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**Agenda**

**Northeast Regional Operational Workshop X**

**Albany, New York**

**Wednesday, November 5, 2008**

**9:00 am**

**Welcoming Remarks**

Eugene P. Auciello, Meteorologist In Charge

Warren R. Snyder, Science & Operations Officer

National Weather Service, Albany, New York

**Session A -- Cool Season Topics / Winter Weather**

**Session Chair -- Joseph P. Villani**

**9:05 am**

**The Inland Extent of Lake Effect Snow Bands in Central and Eastern New
York**

Joseph P. Villani

NOAA/National Weather Forecast Office, Albany, New York

**9:25 am**

**The 8-9 March 2008 Winter Storm in Upstate New York: An Example of a
"Multi-Hazard" Event**

Brian J. Frugis

NOAA/National Weather Service Forecast Office, Albany, New York

**9:45 am**

**A Further Investigation of Mohawk Hudson Convergence Cases**

Hugh W. Johnson IV

NOAA/National Weather Service Forecast Office, Albany, New York

**10:05 am**

**Intense Surface Cyclone Activity in the Arctic during the 2005--06 and
2006--07 Cool Seasons**

Brian Silviotti

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

**10:25 am**

**Strong Polar Anticyclone Activity over the Northern Hemisphere and an
Examination of the Alaskan Anticyclone**

Justin E. Jones

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

**10:45 am**

**Break**

Beverages & Snacks for sale in Rotunda by Capital District Chapter of
the AMS

**Session B -- Ensemble Forecasting and Modeling**

**Session Chair -- Warren R. Snyder**

**11:10 am**

**Operational High Resolution Modeling for the Vancouver 2010 Olympics**

R. McTaggart-Cowan

Numerical Weather Prediction Research Division, Meteorological Service
of Canada, Quebec, Canada

**11:30 am**

**Customization of a Mesoscale Numerical Weather Prediction System for**

**Industrial Site Operations Applications**

Anthony P. Praino

IBM Thomas J. Watson Research Center, Yorktown Heights, New York

**11:50 am**

**Using Short Range Ensemble Forecasts and High Resolution Model Output
to Assess the Potential for Tornadoes across Southeast Virginia on 28
April 2008**

Josh Korotky

NOAA/National Weather Service Forecast Office, Pittsburgh, Pennsylvania

**12:10 pm**

**Validation of Storm Surge Models for the New York Bight and Long
Island Regions and the Impact of Ensembles**

Tom Di Liberto

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

**12:30 pm**

**Lunch**

**2:00 pm**

**Use of Mesoscale Ensemble Weather Predictions to Improve Short-Term
Precipitation and Hydrological Forecasts**

Michael Erickson

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

**2:20 pm**

**Northeast Regional Ensemble Simulations of the**

10 February 2008 Lake Effect Snow Event: WRF Wind Biases and their
Implications on Forecasted Snow Band Position

Justin Arnott

NOAA/National Weather Forecast Office, Binghamton, New York

**2:40 pm**

**The Ambrose Jet: Climatology and Simulations of Warm-Season Coastally
Enhanced Winds in the New York Bight Region**

Brian A. Colle

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

**3:00 pm**

**Verification of SREF Aviation Forecasts at Binghamton, NY**

Justin Arnott

NOAA/National Weather Forecast Office, Binghamton, New York

**3:20 pm**

**Break**

Beverages & Snacks for sale in Rotunda by Capital District Chapter of
the AMS

**Session C -- General Session and Keynote Presentation**

**Session Chair -- Neil A. Stuart**

**3:50 pm**

**Societal Impacts of Severe Weather -- The Future of Prediction,
Communication and Post-Event Analysis**

Neil A. Stuart

NOAA/National Weather Service Forecast Office, Albany, New York

**4:10 pm**

**A New Hampshire Ground-Level Ozone Pollution Forecasting Tool Using
Meteorological Criteria**

Laura L. Landry

Department of Atmospheric Science and Chemistry, Plymouth State
University, Plymouth, New Hampshire

**4:30 pm**

**Keynote Presentation**

Introduction -- Lance Bosart

**The Explicit Prediction of Convective Storms: Progress and Pitfalls**

Morris Weisman

National Center for Atmospheric Research, Mesoscale and Microscale
Meteorology Division, Boulder, Colorado

**6:00 pm**

**ADJOURN**

**Agenda**

**Northeast Regional Operational Workshop X**

**Albany, New York**

**Thursday, November 6, 2008**

**Session C -- General Session (Continued)**

**Session Chair -- Neil A. Stuart**

**8:30 am**

**2007-8 Verification of the HPC Winter Weather Desk and Upcoming
Changes to the National Centers for Environmental Prediction Short Range
Ensemble Forecast System**

Dan Petersen\
NWS/NCEP Hydrometeorological Prediction Center, Camp Springs, Maryland

**8:50 am**

**A Project to Improve Forecasts of Radiation Fog at Elmira, New York**

Michael L. Jurewicz, Sr.

NOAA/National Weather Service Forecast Office, Binghamton, New York

**9:10 am**

**Integration of a Mesoscale Ensemble System into National Weather
Service Hydro-Meteorological Operations**

Jeffrey Tongue

NOAA/National Weather Service Forecast Office, Upton, New York

**9:30 am**

**A Distributed Flash Flood Forecasting Rainfall-Runoff Model Applied to
Watersheds in the Northeast United States**

Michael Schaffner

NOAA/National Weather Service Forecast Office, Binghamton, New York

**9:50 am**

**Break**

Beverages & Snacks for sale in Rotunda by Capital District Chapter of
the AMS

**Session D -- Warm Season / Convection**

**Session Chair -- Steve R. DiRienzo**

**10:10am**

**Severe Squall Line Across Quebec on August 18th 2008**

**An Overview**

Robert Michaud

Quebec Storm Prediction Centre, Meteorological Service of Canada,
Environment Canada, Montreal, Quebec

**10:30 am**

**Radar Characteristics of the July 2008 New Hampshire Tornado:
Precursor and Tornadogenesis Stages**

John Cannon

NOAA/National Weather Service Forecast Office, Gray, Maine

**10:50 am**

**The Mesoscale Environment Associated with the Formation and
Maintenance**

**of the 24 July 08 New Hampshire Tornado**

Mike Cempa

NOAA/National Weather Service Forecast Office, Gray, Maine

**11:10 am**

**A Spatial Climatology of Convection in the Northeast U.S.**

John Murray

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

**11:30 am**

**Convective System Morphology over Northeast United States**

Kelly Lombardo

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

**11:50 am**

**Preferred Regions of Convective Development over Northern New England
as a Function of Flow Regime: Southwesterly Flow Case Studies**

Jennifer Q. Belge

Department of Atmospheric Science and Chemistry Plymouth State
University, Plymouth, New Hampshire

**12:10 pm**

**Maintenance of a Mesoscale Convective System over Lake Michigan**

Nicholas D. Metz

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

**12:30 pm**

**Lunch**

**Session E -- CSTAR Projects, and Related Topics**

**Session Chair - Tomas A. Wasula**

**2:00 pm**

**A Storm-Scale Analysis of the 16 June 2008 Significant Severe Weather
Event Across New York and Western New England**

Thomas A. Wasula

NOAA/National Weather Service Forecast Office, Albany, New York

**2:20 pm**

**A Diagnostic Analysis of a Difficult-to-Forecast Cutoff Cyclone from
the 2008 Warm Season**

Matthew A. Scalora

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

**2:40 pm**

**A High-Resolution Climatology and Composite Study of Mesoscale Band
Evolution within Northeast U.S. Cyclones**

David R. Novak

NOAA/NWS Eastern Region Headquarters, Scientific Services Division,
Bohemia, New York

**3:00 pm**

**The 2008 "PRE-Season" In Review: A Comparison of Tropical Cyclones
Fay, Hanna, and Ike with Regards to Predecessor Rainfall Event (PRE)
Development**

Michael L. Jurewicz, Sr.

NOAA/National Weather Service Forecast Office, Binghamton, New York

**3:20 pm**

**Break**

Beverages & Snacks for sale in Rotunda by Capital District Chapter of
the AMS

**3:40 pm**

**Use of the Nondivergent Wind for Diagnosing Banded Precipitation
Systems**

Thomas J. Galarneau, Jr.

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

**4:00 pm**

**A Climatology of High Lapse Rates and Associated Synoptic-Scale Flow
Patterns over North America and the Northeast US**

Jason M. Cordeira

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

**4:20 pm**

**Here a TC, There a TC, Everywhere a TC: The \"Spin\" on the Active
Part of the North Atlantic 2008 TC Season**

Lance F. Bosart

Department of Earth and Atmospheric Sciences , University at Albany,
State University of New York, Albany, New York

**5:00 pm**

**ADJOURN**

**6:30pm**

**CSTAR Dinner at Buca di Beppo Italian Restaurant**

**44 Wolf Road, Colonie, New York**

**The Inland Extent of Lake Effect Snow Bands in Central and Eastern New
York**

Joseph P. Villani

NOAA/NWS Weather Forecast Office, Albany, New York

Michael L. Jurewicz

NOAA/NWS Weather Forecast Office, Binghamton, New York

Determining the inland extent of significant lake effect snow bands is
an operational forecasting challenge that impacts the Albany and
Binghamton Weather Forecast Offices' County Warning Areas (CWA) several
times each winter season. Assuming conditions are favorable for
significant lake effect snow bands to exist upstream near the shore of
Lake Ontario, determining how far inland the snow bands will extend is
critical for forecasters. Occasionally, just a few miles can make a
significant difference for a location receiving warning criteria snow
(greater than 18 cm in 12 hours) or very little snow accumulation.

