**Agenda**

**Northeast Regional Operational Workshop VIII**

**Albany, New York**

**Wednesday, November 1, 2006**

**8:45 am**

**Welcoming Remarks**

Eugene P. Auciello, Meteorologist In Charge

Warren R. Snyder, Science & Operations Officer

National Weather Service, Albany, New York

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

Session Chair -- Thomas Wasula

**9:00 am**

**The 17 February 2006 Severe Weather and High Wind Event across Eastern
New York and New England**

Thomas A. Wasula

NOAA/National Weather Service, Albany, New York

**9:20 am**

**A Multiscale Examination of a Mesoscale Cyclogenesis Event in a Polar
Airstream**

Thomas J. Galarneau

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

**9:40 am**

**Northwest Flow - Watch Out: Experience With a Dangerous Canadian
Export**

David Zaff

NOAA/National Weather Service, Buffalo, New York

**10:00 am**

**Break**

**10:30 am**

**Orographic Forcing, Stable Stratification, and a Labrador Retriever:
The 4 March 2006 Snowfall in Northern Vermont**

Peter C. Banacos

NOAA/NWS/Weather Forecast Office, Burlington, Vermont

**10:50 am**

**A Multi-Scale Analysis of the Perfect Storms of 1991**

Jason M. Cordeira

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

**11:10 am**

**Support for High Impact Sub-Advisory Winter Precipitation Events Along
Interstate 80 in Central Pennsylvania: A Partner Project with the
Pennsylvania Department of Transportation and the Pennsylvania State
Police**

Gregory A. DeVoir

NOAA/National Weather Service, State College, Pennsylvania

**11:30 am**

**Lake Effect Thunder‑Snows Over the Eastern Great Lakes**

Robert Hamilton

NOAA/National Weather Service, Buffalo, New York

**11:50 am**

**A Method to Reliably Predict Convective Modes (Organized Bands vs.
Open- Cellular Development) in Late Season Lake-Effect Snow Events**

Michael L. Jurewicz, Sr.

NOAA/National Weather Service, Binghamton, New York

**12:10 pm**

**Improving the Understanding and Prediction of Lake-Effect Snowstorms
in the Eastern Great Lakes Region - a NWS BUF and SUNY Oswego COMET
Partners project\
**David Zaff

NOAA/National Weather Service, Buffalo, New York

**12:30 pm**

**Lunch**

**2:00 pm**

**Anticyclones Cause Weather Too: An Understanding of Worldwide Strong
Anticyclones and Anticyclogenesis**

Matthew L. Doody

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

**2:20 pm\
The Small-Scale New England Coastal Bomb of 9 December 2005:\
A Near-Miss Hurricane Zeta?**

Lance F. Bosart

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

**Session B -- Modeling**

Session Chair -- Warren R. Snyder

**2:40 pm**

**Mesoscale Investigations and Modeling in the Northern Mid-Atlantic**

Paul J. Croft

Kean University, Union, New Jersey

**3:00 pm**

**Correlations between Observed Snowfall and NAM Forecast Parameters:**

**Part 1 -- Dynamical Parameters**

Michael S. Evans

**Part 2 - Microphysical Parameters**

Michael L. Jurewicz, Sr.

NOAA/National Weather Service, Binghamton, New York

**3:40 pm**

**Exploitation of Ensemble Output at NCEP HPC**

Peter C. Manousos

NOAA/National Centers for Environmental Prediction

Camp Springs, Maryland

**4:00 pm**

Break

**4:20 pm**

**Forecast Performance of an Operational Meso-Gamma-Scale Modeling
System for Extratropical Systems**

Anthony P. Praino

International Business Machines, T.J. Watson Research Center, ACTC/Deep
Computing Systems

**4:40 pm**

**Using Wind Anomalies to Forecast East Coast Winter Storms**

Neil A. Stuart

NOAA/National Weather Service, Albany, New York

**5:00 pm**

**The Use of Ensemble and Anomaly Data during the 13-16 May 2006 New
England Record Rain Event**

Neil A. Stuart

NOAA/National Weather Service, Albany, New York

**5:20 pm**

**Simulation of Lake Effect Snow using the Workstation WRF model**

Daniel Leins

NOAA/National Weather Service, Cleveland, Ohio

**5:40 pm**

**Using a Mesoscale Model to Identify Convective Initiation in an Air
Route Traffic Control Center/Center Weather Service Unit ARTCC/CWSU)
Environment**

Warren R. Snyder

NOAA/NWS Weather Forecast Office, Albany, New York

**6:00 pm**

**ADJOURN**

**Agenda**

**Northeast Regional Operational Workshop VIII**

**Albany, New York**

**Thursday, November 2, 2006**

**Session C -- CSTAR Projects and Related Topics**

**Session Chair - Joseph P. Villani**

**9:00 am**

**The 19 April 2002 Supercell initiated by a Lake Breeze in Northwestern
Ohio**

Robert L. Tracey

NOAA Educational Partnership Program

NOAA/National Weather Service, Albany, New York

**9:20 am**

Predictability of the 22--24 January 2005 Northeast Blizzard

Heather Archambault

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

**9:40 am**

**Unexpectedly Heavy Near-Coastal Precipitation Due to Mesoscale
Features Induced by a Landfalling Tropical Storm**

Alan F. Srock

Department of Earth and Atmospheric Sciences

University at Albany, State University of New York, Albany, New York

**10:00 am**

Heavy Rainfall Events Preceding the Arrival of Tropical Cyclones

Matthew R. Cote

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

**10:20 am**

**A Climatology of Tropical Transition**

R. McTaggart-Cowan

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

**10:40 am**

**BREAK**

11:10 am

Mesoscale Precipitation Structures Accompanying Landfalling and
Transitioning Tropical Cyclones in the Northeast United States

