference.

## 5.5 Summary

This chapter introduced the operational needs of the tropical cyclone
forecast and warning centers, and drove home the point that meeting the
operational needs will require continued advances in observations, data
assimilation technologies, and tropical cyclone NWP models. Key to these
advances is the Nations commitment to provide sufficient human and
infrastructure resources for tropical cyclone research, development, and
transition of research to operations activities, along with sufficient
resources for the operational NWP model environment. Through these
mechanisms and commitments, operational tropical cyclone forecasting
skill will increase, which will lead to reduced loss of life, injuries,
and vulnerability to tropical cyclones. The next chapter discusses the
tropical cyclone research priorities.