While extensive research has addressed pattern recognition, anticipated
band intensity, and the persistence of lake effect snow, very little
research has addressed the physical mechanisms that modulate the inland
extent of these significant snow bands. The goal of this study is to
determine the primary factors that influence the inland extent of lake
effect snow bands in the Albany and Binghamton CWAs, especially when
significant snow bands are present upstream. Significant lake effect
snow events and null events that have affected the Albany and Binghamton
CWAs during the past several winter seasons are being compiled. These
events will be analyzed in depth utilizing carefully selected parameters
to ascertain the most important factors that modulate inland extent of
lake effect snow events. Parameters to be examined include, but are not
limited to: mixed layer wind direction and speed, low level convergence,
ambient moisture, snow band width, instability class, height of
subsidence inversion, and magnitude of vertical wind shear (both speed
and directional).

Since this project is in the early stages of development, just one case
study from this past winter (20-21 Jan 2008) has been examined using the
aforementioned parameters, and will be discussed in this presentation.
The 20-21 Jan 2008 case was a two-day event, in which 30 to 91 cm of
snow fell in Oswego County, while only 8 to 20 cm fell across portions
of southern Herkimer County. This was a null event in terms of inland
extent for the Mohawk Valley region of East-Central New York. Since this
was a long-duration case lasting 48 hours, the developed parameters will
be investigated throughout the evolution of the event.

Future work will focus on comparing and contrasting several events, in
the hopes that conclusions that will ultimately assist the forecaster in
recognizing the inland extent of lake effect snow will be developed.

**The 8-9 March 2008 Winter Storm in Upstate New York: An Example of a
"Multi-Hazard" Event**

Brian J. Frugis

NOAA/NWS, Weather Service Forecast Office, Albany, New York

The 8-9 March 2008 event was one of the more unique storms to affect the
upstate New York (NY) region during the 2007-08 winter season. Aside
from the typical winter hazards of snow and ice, this particular storm
also brought widespread flooding, strong winds and severe thunderstorms.
The unusual combination of unseasonable severe thunderstorms along with
wind, rain, snow and ice made this an excellent example of a
"multi-hazard" winter event.

The storm track of the 8-9 March 2008 event made the upstate New York
region very susceptible to multiple weather hazards. An 988 hPa center
traveled across the eastern Catskills and Capital Region and brought
warm, moist air to the eastern side of the system. This allowed dewpoint
temperatures to exceed 10°C across the mid-Hudson Valley, southern
Taconics and nearby adjacent portions of western New England. The
abundant low-level moisture and weak instability fueled a rare line of
low-topped thunderstorms, which produced damaging wind gusts. Meanwhile,
a crippling ice storm occurred as sub-freezing air was in place at the
surface across the southern Adirondacks and moisture driven by the storm
over this layer produced an extended period of freezing rain. In between
these two extreme hazards, heavy rainfall, combined with a frozen
ground, several days of snow melt and runoff from a previous heavy rain
event, caused widespread flooding across much of the eastern Catskills
and Greater Capital Region.

This presentation will focus on the factors that led to this particular
storm causing such diverse and unique hazards at the same time across
upstate New York. In addition, the presentation will examine previous
research regarding cool season severe thunderstorm outbreaks to find any
common links between this event and past storms across the upstate New
York region. Geostationary Operational Environmental Satellite (GOES)
data, radar data from the Albany (KENX) Radar, as well as observational
mesoscale data (ie. Local Analysis and Prediction System and Mesoscale
Analysis and Prediction System) from the Advanced Weather Interactive
Processing System (AWIPS) computer system will be used for analysis.

> **A Further Investigation of Mohawk Hudson Convergence Cases**

Hugh W. Johnson IV

NOAA/NWS, Weather Service Forecast Office, Albany, New York

The meteorological phenomena, known as the Mohawk Hudson Convergence
(MHC) has been researched and documented by Mike Augustyniak and others.
These occur when a storm center moves to the east or south of the
Capital District (located at the apex of the Mohawk and Hudson Valleys),
and produces a period of light precipitation in the wake of the main
warm and cold conveyor belts of the departing storm. These events are
generally not associated with lake effect precipitation, although on
occasion it has enhanced them. MHC events usually do not contribute much
to the total storm snowfall. However, a correctly forecasted event
greatly reduces their impact as persistent light snow prolongs IFR
conditions and hampers High Crews.

Augustyniak specifically studied MHC events during the cold season,
namely those tied to snowstorms. A Forecast Decision Tree has been
devised to assist forecasters to determine when and if MHC would occur.

More research is needed on this topic. Can a MHC event happen during the
"warm" season, when low pressure moves to our south and east? Can MHC
happen during times of southerly flow in the Hudson Valley and a
southwest or west wind in the Mohawk Valley? In this situation, MHC
might actually be a focus for convective initiation. Last but not least,
"null" cases should be investigated to better define (if necessary)
Augustyniak's Preliminary Flow Chart.

Several MHC cases will presented, including a Classic, Null, Hybrid,
Warm, and one in "Southerly" Flow regime.

**Intense Surface Cyclone Activity in the Arctic during the 2005--06 and
2006--07 Cool Seasons**

Brian Silviotti, Lance F. Bosart, and Daniel Keyser

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

It is well known that the arctic can be a source of stormy weather,
especially in the winter, with powerful cyclones frequently roaming
about the northern oceans. These cyclones can produce hurricane-force
winds and pose severe hazards, especially to the shipping industry. The
goal of this study is to understand the nature of these strong
cool-season arctic-based storms and how they interact with the middle
latitudes. A manual analysis of the large-scale spatial and temporal
distribution of intense arctic surface cyclones occurring during the
2005--06 and 2006--07 cool seasons is examined. To qualify for inclusion
in the analysis, these surface cyclones had to form during the cool
season (October through March), originate in the arctic (poleward of
50°N), and had to attain a minimum central mean sea level pressure
(MSLP) of at least 980 hPa. A given cyclone in the dataset could have
attained a 980 hPa or lower MSLP reading either by itself (nonmerger) or
by merging with one or more surface cyclones, which can be of arctic or
midlatitude origin, in such a way that only one distinct cyclone can be
seen on an MSLP map (merger).

The 0.5° GFS surface analyses were used to construct the cyclone
dataset. The surface cyclones were subjectively tracked and their
intensity estimated based on MSLP maps. A storm-track climatology was
generated and compared with the large-scale arctic flow for each cool
season. Mergers and nonmergers were compared in regard to track and
intensity of the storms. A brief, representative case study of one such
merger event was performed using an "Eady model" perspective to obtain a
more detailed look at cyclone interaction.

Results of the subjective analysis reveal 145 intense arctic surface
cyclones occurring over both cool seasons. There is high intraseasonal
and interannual variability with 50 cyclones analyzed in the 2005--06
cool season, which was characterized by a mainly negative Arctic
Oscillation/North Atlantic Oscillation (AO/NAO) pattern, and 95 cyclones
analyzed in the 2006--07 cool season, which was characterized by a
mainly positive AO/NAO pattern. There is relatively little spatial
variability within and between the two cool seasons with clear track
clustering in the North Atlantic and East Arctic Oceans. Approximately
27 percent of the cyclones in the dataset are mergers and show similar
geographical distributions as nonmergers. Cyclones resulting from a
merger event attained a mean minimum MSLP value statistically
significantly lower than that of cyclones that did not merge. The
representative case study of a merger event shows two surface cyclones
and three upper-level disturbances (positive potential vorticity
anomalies) merging over the North Atlantic Ocean southeast of Greenland
to form one intense cyclone that deepened 53 hPa in 24 h and attained a
minimum MSLP value of 928 hPa.

**Strong Polar Anticyclone Activity over the Northern Hemisphere**

**and an Examination of the Alaskan Anticyclone**

Justin E. Jones, Lance F. Bosart, and Daniel Keyser

Department of Earth and Atmospheric Sciences, University at Albany,

State University of New York, Albany, New York

Strong polar anticyclones (PAs) have a significant impact on the
cool-season climate over high-latitude landmasses as they are typically
accompanied by arctic airmasses. There is anecdotal evidence the number
of strong PAs, defined by a mean sea level pressure (MSLP) threshold of
1050 hPa, has been decreasing in recent decades. The purpose of this
study is to investigate the change in frequency of occurrence of strong
PAs and to provide an overview of the large-scale dynamical and
thermodynamical processes governing their evolution.

The European Centre for Medium-Range Weather Forecasts ERA-40 and
NCEP--NCAR global reanalysis datasets at 2.5° horizontal resolution were
used to construct a Northern Hemisphere climatology of the frequency of
strong PAs using an MSLP threshold of 1050 hPa. At each grid point, a
counter summed the number of times this threshold was met or exceeded
and the total number of counts was contoured objectively. This spatial
climatology was performed at 10 year intervals from 1 January 1948
through 31 December 2007 using the NCEP--NCAR dataset and from 1 January
1958 through 31 December 1997 using the ERA-40 dataset. The results
indicate that there has been a decrease in the maximum PA frequency of
approximately three to four counts per decade.

Individual PA events (22 total) reaching an MSLP of greater than 1050
hPa over an Alaskan subdomain occurring from 1 January 1977 through 31
August 2002 were then composited using the ERA-40 dataset. The composite
was performed at 24 h intervals beginning 48 h prior to the event and
ending 48 h after the initial time, corresponding to the time when each
individual PA event first reached an MSLP of 1050 hPa. The composite was
used to perform an in-depth examination of large-scale dynamical and
thermodynamical aspects relevant to the development of cold-air
outbreaks over North America in association with strong PAs.

**Operational High Resolution Modelling for the Vancouver 2010
Olympics**

R. McTaggart-Cowan

Numerical Weather Prediction Research Division, Meteorological Service
of Canada, Quebec, Canada

Environment Canada is responsible for providing weather forecasts for
the Vancouver 2010 Olympics (January-March 2010) at lead times ranging
from weeks to hours. An important part of the short range prediction
system is guidance from the High Resolution Modelling System (HRMS)
developed at the Numerical Weather Research Division. This model is
designed to run daily to produce high-quality gridded forecasts over
interleaved 15h forecast ranges as a background for the SNOW V10
Research Demonstration Project, the nowcasting RDP for the 2010
Olympics.

The influence of steep terrain surrounding the venues is clearly one of
the greatest challenges associated with numerical modelling in the
Whistler/Vancouver region. This complexity is enhanced by the presence
of the Burrard Inlet, the Strait of Georgia, and the Pacific "data void"
in the vicinity of the forecast region. In order to provide accurate
forecasts in a region so strongly influenced by forcings on the broad
range of scales from cyclones in the Gulf of Alaska, through frontal
windstorms, to terrain-induced flows, the HRMS uses a triply-nested
model grid, with horizontal spacings of 10 km, 2.5 km and 1 km. The
inner nest is shown to be capable of resolving many of the orographic
features in the Whistler/Vancouver area and producing realistic
simulations of channeled and orographically-perturbed flows.

The forecasting requirements for Olympic events make the production of
reliable high-resolution next-day and same-day guidance absolutely
necessary. Different events have different sensible weather tolerances,
which range from 3-5 m/s winds for ski jumping (depending on threshold
level and wind angle to the jumping slope) to 20-50 m visibility for
downhill races. Not only do the organizers of these events ask for
deterministic prediction of these elements, but they require that
forecasts be made hourly for the upcoming 24 h period. In addition to
event thresholds, participants require additional information, including
such non-standard predictions as snow surface temperatures for
cross-country and biathlon events.

This talk will describe the HRMS that will be run operationally at the
Canadian Meteorological Centre during the Vancouver 2010 Olympics, and
will include a description of the lastest modifications implemented to
addrsess specific issues associated with short range prediction in steep
terrain.

**Customization of a Mesoscale Numerical Weather Prediction System for
Industrial Site Operations** **Applications**

Anthony P. Praino and Lloyd A. Treinish

IBM Thomas J. Watson Research Center

Yorktown Heights, New York

There are many commercial and industrial site operations and processes
that are weather sensitive to local conditions in the short-term (3 to
36 hours). In many cases they may reactive and/or suboptimal due to
unavailability of appropriate predicted data at this temporal and
spatial scale. Hence, the optimization that is applied to these
processes to enable proactive efforts utilize either historical weather
data as a predictor of trends or the results of synoptic-scale weather
models. While near-real-time assessment of observations of current
weather conditions may have the appropriate geographic locality, by its
very nature is only directly suitable for reactive response.
Alternatively, mesoscale numerical weather models operating at higher
resolution in space and time with more detailed physics may offer
greater precision and accuracy within a limited geographic region for
problems with short-term weather sensitivity. Such localized predictive
information can be used to improve operational efficiency, reduce
operating cost and environmental impact as well as improve safety.

To address these issues, we build upon our earlier work, in the
implementation of an operational mesoscale modelling capability, dubbed
\"*Deep Thunder*\". The system provides nested 24-hour forecasts for
several geographies including the New York City metropolitan area as
well as New England at 1 -3 km resolution. In particular, the goal is to
provide weather forecasts at a level of precision and fast enough to
address specific business problems. Hence, the focus has been on
high-performance computing, visualization, and automation while
designing, evaluating and optimizing an integrated system that includes
receiving and processing data, modelling, and post-processing analysis
and dissemination. Part of the rationale for this focus is practicality.
Given the time-critical nature of weather-sensitive business decisions,
if the weather prediction can not be completed fast enough, then it has
no value. Such predictive simulations need to be completed at least an
order of magnitude faster than real-time. But rapid computation is
insufficient if the results can not be easily and quickly utilized.
Thus, a variety of customized and integrated products are being
implemented. They range from techniques to enable more effective
analysis to strategies focused on the applications of the forecasts.

The concept behind *Deep Thunder* in this context is clearly to be
complementary to what the National Weather Service (NWS) does and to
leverage their investment in making data, both observations and models,
available. The idea, however, is to have highly focused modelling by
geography and application. Therefore, we will review our particular
architectural approach and implementation as well as the justification
and implications for various design choices. Then we will outline how
this approach enabled customization for problems associated with
industrial site operations as well as discuss the specific
customizations.

**Using Short Range Ensemble Forecasts and High Resolution Model Output
to Assess the Potential for Tornadoes across Southeast Virginia on 28
April 2008**

Josh Korotky

NOAA/NWS Weather Service Forecast Office, Pittsburgh, Pennsylvania

Richard Grumm

NOAA/NWS Weather Service Forecast Office, State College, Pennsylvania

Short Range Ensemble Forecast (SREF) products are used with high
resolution model output to identify the potential for supercells and
tornadoes across southeast Virginia on 28 April 2008. This study will
illustrate that SREF probability forecasts and deterministic high
resolution model output shouldn't be considered as mutually exclusive
approaches to forecasting. Rather, the complementary strengths of both
approaches can lead a forecaster to greater situational awareness for an
event with high impact potential.

The tornado outbreak across southeast Virginia during the late afternoon
of 28 April resulted in 11 tornadoes and multiple injuries, including an
EF3 rated tornado in the city of Suffolk VA. Although clouds ahead of an
advancing cold front were expected to limit destabilization across the
mid-Atlantic region, persistent low-level moisture inflow coupled with
increasing low- to mid-level wind fields provide sufficient vertical
wind shear to increase the potential for tornadic supercells and bowing
line segments along and ahead of a pre-frontal trough.

This study demonstrates a forecast strategy that utilizes SREF
probability forecasts to assess the potential for supercells and
tornadoes, SREF departures from climatology to evaluate the
climatological context of the model forecasts, and high resolution model
output to resolve the mesoscale organization and evolution of deep
convection.

Although this tornado outbreak occurred in southeast Virginia, the
meteorological environment and resulting storm structures are
particularly relevant across the Ohio Valley and northeast United
States.

**Validation of Storm Surge Models for the New York Bight and Long
Island Regions and the Impact of Ensembles**

Tom Di Liberto, Brian A. Colle, and Frank Buonaiuto

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

The Stony Brook Storm Surge (SBSS) group has developed a real-time storm
surge modeling system for the coastal Northeast U.S using the Advanced
Circulation Model for Coastal Ocean Hydrodynamics (ADCIRC) ocean model
(http://stormy.msrc.sunysb.edu). This talk will highlight the
verification of the ADCIRC over the 2007-2008 cool season (Nov -- March)
using several water level gauges around New York City and Long Island.
The results are compared against NOAA\'s Extratropical Storm Surge Model
and Stevens Institute for Technology's surge modeling system for the
same events. The 60-h deterministic ADCIRC run uses hourly surface winds
and sea-level pressures from the Penn State- National Center for
Atmospheric Research (PSU- NCAR) Mesoscale model (MM5) at 12-km grid
spacing. For the 0000 UTC cycle, ADCIRC is also run 48-h using 8
separate ensemble members, including 5 members from the MM5 and 3
members from the Weather Research and Forecasting (WRF-ARW) model. The
MM5/WRF ensemble members include varied initial conditions (different
operational analyses) and different PBL, convective, and microphysical
parameterizations.

During the 2007-2008 cool season, ADCIRC ensemble members had a negative
mean error (bias) of about -0.10 to -0.13 m for the 12-36 h forecast
period at the Battery, while the root-mean square errors (RMSEs) ranged
from 0.17 to 0.20 m. NOAA\'s ET Surge model had similar errors, with a
negative bias of around -0.17 m for 12-36 h and a RMSE of 0.19 m for
12-36 h. The validation of Steven's modeling system will be presented at
the meeting. The ADCIRC ensemble mean for the same station had a -0.12 m
negative bias for 12-36h, but its RMSE was 0.17 m, which is slightly
smaller than most ensemble members. The negative water levels are often
largest for days when there are significant wave heights near the coast,
which suggests the importance of including wave forcing in these surge
models.

This talk will also summarize the storm surge modeling efforts for
Hurricane Gloria (26-28 September 1985) in the New York Metropolitan
Region. There have been no realistic atmospheric and storm surge model
simulations of historic landfalling hurricanes in this urban-coastal
environment. This event provides a good test case for these numerical
models. Gloria resulted in the highest recorded storm surge of \~7 feet
(2.1 m) at the Battery, NY in the last 50 years. The impact of wave
forcing on the storm surge will be discussed as well as how small track
differences resulted in relatively large water level differences at
numerous stations.

**Use of Mesoscale Ensemble Weather Predictions**

**to Improve Short-Term Precipitation and Hydrological Forecasts**

Michael Erickson^1^, Brian A. Colle^1^, Jeffrey Tongue^2^, Alan Cope^3^,
and Joseph Ostrowski^4^

^1^School of Marine and Atmospheric Sciences, Stony Brook University,
State University of New York, Stony Brook, New York

^2^ NOAA/NWS, Weather Service Forecast Office, Upton, New York

^3^ NOAA/NWS, Weather Service Forecast Office, Mt. Holly, New Jersey

^4^ NOAA/NWS, Mid-Atlantic River Forecast Center, State College,
Pennsylvania

This collaborative project focuses on the improvement of short term (\<
48 hour) quantitative precipitation forecasts (QPF) and streamflow
predictions using both ensemble modeling and verification approaches.
The ingestion of ensemble QPF into hydrologic models will hopefully
improve probabilistic streamflow and stage height forecasts within the
WFO and Mid Atlantic River Forecast Center (MARFC). This talk will
describe the ensemble approach, some examples from the system, and
present verification of the short range (0-48hr) QPF from the ensemble.

Currently, Stony Brook University (SBU) is running a 13-member ensemble
down to 12-km grid spacing over the Northeast U.S. using the MM5 (v3.7)
and WRF-ARW (v2.2) mesoscale models. The 7 members of MM5 and 6 members
of WRF use different initial conditions (GFS, NAM, CMC, NOGAPS) mixed
with different physical parameterizations (convective parameterization,
boundary layer, and microphysics). The model output is converted to grib
format, and our collaborative partners pull the hourly ensemble data
back to their respective offices in real-time using LDM for display on
their AWIPS systems. The SBU ensemble can be combined the NCEP SREF and
other models to provide forecasters a multi-model ensemble perspective.
The QPF data from the SBU ensemble is also used in a variety of ensemble
streamflow applications. The Mt. Holly and Upton, NY WFOs use the Site
Specific for the Passaic and Lodi river basins in New Jersey. The MARFC
ingests the river basin averaged SBU ensemble data into their Ensemble
Streamflow Prediction (ESP) system to produce an ensemble of streamflow
responses. This allows for probabilistic analyses of river response to
model derived QPF for a variety of river basins in the mid-Atlantic.
Past cases using the ESP system will be shown for the Passaic.

The SBU ensemble forecasts were verified using Stage IV precipitation
(\~4-km grid spacing) for the 2006 through 2008 warm (May to August) and
cool (December to March) seasons. For the verification, the higher
resolution stage IV data was interpolated to the resolution of the model
grid with the offshore regions neglected. There is unequal performance
in the ensemble members, with the WRF members performing best over the
cool season. Most members exhibited an overprediction of precipitation,
especially during the warm season, but there are variations across the
Northeast U.S. In addition to error and bias analyses, probabilistic
verification will also be presented.

**Northeast Regional Ensemble Simulations of the 10 February 2008 Lake
Effect Snow Event:** **WRF Wind Biases and their Implications on
Forecasted Snow Band Position**

Justin Arnott and Michael Evans

NOAA/NWS Weather Forecast Office, Binghamton, New York

Lake effect snow (LES) bands are characterized by large gradients in
surface sensible weather, with locations experiencing blizzard
conditions often just miles from areas receiving only flurries. For this
reason, accurate forecasts of LES band location are critical to National
Weather Service forecasters in their preparations of advisories and
warnings for heavy snowfall.

Northeast Regional Ensemble (NRE) simulations of the 10 February 2008
LES event indicated that ensemble members utilizing the ARW core of WRF
(WRF-ARW) had a persistent southward bias in the forecast position of
LES bands. This bias unnecessarily increased ensemble spread in the NRE
forecast, adding uncertainty to the warning decision process. This
finding was consistent with previous research from the 2006-2007 winter
season, and with qualitative observations by WFO Binghamton forecasters
for other events during the 2007-2008 winter season.

In this presentation, the reasoning for the LES band position bias will
be examined. It will be shown that WRF-ARW simulations forecasted overly
strong low-level northwesterly winds upwind of the eastern Great Lakes,
with these winds acting to advect LES bands downwind of the eastern
Great Lakes to the south and east. A series of sensitivity simulations,
using the NMM core of WRF, in addition to two unique versions of the
WRF-ARW, will be used to examine the wind bias, and suggest an optimized
configuration for the ARW members of NRE. It is hoped that this
optimized configuration will lead to improved LES forecasts for the
2008-2009 winter season.

**The Ambrose Jet: Climatology and Simulations of Warm-Season Coastally
Enhanced Winds in the New York Bight Region**

Brian A. Colle^1^ and David R. Novak^1,2^

^1^School of Marine and Atmospheric Sciences, Stony Brook University,
State University of New York, Stony Brook, New York,

^2^NOAA/NWS Eastern Region Headquarters, Scientific Services Division,
Bohemia, New York

The coastal regions of New York and New Jersey are often dominated by
sea-breeze circulations during the spring and summer months.
Occasionally these gentle sea breezes become relatively strong southerly
wind events (\> 11 m s^-1^) that may require marine advisories. These
strong winds are best described as a jet, since the winds are spatially
confined to the New Jersey and Long Island coasts (the New York Bight)
and are vertically confined to the boundary layer (\< 300 m). The
Ambrose Light Station (ALSN6), located at the entrance of New York
harbor, often samples this jet. Thus, the winds have been colloquially
called the Ambrose Jet. This study investigates the climatology of
Ambrose Jet events and the processes responsible for their occurrence.

An Ambrose Jet event was defined as the occurrence of southerly
(160--210 degrees) maximum sustained winds (10 m height) exceeding 11 m
s^-1^ at ALSN6. This wind speed threshold is one standard deviation
greater than the mean wind speed at ALSN6 during 1997--2006. The
sustained wind speed maximum must occur between 18 UTC and 03 UTC. To
assure the wind maximum is spatially localized, the sustained wind at
buoy 44025, located about 50 km to the east-southeast of ALSN6, must be
\<85% of the maximum sustained wind at ALSN6. Analysis of wind data
during 1997--2006 revealed 134 Ambrose Jet events. There is a seasonal
maximum in June and July, with a skew towards the spring months,
suggesting that land-sea temperature contrast and the associated local
pressure gradient are important to Ambrose Jet occurrence. The jet
events exhibit a diurnal cycle, with light southwest winds during the
0600--1500 UTC period, backing to south-southeast and strengthening
during the 1500--2100 UTC period. The winds become more southerly and
reach a maximum generally in the 2100--0000 UTC period. The mean maximum
intensity was 12.5 m s^-1^. After the peak intensity, the winds veer to
a southwest direction as they weaken. The veering winds after 1500 UTC
suggests the influence of the Coriolis force. A composite analysis shows
that the Ambrose Jet is favored on relatively warm days within
synoptic-scale southwest flow on the western flank of the Bermuda high.

An Ambrose Jet event on 2 June 2007 was realistically simulated down to
1.33-km grid spacing using the Weather Research and Forecasting (WRF)
and Penn State--NCAR Mesoscale Models (MM5). Model sensitivity
experiments were conducted to identify how aspects of the complex
coastline curvature of New York Bight and the urban land characteristics
of New York City modify the local pressure gradient and regulate the
Ambrose Jet.

**Verification of SREF Aviation Forecasts at Binghamton, New York**

Justin Arnott

NOAA/NWS Weather Forecast Office, Binghamton, New York

Ensembles are gaining increasing popularity in the forecast process,
playing a large role in our development of extended range forecasts, and
an ever-increasing role in shorter-term, high impact forecasts.
Additionally, in recent years, the resolution of some ensemble forecast
systems has reached the mesoscale, making probabilistic forecasts of
more localized events possible. A natural question is whether aviation
forecasts (i.e. ceiling/visibility forecasts), known for being highly
localized, can benefit from the use of ensemble forecast guidance.

In this presentation, ceiling and visibility forecasts from the Short
Range Ensemble Forecast system (SREF) will be verified for one terminal
aerodrome forecast (TAF) site, Binghamton, NY, for a portion of the 2008
warm season. This study marks the first such verification attempt across
the lower 48 states. Mean forecast values, in addition to various
probability thresholds are examined. It will be shown that while the
SREF forecasts are overly pessimistic in anticipating MVFR/IFR ceilings,
and have difficulty identifying visibility restrictions, there are
instances where this set of guidance performs similarly to more widely
used, deterministic guidance, namely model output statistics (MOS).
Because this study was performed during the warm season, a time
notorious for more challenging MVFR/IFR forecasts, it is suggested that
SREF aviation forecasts may demonstrate increasing skill and usefulness
heading into the 2008-2009 cool season.

**Societal Impacts of Severe Weather -- The Future of Prediction,
Communication and Post-Event Analysis**

Neil A. Stuart

NOAA/NWS Weather Service Forecast Office, Albany, New York

Weather and climate information affects nearly one-third of the U.S.
Gross Domestic Product and influences the decisions of a myriad of users
around the world, including but not limited to the general public,
emergency managers, utility companies and the shipping, aviation,
agriculture and transportation industries. During recent years, there
has been an emphasis within the meteorological community to promote the
development and use of probabilistic forecast products to provide
crucial information on forecast uncertainty resulting in improved
decision making among user groups. Better decisions from all users can
result in minimization of economic impact and loss of life.

Weather-related disasters such as Hurricane Katrina in 2005, the
northeastern U.S. snow event of 13 December 2007 and tornado outbreaks
such as the Super Tuesday 2008 outbreak highlighted the need to
collaborate with social scientists to address vulnerability and
behavioral factors that contributed to the significant economic impact
and death toll in these and similar recent events. Many of the
probabilistic forecast products that are being developed are the result
of multi-sector collaborations, and incorporates social science research
for increased consideration of user needs.

Several examples of products and services will be shown that are under
development within the National Weather Service and the Hazardous
Weather Test Bed. These potential future products and services will
address societal impacts and forecast uncertainty with regard to severe
weather hazards such as winter storms, severe thunderstorms and
tornadoes. An experimental winter weather impact scale will be presented
that can guide forecast staff to address different societal impacts in
winter weather warning products. Probabilistic severe thunderstorm and
tornado warnings will be compared to the current warning polygon
paradigm.

Examples of potential usage of the new products and services will be
presented using recent winter storm and severe weather events,
specifically the Valentine's Day 2007 snowstorm and the 24 July 2008 EF2
tornado in New Hampshire and Maine. Current and future formal
verification techniques will be discussed as well.

**A New Hampshire Ground-Level Ozone Pollution Forecasting Tool Using
Meteorological Criteria**

Laura L. Landry

Department of Atmospheric Science and Chemistry

Plymouth State University, Plymouth, New Hampshire

For over 15 years, New Hampshire Department of Environmental Services
(NHDES) has forecasted ground-level ozone conditions. In March 2008, the
Environmental Protection Agency (EPA) implemented a new National Ambient
Air Quality Standard for the 8-hour average ozone concentration,
lowering it from 84ppb to 75ppb. A forecasting tool was developed to
provide guidance for NHDES air quality forecasters predicting
exceedances of the new standard. Select New Hampshire air monitoring
sites were investigated with datasets consisting of meteorological and
air quality monitoring data for 2002-2007. The data were analyzed for
relationships between meteorological parameters and ozone concentration
at each station to define threshold values beyond which exceedances are
probable. Meteorological parameters chosen to study were daily maximum
surface temperature, 850hPa temperature at 1200UTC, and 1200UTC and
1800UTC surface wind speed, surface wind direction, and cloud cover for
June-August. Criteria values were established by subjectively
determining a threshold value above (such as with 850hPa temperature) or
below (such as with wind speed) which most maximum daily ozone
concentrations exceeded 75ppb.

The final product is presented in a tabular format with each variable's
threshold value per station. While there were a few differences, in most
cases every station resulted in similar threshold values for 75ppb. In
general, an exceedance day is most likely to occur within the study area
when the following conditions occur: daily maximum surface temperature
of about 83˚F or higher, 850hPa temperature at 1200UTC of approximately
12˚C or greater, surface wind speeds at 1200UTC of 5 kts or less,
southwesterly to southerly surface wind direction at 1200UTC, cloud
cover at 1200UTC of 25% or less, surface wind speeds at 1800UTC of
approximately 10 kts or less, westerly to southwesterly surface wind
direction at 1800UTC, and cloud cover at 1800UTC of 50% less. These
results are consistent with meteorological conditions known to promote
ozone production. Overall for each station, threshold values do not seem
to vary significantly regardless of the number of years used to
determine them. The results from this project will be used as an
additional operational tool by NHDES air quality forecasters in their
daily assessment of ground-level ozone in New Hampshire.

**The Explicit Prediction of Convective Storms: Progress and Pitfalls**

Morris Weisman

National Center for Atmospheric Research, Mesoscale and Microscale
Meteorology Division, Boulder, Colorado

Over the past several spring and summer seasons, 36 h realtime explicit
convective forecasts have been produced for the central US with the
WRFARW model, using a 4 km horizontal grid resolution for 2003-2006 and
3 km in 2007 and 2008. These forecasts suggest significant value added
for such high resolution guidance as compared to coarser resolution
forecasts using convective parameterizations; most notably, in the
realistic representation of convective mode (e.g., squall lines, bow
echoes, supercells, mesoscale convective vortices) as well as in
representing the climatological characteristics of convection, such as
precipitation episodes and the diurnal convective cycle. However, no
improvement in overall guidance can be documented as to the timing and
location of significant convective outbreaks. Perhaps the most notable
result has been the strong correspondence between the coarse resolution
NAM/GFS and WRF-ARW guidance, for both good and bad forecasts,
suggesting the overriding influence of larger-scales of forcing on
convective development in the 24-36h timeframe. In this talk, I will
summarize the key successes and failures we have experienced to date in
this endeavor, and will discuss the implications for the future of
multi-day convective predictions.

**2007-8 Verification of the HPC Winter Weather Desk and Upcoming
Changes to the National Centers for Environmental Prediction Short Range
Ensemble Forecast System**

Dan Petersen\
NWS/NCEP Hydrometeorological Prediction Center, Camp Springs, Maryland

First, verification of HPC's Winter Weather Desk (WWD) forecasts from
the winter of 2007--2008 will be presented, including snowfall, freezing
rain, and low track forecasts. Verification of snow-to-liquid ratio
(SLR) techniques will be shown. Upcoming changes to the National Centers
for Environmental Prediction (NCEP) Short Range

Ensemble Forecast System (SREF) will be shown. The SREF changes will
outline member composition and resolution changes, and the need to
correct for 2 meter low temperature biases in a few of the members. A
case study will be shown comparing how the new SREF performed in a
winter event over the northeast in February 2008 versus how the prior
operational version of the SREF performed.

**A Project to Improve Forecasts of Radiation Fog at Elmira, New York**

Michael L. Jurewicz, Sr.

NOAA/NWS Weather Service Forecast Office, Binghamton, New York

One of the primary missions of the National Weather Service (NWS) is to
support the nation's commerce and transportation industries. As such,
accurate forecasts of conditions which impact aviation operations are
critical.

The Weather Forecast Office in Binghamton, NY (WFO BGM) is responsible
for issuing Terminal Aerodrome Forecasts (TAFs) for six different sites
in Central New York and Northeastern Pennsylvania. One of these airports
is located in Elmira New York (KELM), within the Chemung River Valley,
which is a favored location for radiation fog formation, and thus
frequent episodes of Low Instrument Flight Rules/Instrument Flight Rules
(LIFR/IFR) conditions. This presentation will detail work done at WFO
BGM to improve forecasts of LIFR/IFR conditions associated with
radiation fog at KELM.

Statistics were compiled using observations and archived data from model
soundings associated with the occurrence and non-occurrence of fog at
KELM on nights with clear skies and light winds during a 2 year period
(2001-2002). The study determined that critical parameters that control
the development of radiation fog at KELM include boundary layer wind
speed (above the surface), departures between observed temperature and
the previous day's cross-over temperature (from the "UPS Technique"),
and river/air temperature gradients.

The results from this study are being incorporated into operations by
utilizing a locally developed application that compares current forecast
data to a database of historical radiation fog events. The application
works by identifying historical events that are most similar to current
expected conditions, based on the similarity of the parameters from the
aforementioned study. After the most similar historical events are
identified, the application returns information on these events,
including event minimum visibility, and the duration of associated
LIFR/IFR conditions. This information helps forecasters anticipate
upcoming conditions, based on the assumption that current events will
most likely produce conditions that are similar to their historical
analogues.

**Integration of a Mesoscale Ensemble System into National Weather
Service Hydro-Meteorological Operations**

Jeffrey Tongue, Nancy Furbush, Matthew Sardi

NOAA/NWS Weather Service Forecast Office, Upton, New York

Josh Watson

NOAA/NWS Eastern Region Headquarters, Bohemia, New York

Michael Erickson

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

The National Weather Service (NWS) forecast offices utilize the Advanced
Weather Interactive Processing System (AWIPS) for weather analysis and
forecasting. Data from local numerical weather prediction systems can be
ingested into the system via the Local Data Manager (LDM) software
program within AWIPS. Once the data are ingested into AWIPS, the AWIPS
software must be modified to recognize the data for display and
interrogation. Lastly, forecasters must be trained on data usage and
develop personal methodology to integrate these data into their forecast
process.

Data from the Stony Brook University (SBU) Mesoscale Ensemble System
(MES) has been integrated into the NWS New York City Weather Forecast
Office AWIPS. These data are incorporated into the various applications
within AWIPS including the Site Specific Hydrologic Prediction System
(SSHPS). The SSHPS allows forecasters at the NWS to perform mesoscale
hydrology on small, fast responding basins. The integration of the SBU
MES quantitative precipitation forecast (QPF) data into SSHPS allows for
the evaluation of mesoscale hydrology using mesoscale ensemble QPF for
the first time in an operational environment.

This presentation will demonstrate how the Stony Brook MES data are
integrated into AWIPS, how the data are assimilated by forecasters, and
how SSHPS integrates the data for hydrological predictions.

**A Distributed Flash Flood Forecasting Rainfall-Runoff Model Applied to
Watersheds in the Northeast United States**

Michael Schaffner

NOAA/NWS Weather Service Forecast Office, Binghamton, New York

Carl Unkrich

US Department of Agriculture, Agricultural Research Services, Tucson,
Arizona

Flash floods pose a significant danger to life and property in the
northeast United States. One effective way to mitigate flood risk lies
in implementing a real-time forecast and warning system based on a
rainfall-runoff model. The Kinematic Runoff and Erosion Model
(KINEROS2 - www.tucson.ars.ag.gov/kineros) is a spatially distributed
watershed model driven by high resolution radar rainfall input. In this
study, KINEROS2 was used to evaluate such a system in several watersheds
in New York State.

KINEROS2 provides a temporal and spatial resolution not currently
available with other National Weather Service flash flood forecasting
models. KINEROS2 can run on a user defined time-step. For this study,
the model time-step was set to a 5-minute interval to match input from
the 5 minute Digital Hybrid Reflectivity (DHR) radar product which has a
1-degree by 1-km resolution on average. KINEROS2 can also run ensembles
that allow the forecaster to evaluate various scenarios. The scenarios
may be precipitation based, allowing forecasters to examine the effect
of different Z-R relationships on watershed response. Scenarios can also
be modeled by varying model parameters which allows the forecaster to
examine a range of natural variation in watershed hillslope and channel
characteristics. KINEROS2 can be applied to watersheds with or without
stream gauges.

Results from three watersheds in the Catskill Mountains of Delaware
County will be shown. Both gauged and ungauged watersheds were
evaluated. Model parameter variation, both in saturated hydrologic
conductivity and channel length, was also observed. Parameter variation
was attributed to storm size, duration, and resultant basin averaged
rainfall totals. Model calibration based on these two model parameters
with reference to basin average rainfall produced a robust set of
streamflow ensembles that can be run to predict the timing and magnitude
of the peak flow from flood flows in small, fast-responding watersheds
in complex terrain.

**Severe Squall Line Across Quebec on August 18th 2008**

**An Overview**

Robert Michaud

Quebec Storm Prediction Centre . Meteorological Service of Canada,
Environment Canada, Montreal, Quebec

A severe squall line moved across the province of Quebec on August
18^th^ 2008 causing wind gusts up to 90 km/h with few reports of small
hail (1 to 2 centimetres in diameter) and few reports of funnel clouds
with its passage. This event will be analyzed synoptically and
thermodynamically in order to reveal its classical structure and
behaviour. The Montreal radar (McGill) was not operational during the
past summer for maintenance but the event was depicted by either the
Franktown (near Ottawa) or Villeroy (just southwest of Quebec City). The
radar data used will show the classical nature of the squall line as it
moved across the southern part of the province (convective and
stratiform parts). The data will also show a well defined supercell
ahead of the main squall line which gave challenge to the Severe Weather
forecaster team.

**Radar Characteristics of the July 2008 New Hampshire Tornado:
Precursor and Tornadogenesis Stages**

John Cannon, Dan St. Jean and Mike Cempa

NOAA/NWS Weather Service Forecast Office, Gray, Maine

On 24 July 2008, a long-lived tornado raced across eastern New
Hampshire. The 52 mi (84 km) path was the longest continuous tornado
track ever recorded in New England. This path length eclipsed other well
known historical New England storms such as the Worcester, Great
Barrington and Stockbridge tornadoes. One death occurred and hundreds of
homes were damaged by the rain wrapped EF-2 (Enhanced Fujita) tornado.
Detailed storm track information and storm damage photos can be viewed
at <http://www.erh.noaa.gov/er/gyx/>.

An anomalously vigorous (three standard deviations from the atmospheric
mean), cut-off, upper level low pressure system and strong low level
winds provided favorable dynamics to produce the tornadic storm.
Tornadogenesis occurred despite modest atmospheric instability and
limited cloud to ground lightning. Rather, a series of storm scale
interactions likely enhanced the evolving tornadic cell, which was
evident in radar animations.

High resolution radar products from the National Weather Service
WSR-88Ds in Brookhaven, New York, Taunton, Massachusetts and Gray, Maine
were collected to further examine storm morphology. The imagery revealed
two unique stages to the convective lifecycle of the storm, which will
be defined as a "precursor stage" and a "tornadogenesis stage".

The "precursor stage" was associated with storm scale dynamics that
preceded the development of the tornadic cell. This period was initially
characterized by a pulse of inbound velocities approaching Long Island,
New York early on 24 July. Subtle, but distinct cell mergers occurred as
this storm entered Connecticut. Radar reflectivity images showed this
enhanced convection triggered the formation of a bowing segment which
propagated to the right of the mean atmospheric flow.

During the formative "tornadogenesis stage", the convective cell which
eventually produced the tornado evolved. A circulation formed near the
apex of the bow echo. Rotation increased as the cell intersected the
junction of the Merrimack Valley and surrounding hill towns and
continued to fluctuate as the storm traversed northeast at 40 kts across
complex terrain. A final cell merger was then coincident with the
development of a second bow echo and a rapid increase in low-level
shear. A tornado touchdown soon followed. Radar animations detailing the
storm morphology which produced the long-lived tornado will be
presented. A conceptual diagram will be displayed to demonstrate that
complex and discrete storm scale interactions accompanied the organized
convection and tornadogenesis.

**The Mesoscale Environment Associated with the Formation and
Maintenance of the 24 July 08 New Hampshire Tornado**

Mike Cempa, Dan StJean and John Cannon

NOAA/NWS Weather Service Forecast Office, Gray, Maine

On 24 July 2008, a long lived tornado tracked across eastern New
Hampshire. The 52 nm path from Deerfield to Freedom was the longest
continuous tornado track ever recorded in New England. This path length
exceeded the path length of the previous longest tornado in New England,
the 46 nm Worcester tornado of 1953. One death occurred, while hundreds
of homes and tens of thousands of trees were damaged by the rain-wrapped
Enhanced Fujita Scale (EF-2) tornado. Detailed storm track information
and storm damage photos can be viewed at
<http://www.erh.noaa.gov/er/gyx/>.

An anomalously vigorous (three standard deviations stronger than the
atmospheric mean) upper level low pressure system and associated strong
low level wind fields provided favorable upward vertical motion and
vertical wind shear to support a tornadic storm. Tornadogenesis occurred
despite modest instability parameters for summertime. It will be
proposed that a series of mesoscale interactions likely enhanced the
environment to allow tornadogenesis, and maintenance of the tornado for
approximately 80 minutes.

The tornado developed in an environment that featured above-normal
precipitable water values, with strong lower-tropospheric southerly flow
atop a boundary layer inversion. Significant cloud cover existed across
eastern New England, with relatively stable marine air trapped below the
inversion, yet there was modest elevated instability above the boundary
layer. Storms that formed in this environment prior to the development
of the tornado produced heavy rain but did not transport any of the
strong winds down to the surface.

An area of mid-morning clearing in eastern New Hampshire allowed
sufficient insolation to increase surface based instability.
Additionally, the resulting differential diabatic heating along the
clear-cloud boundary would likely have increased the local wind shear
and horizontal vorticity. A line of weak storms moved into this area and
two cells rapidly developed on this line, resulting in strong winds
aloft mixing down to the surface. Both cells produced damaging winds,
with the northern storm producing the tornado. Some ideas will be
presented as to why the tornado formed with the northern cell, including
the presence of a surface moisture gradient in the area of the tornado
producing storm, enhanced low-level southeast flow just ahead of and
prior to the storm, existing outflow boundaries from previous storms and
the influences of terrain. The importance of these features in
maintaining the tornado along its lengthy track will also be examined.

**A Spatial Climatology of Convection in the Northeast U.S.**

John Murray and Brian A. Colle

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

The goal of this presentation is to highlight the spatial distribution
and evolution of deep convection over the Northeast U.S. during the warm
season (April through September). There is little knowledge of where
convection is initiated over the Northeast U.S. in relation to the
terrain, coastal, and urban areas. It is also not well known how
convection evolves diurnally and as the warm season progresses. A
convective climatology was constructed for the Northeast U.S. using 2km
by 2km resolution NOWrad radar data from 1996-2007 as well
cloud-to-ground lightning from the National Lightning Data Network
(NLDN) from 2001-2007. The lightning counts were interpolated to a 10km
by 10km grid over the Northeast U.S.

The frequency of convection at each grid point over the Northeast U.S.
was obtained by summing every 15-min the composite reflectivity values
that are at least 45 dbZ. There are preferred regions for convection
within the Hudson Valley, western and southeast Pennsylvania, central
New Jersey and into the Delmarva Peninsula. A favored initiation area
includes the immediate lee of the Appalachians. There is a sharp
gradient in convective frequency immediately west of the coast (around
New York City) as a result of the cooler marine boundary layer. As the
warm season progresses, the convective activity shifts more towards the
coast, which is consistent with the warming sea surface temperatures.
During the mid-day period (18-00 UTC), the maximum convection is clearly
over inland areas, but by late at night (06-12 UTC) the convective
maximum shifts more offshore from the southern New England coast
extending southwest across the waters through the vicinity of the
Chesapeake Bay. Composites using the North American Regional Reanalysis
(NARR) will highlight some of the flow patterns attached to the favored
areas of convective development. The various life cycles of convection
over the Northeast are analyzed using Hovmoller plots to highlight
genesis and decay regions.

**Convective System Morphology over Northeast United States**

Kelly Lombardo and Brian A. Colle

School of Marine and Atmospheric Sciences, Stony Brook University, State
University of New York, Stony Brook, New York

Convection organization is often related to the type of severe weather
most likely to occur (tornadoes, straight-line winds, and/or flash
flooding). Previous work has classified the convective structures over
the Central U.S., but a similar study for the Northeast U.S. does not
exist. The ambient environment over the Northeast is much different than
the Plains, typically with less CAPE over the Northeast, as well as
influences by the Appalachian terrain, coastal marine boundary layer,
and major urban metropolitan areas, such as New York City.

The different convective structures over the Northeast were classified
during the 2007 warm season (May -- Sept) using the same approach as
Gallus et al. (2008) over the central U.S. This involved perusing hourly
NOWRAD (2-km grid-spacing) radar imagery and classifying the convection
into five types of cellular convection (long-lived individual cells,
short-lived individual cells, clusters of long-lived cells, clusters of
short-lived pulse cells, and broken squall lines), five types of linear
systems (bow echoes, squall lines with trailing stratiform rain, lines
with leading stratiform rain, lines with parallel stratiform rain, and
lines with no stratiform rain), and nonlinear systems.

Preliminary results suggest a nearly equal frequency of cellular,
nonlinear, and linear events across the Northeast, with multiple types
coexisting simultaneously. This distribution is similar to the upper
Midwest (Gallus et al. 2008). While nonlinear convection and convective
clusters do not have a preferred time of development during the day,
individual cellular events preferentially occur between 1700-1800 UTC.
Similarly, linear systems develop in the late afternoon and early
evening. Typically, cellular archetypes both develop and decay within
the Appalachian high terrain, while there is evidence that linear
systems propagate away from the high terrain.

Though the convective morphologies are similar across the two regions,
the production of severe weather varies significantly in association
with these structures. For example, Northeast hail events are evenly
distributed among convective clusters, nonlinear, and non-stratiform
linear systems. Central U.S. hail develops primarily with broken lines,
bow echos, and parallel stratiform linear systems. This presentation
will further highlight the severe weather associated with each
convective type and the favored large-scale ambient conditions.

**Preferred Regions of Convective Development over Northern New England
as a Function of Flow Regime: Southwesterly Flow Case Studies**

Jennifer Q. Belge and Eric G. Hoffman

Department of Atmospheric Science and Chemistry Plymouth State
University, Plymouth, New Hampshire

Lowery (2008) performed a 5 year (2003-2007) climatology on northern New
England thunderstorms as a function of large-scale flow. This study
examined the spatial distribution of convection relative to the terrain
in the Gray, ME (KGYX) radar and found that for southwesterly flow at
700 hPa, the most significant convective initiation region was located
in central Oxford (ME), central Franklin (ME), and southern Somerset
(ME) counties. Lowery's study did not address the question of why
thunderstorms favor these genesis regions for a particular flow regime.
Therefore this study will attempt to answer this question by looking at
two case studies for southwesterly flow at 700 hPa.

In order to choose case studies, radar reflectivity was examined for
each case indentified by Lowery (2008) from just one season:
May-September 2007. Case studies were selected based on the following
criteria: 1) the thunderstorm cells were observed to initiate in the
areas identified by Lowery (2008); and 2) the thunderstorm cells were
not associated with a frontal zone. The purpose for the 2^nd^ criterion
was that we wanted to analyze the mesoscale interaction between the
terrain and large-scale flow for cell development in these significant
genesis regions, and therefore we wanted to be able to eliminate the
influence from a frontal boundary. This presentation will focus on the
southwesterly flow cases from July 13, 2007 and August 3, 2007.

Each case study will analyze moisture, instability, and lift in the
genesis regions using the LAPS (Local Analysis and Prediction System)
dataset. Results from the July 13, 2007 case show that dew point values
at 1700 UTC, just before convective initiation, were around 55° F and
CAPE values were about 600 J/kg. For the August 3, 2007 case, CAPE
values were about 2500 J/kg with dew points around 65° F. For each case
study, areas with no convective initiation had the same or even a more
sufficient supply of moisture and/or instability. This suggests that
moisture and instability are not the critical factors for determining
the location for convective initiation in the prefrontal environment in
southwesterly flow. When the surface flow field was examined, an area of
convergence was seen in both cases in the vicinity of the genesis
region. Furthermore, a weak surface trough was also observed in this
area. We are hypothesizing that the surface convergence and
corresponding pressure trough could provide the necessary lift for the
convection to initiate in the favored areas identified by Lowery (2008).

**Maintenance of a Mesoscale Convective System over Lake Michigan**

Nicholas D. Metz and Lance F. Bosart

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

Mesoscale convective systems (MCSs) are ubiquitous features across the
upper Midwest during the warm season. MCSs that traverse the Great Lakes
and vicinity during the warm season are of interest because the cooler
lake waters relative to the surrounding land may decrease (increase)
surface-based CAPE (CIN) and result in weakening of the MCSs. However,
some MCSs are observed to maintain their strength, or even intensify, as
they traverse the Great Lakes, suggesting that these MCSs may be feeding
on an accelerated "surface" flow that lies just above a shallow
surface-based stable dome of cold air over the Great Lakes. The purpose
of this presentation will be to explore the dynamical and physical
mechanisms that control the maintenance of a warm-season MCS as it
crosses the Great Lakes.

Around 1100 UTC 7 June, an MCS developed over northwestern Iowa, on the
eastern end of a surface boundary. The cold pool from the MCS acted to
extend this surface boundary into southern Minnesota and Wisconsin as
the MCS progressed eastward. Enhanced shear along and isentropic ascent
over the surface boundary led to additional convective development and
numerous associated tornado, severe wind, and severe hail reports.
Additionally, a large supercell formed as a separate outflow boundary
intersected the MCS cold-pool-induced boundary and produced many tornado
reports near Chicago. As the MCS crossed Lake Michigan, composite radar
reflectivity did not show any weakening and severe wind reports
continued to occur as the eastern extent of the MCS reached western
Michigan.

A detailed examination of the MCS that crossed Lake Michigan on 7--8
June 2008 and the associated MCS cold-pool-induced boundary will be
presented. Our analysis of the 7 June 2008 meteorological environment
shows that the MCS was able to form in a high shear environment. Dry air
around 800-hPa allowed for the formation of a strong and deep surface
cold pool, and the balance between the strong shear and cold pool
promoted vigorous ascent. The depth of the MCS cold pool as the system
approached Lake Michigan was much larger than the depth of the cold dome
over Lake Michigan, allowing for continued ascent over the lake.
Additionally, the MCS crossed Lake Michigan in the presence of intense
frontogenesis along the western Lake Michigan shore and a low-level jet
that advected warm unstable air into the MCS region.

**A Storm-Scale Analysis of the 16 June 2008 Significant Severe Weather
Event Across New York and Western New England**

Thomas A. Wasula

NOAA/NWS Weather Service Forecast Office, Albany, New York

On 16 June 2008, a widespread severe weather event occurred across much
of upstate New York and portions of New England. The Storm Prediction
Center posted a moderate risk that afternoon from the Mohawk River
Valley, Greater Capital Region and southwestern New England southward
into the Mid Atlantic region. The Northeast United States had over 100
severe reports of damaging winds in excess of 50 knots (58 mph), and
large hail (greater than 1.9 cm). There was also one confirmed tornado
in the lower Hudson Valley. The vast majority of the severe reports were
large hail, with a few hail stones exceeding 5.0 cm in diameter. The
severe convection was focused ahead of a surface cold front and a potent
short wave trough rotating around a strong 500 hPa cutoff low,
meandering southeast from Southern Ontario and Lake Superior.

Observational data, as well as short range deterministic and
probabilistic model guidance suggested a major severe weather outbreak
was about to occur. A cyclonically curved upper-level jet was located
southwest of New York with a plume of divergence over the Northeast in
the afternoon. Much of the southern portion of the Albany forecast area
was in the favorable left front quad of a mid-and upper-level jet
streak. The 1800 UTC KALB sounding indicated convective temps would be
in the mid to upper 70s°F, if appreciable surface destabilization
happened ahead of the surface cold front. Surface based convective
available potential energy values of 1000-2000 J kg^-1^ were expected
with steepening mid-level lapse rates to around 7ºC km^-1^, coupled with
wet bulb zero heights falling to 9-10 kft. The bulk shear values in the
0-6 km layer were in the 45-50 kt range, suggesting the possibility of
isolated to scattered supercells. The forecaster thinking for
predominant convective mode this day, however, was for mainly
multi-cellular convection with large hail and damaging winds due to the
steep lapse rates and strong jet dynamics.

This talk will focus on a detailed radar analysis of the event,
utilizing some of the new tools available for operational forecasters
this past warm season. Those tools include the Four -Dimensional
Stormcell Investigator and GR2Analyst software. Traditional base and
derived radar products will also be shown. The storm-scale analysis will
focus on helpful techniques to determine what produced the copious hail
reports.

**A Diagnostic Analysis of a Difficult-to-Forecast Cutoff Cyclone from
the 2008 Warm Season**

Matthew A. Scalora, Lance F. Bosart, and Daniel Keyser

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

Neil A. Stuart and Thomas A. Wasula

NOAA/NWS Weather Service Forecast Office, Albany, New York

Forecasting both heavy precipitation and severe weather associated with
slow-moving 500 hPa cutoff cyclones can be challenging during the warm
season. Models often have trouble predicting the evolution of cutoff
cyclones and forecasting accurate precipitation amounts. Short-wave
troughs and associated vorticity maxima are observed to rotate around
the center of these cyclones. The forecast challenge is to predict the
timing of short-wave troughs and vorticity maxima, along with the
thermodynamic environment these features will encounter. The 2008 warm
season over the Northeast was an active cutoff season. This study takes
a close look at the 22--25 July 2008 cutoff cyclone that was challenging
to forecast.

The 0.5° GFS analyses were used as the basis for the case study. In
addition, climatologies were created using the 6-h 2.5° NCEP--NCAR
reanalysis by computing monthly averaged data for 1992--2007. This
period is felt to be long enough to establish accurate means and
standard deviations. Standardized anomalies of the 0.5° GFS analyses
were computed for parameters such as 700--500 hPa lapse rates, 925--700
hPa wind shear, 850 hPa jet strength, and precipitable water. Other
sources of data used in this study include soundings, radar, and surface
observations. Precipitation plots were created from 6-h analyses
obtained from the NWS National Precipitation Verification Unit.

The 22--25 July 2008 cutoff cyclone developed from a preexisting trough
over eastern Canada. An elongated upstream 500 hPa vorticity lobe and
associated cyclonic vorticity advection contributed significantly to
severe weather, as did surface boundaries and +2 to +3 standard
deviation (SD) 925--700 hPa vertical wind shear. Its +2 to +3 SD
precipitable water anomalies yielded flash flooding and widespread rain
amounts of 7--9 cm. Severe weather on 24 July, including two tornadoes,
was also associated with low-level θ~e~ advection and a +4 to +5 SD 850
hPa jet. These features contributed to the rapid transport of moisture
from the Gulf of Mexico and western North Atlantic and to the
convergence of moisture over the Northeast.

**A High-Resolution Climatology and Composite Study of Mesoscale Band
Evolution within Northeast U.S. Cyclones**

David R. Novak^1,2^, Brian A. Colle^2^ , and Anantha Aiyyer^3^

^1^NOAA/NWS Eastern Region Headquarters, Scientific Services Division,
Bohemia, New York

^2^School of Marine and Atmospheric Sciences, Stony Brook University,
State University of New York, Stony Brook, New York,

^3^Dept. of Marine, Earth and Atmos. Sciences, North Carolina State
University, Raleigh, North Carolina

Intense precipitation bands are frequently observed in the comma-head
sector of extratropical cyclones. Although previous climatologies over
the northeast U.S. have established that these bands are favored during
the development of a closed midlevel low, many cyclones with closed
midlevel lows fail to produce bands. In addition, limited observations
and coarse resolution analyses have prohibited the description of the
mesoscale forcing and stability evolution during band life cycle. This
study utilizes hourly 20-km Rapid Update Cycle analyses and 2-km
composite radar data to explore the mesoscale forcing and stability
evolution during banded events. The study also explores how the
mesoscale forcing and stability evolution differ between cyclones with
closed midlevel circulations that develop bands and those that do not.

Fifty-six heavy precipitation cases with a 700-hPa low over the
northeast U.S. were identified during five cold seasons (Oct--Apr).
Twenty-seven single-banded events were observed in the comma-head in 23
of the heavy precipitation cases (three cases exhibited multiple
events). The remaining 33 cases exhibited a 700-hPa low, but failed to
develop a single band in the comma-head. Nineteen of these 33 cases were
considered pure null events, exhibiting an absence of single-banded or
even transitory banded features. Composites were created for the 27
banded and 19 null events, with analysis focused on the frontogenesis
and stability evolution.

The results reveal a common band life cycle, which is marked by small
conditional stability and increasing frontogenesis during band
formation, and large conditional stability and diminishing frontogenesis
during band dissipation. The composite band develops as forcing for
ascent increases along a mesoscale trough that extends poleward of the
700-hPa low. This trough is a reflection of the development of a
midlevel thermal ridge (the trowal). Band dissipation occurs as
deformation weakens, associated with larger height falls occurring to
the east of the midlevel trough. Many null events also exhibit midlevel
trough formation and associated forcing for ascent; however, the mean
null event frontogenesis was only half the magnitude of the mean banded
event frontogenesis. Banded cyclones are deeper and exhibit a stronger
temperature gradient and deformation maximum than the null cyclones,
resulting in faster growth of frontogenesis. The stability was similar
between composites, highlighting that the primary discriminator between
banded and null events is the strength of the midlevel frontogenesis.
Predictability implications of these results will be presented at the
workshop.

**The 2008 "PRE-Season" In Review: A Comparison of Tropical Cyclones
Fay, Hanna, and Ike with Regards to Predecessor Rainfall Event (PRE)
Development**

Michael L. Jurewicz, Sr.

NOAA/NWS Weather Service Forecast Office, Binghamton, New York

PREs are coherent areas of heavy rainfall that develop in advance of
tropical cyclones (TC). Although rainfall associated with PREs occurs
separately from the main precipitation shields of a TC, there is a
relationship between the PRE and their parent TC. On average, one out of
every three TC that make landfall along the Atlantic or Gulf coastal
regions of the United States has at least one associated PRE.(Cote, et.
al, 2007). Since attention is often focused on regions more directly
affected by the TC, a PRE can create significant runoff problems for
areas where flooding is not initially expected.

This presentation will look at three TCs from the 2008 season in the
Atlantic Basin. Tropical Storm Fay made landfall in the Florida Keys in
August, and Hurricanes Hanna and Ike affected the Eastern Seaboard and
Gulf Coastal regions, respectively, during September. For each of these
TC, PRE development, if any, will be examined. Factors which enhanced,
or discouraged PRE formation will also be discussed.

**Use of the Nondivergent Wind for Diagnosing Banded Precipitation
Systems**

Thomas J. Galarneau, Jr., and Daniel Keyser

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

Mesoscale bands modulate the spatial distribution and intensity of
precipitation associated with cyclones. Cold-season examples include
snowbands within coastal extratropical cyclones, and warm-season
examples include rainbands along coastal fronts associated with
landfalling and transitioning tropical cyclones. Previous work has shown
that for cold-season coastal cyclones, mesoscale band formation occurs
in conjunction with deep-layer frontogenesis that slopes toward colder
air. The mesoscale band forms on the warm-air side of the frontogenesis
maximum in the presence of weak moist symmetric stability. In this
presentation, we will compare diagnostic signatures of vertical motion
forcing, frontogenesis, and moist symmetric stability for mesoscale
precipitation bands within the northeast U.S. cyclones of 14 February
and 16 April 2007 using the nondivergent wind (**V**~nd~), geostrophic
wind (**V**~g~), and full wind (**V**) in a balanced dynamical
framework. The diagnostics considered here are **Q** divergence,
Petterssen frontogenesis, and saturation equivalent potential vorticity
(EPV\*).

The purpose of this presentation is to extend the applicability of the
balanced framework in diagnosing mesoscale circulation systems by using
**V**~nd~ in place of **V**~g~ and **V**. The rationale for considering
**V**~nd~ is that it is expected to better represent the balanced wind
in curved flow than **V**~g~ or **V**. Use of **V**~nd~ is further
motivated by continuing increases in the horizontal and vertical
resolution of global analyses. While increases in analysis resolution
have resulted in the improved representation of mesoscale circulation
systems, these increases also have resulted in noisier diagnostic
signatures of mesoscale circulation systems using **V**~g~ and **V**.
Use of **V**~nd~ in a balanced dynamical framework is hypothesized to
produce cleaner and more coherent diagnostic signatures of mesoscale
circulation systems than **V**~g~ and **V**.

The results show that using **V**~nd~ in place of **V**~g~ and **V**
produces improved diagnostic signatures of **Q** divergence, Petterssen
frontogenesis, and EPV\* within banded precipitation systems for the
northeast U.S. cyclones of 14 February and 16 April 2007. The improved
diagnostic signatures for these two cases agree with previous work on
mesoscale band formation, indicating the band forms on the warm-air side
of a deep-layer frontogenesis maximum that slopes toward colder air in
the presence of weak moist symmetric stability. In particular, the use
of **V**~nd~ in the EPV\* calculation minimizes the spatial extent of
EPV\* \< 0 and the occurrence of localized regions of EPV\* \<\< 0. It
is suggested that this modification to the EPV\* calculation produces a
more accurate assessment of the contribution of conditional symmetric
instability to the formation and evolution of mesoscale precipitation
bands.

**A Climatology of High Lapse Rates and Associated Synoptic-Scale Flow
Patterns over North America and the Northeast US**

Jason M. Cordeira, Thomas J. Galarneau, Jr., and Lance F. Bosart

Department of Earth and Atmospheric Sciences, University at Albany,
State University of New York, Albany, New York

Atmospheric instability, in the presence of low-level moisture and
forcing for ascent, has been demonstrated as an important ingredient
when forecasting the development of deep, moist convection (DMC). This
instability can be produced by the superposition of elevated high lapse
rates (e.g. diabatically-induced mixed layers generated over an elevated
semi-arid source region and/or dynamical-driven processes associated
with upper-level troughs and jet streaks) above a region of low-level
warm, moist air. Given that instability is an important ingredient to
the development of DMC, the purpose of this presentation is two-fold:
(1) establish an annual and seasonal climatology of high lapse rates
over North America and (2) examine regional and synoptic-scale composite
flow patterns associated with occurrences of high lapse rates over North
America with an emphasis on the Northeast US.

The lapse rate climatology was generated using the North American
radiosonde network archive at the National Climatic Data Center from
1974−2007. The filtering of radiosonde observations counted the
occurrence of high lapse rates when the 700--500-hPa lapse rate was ≥
8.0 K km^−1^. The climatology was restricted to radiosonde observations
taken during the time period 1000--1400 UTC to avoid data contamination
by the presence of DMC as much as possible. Synoptic-scale flow pattern
composites were generated using the NCEP-NCAR Reanalysis at stations for
days meeting the high lapse rate threshold and were stratified by
representative mean 700--500-hPa potential temperatures.

Results highlight a warm-season maximum in high lapse rates over the
Intermountain West that expands poleward during March through August,
and extends eastward over the southern Great Plains during March through
May and east over the Northern Great Plains and Ohio Valley region
during June through August. A cold-season maximum in high lapse rates
over the Gulf of Alaska region expands equatorward along the Rocky
Mountains and extends eastward across the Canadian and US Plains from
November through March. The eastward extension of high lapse rates into
the Northeast during the warm season is likely associated with the
advection of high lapse rates poleward of the climatological summer-time
upper-level anticyclone with an origin over the Intermountain West,
while the cold-season extension is likely associated with the evolution
of high lapse rates beneath migratory cold upper-level troughs.

**Here a TC, There a TC, Everywhere a TC: The \"Spin\" on the Active
Part of the North Atlantic 2008 TC Season**

Lance F. Bosart, Thomas J. Galarneau, Jr., and Jason M. Cordeira\
Department of Earth and Atmospheric Sciences , University at Albany,
State University of New York, Albany, New York

During mid-August through mid-September 2008 six tropical cyclones
(TCs), Fay, Gustav, Hanna, Ike, Josephine, and Kyle, formed over the
North Atlantic Ocean and threatened coastal regions of the United
States. Fay, Gustav, Hanna, and Ike made coastal landfalls in the United
States, while Kyle made landfall over Atlantic Canada. Josephine never
reached hurricane status and eventually died over the North Atlantic. A
distinguishing feature of this concentrated period of North Atlantic TC
activity was the apparent multiple interactions between individual
storms and their associated outflow anticyclones. Also of interest was
the reinforcement of the potentially warm upper-level outflow
anticyclone from Ike by a similar potentially warm upper-level
anticyclone from eastern North Pacific TC Lowell.

The purpose of this presentation is twofold. First, the structure of the
large-scale environment that governed a very active part of the 2008
North Atlantic TC season will be reviewed with emphasis on the mutual
interactions between individual TCs and associated storm-track
predictability issues. Second, the precipitation characteristics of
selected storms will be discussed and reviewed with emphasis on the
predecessor rain event (PRE) over the Chicago area associated with Ike,
the \"pseudo\" PRE that formed in association with Hanna and moved
through the Albany area, and the role of surface boundaries as a focus
of heavy rainfall.

**Acknowledgements**

***Center for Environmental Science and Technology Management***

*Conference Facilities*

***Peggy Kelly***

*Hotel & Travel Coordination*

***Steve DiRienzo, Kenneth LaPenta, Warren Snyder, Jeff Tongue,***

*10 Years of NROW*

*Northeast Regional Operational Workshop Preprint Cover Images*

***Warren R. Snyder***

*Northeast Regional Operational Workshop Coordinator*

*Northeast Regional Operational Workshop Preprints*

*Northeast Regional Operational Workshop Preprint Cover Design*

***Capital Region of New York Chapter of American Meteorological
Society***

*Snacks & Refreshments*

***Vasil Koleci & Ingrid Amberger***

*Web Team*