Jared R. Klein

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

**11:30 am**

**Warm-Season Lake-/Sea-Breeze Severe Weather in the Northeast**

Patrick Wilson

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

**11:50 am**

**Lunch**

**Session D -- Warm Season Topics and Convection**

Session Chair -- John S. Quinlan

**1:30 pm**

**Derecho Formation, Evolution and MCS Interactions During BAMEX**

Nicholas D. Metz

Department of Earth and Atmospheric Sciences

University at Albany, State University of New York

**1:50 pm**

**Using Ensemble Probability Forecasts And High Resolution Models**

**To Identify Severe Weather Threats**

Josh Korotky

NOAA/National Weather Service, Pittsburgh, Pennsylvania

**2:10 am**

**The 4 August 2004 Central Pennsylvania Severe Weather Event -
Environmental and Topographic Influences on Storm Structure Evolution**

Joseph P. Villani

NOAA/NWS Weather Forecast Office, Albany, New York

**Session E -- Hydrology**

Session Chair -- John S. Quinlan

**2:30 pm**

**Northern New England Coastal Flooding**

John W. Cannon

NOAA/National Weather Service Forecast Office, Gray, Maine

**2:50 pm**

**A Flash-Flood Climatology for the National Weather Service Eastern
Region**

Alan M. Cope

NOAA/Number range CHAPTERNational Weather Service, Mount Holly, New
Jersey

**3:10 pm**

**Number range CHAPTERGIS Applications in Meteorology and Hydrology**

John S. Quinlan

NOAA/National Weather Service, Albany, NY

**3:30 pm**

**The June 2006 East Canada Creek Flood -- Forecasting a Record Category
Flood in the Absence of Real-Time Gage Data.**

Robert C. Kilpatrick

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

**3:50 pm**

**Closing Remarks**

**Warren R. Snyder**

**4:00 pm**

**ADJOURN**

**6:00 pm**

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

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

**NROW IX will be held November 7 & 8, 2007**

**The 17 February 2006 Severe Weather and High Wind Event across Eastern
New York and New England**

Thomas A. Wasula and Neil Stuart

NOAA/National Weather Service, Albany, New York

Alicia C. Wasula

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

Severe thunderstorms across New York and New England, are very unusual
and uncommon in the Winter. For example, Albany only averages about 1
thunderstorm day every decade in the month of February. A line of severe
thunderstorms producing damaging winds in excess of 50 knots (58 mph)
and large hail (greater than 1.9 cm) occurred between 1200 UTC and 1800
UTC over much of eastern New York and New England on 17 February 2006.
An anomalously strong low pressure system and its associated arctic cold
front focused an area of severe thunderstorms that developed between
1400 UTC and 1600 UTC 17 February 2006 from the northern Catskills and
Upper Hudson region in New York southwestward into northeastern
Pennsylvania. This line quickly moved through the Hudson River Valley
prior to 1600 UTC with over a dozen wind damage reports caused by the
line of severe thunderstorms over New York and New England. Widespread
wind damage subsequently followed with powerful gradient winds (numerous
gusts in excess of 50 knots) in the wake of the cold front.

Most of eastern New York and New England were in a warm sector that
morning with temperatures in the 10-15°C range prior to the cold frontal
passage. Eastern New York and New England were located in the favorable
left front quadrant of mid- and upper-level jet streaks with strong
divergence aloft. A line of convection developed in the highly sheared
environment (0-6 km values in excess of 60 knots) with little
instability. The 1200 UTC sounding from Albany revealed little or no
instability ahead of the frontal passage, which made short term
forecasting of the severe convection a few hours in advance difficult;
however, the cloud to ground lightning strikes associated with the line
of severe thunderstorms increased forecast awareness of the possibility
of severe thunderstorms. The 850 hPa low-level jet strengthened to 60-70
kts with momentum mixing down from that level, just ahead and in the
wake of the cold front. Temperatures tumbled 5-10°C with the frontal
passage coupled with pressure rises of 12-16 hPa in 3 hours. Wind gusts
of 52 knots and 85 knots were recorded at the Albany International and
Saratoga County airports.

This talk will take a multi-scale approach analyzing the event from the
synoptic-scale to the storm scale, in order to understand the
environment that caused the anomalous and under-forecasted cool season
severe weather over the Northeast. This event will also be compared to
other narrow cold frontal rainbands produced by strongly forced
low-instability lines appearing in the literature. Observational data
used in the analyses include surface and upper air observations,
satellite imagery, and KENX WSR-88D data. A variety of model guidance
including the North American Regional Reanalysis and NAM 40km data will
be shown in the presentation.

**A Multiscale Examination of a Mesoscale Cyclogenesis Event in a Polar
Airstream**

Thomas J. Galarneau, Jr., Daniel Keyser, and Lance F. Bosart, Department
of Earth and Atmospheric Sciences, University at Albany, State
University of New York, Albany, New York

Occasionally, subsynoptic-scale cyclones known as polar lows develop in
arctic air masses that trail precursor extratropical synoptic-scale
cyclones. The characteristic scale of polar lows ranges between 500 and
1000 km, which is smaller than that of their synoptic-scale
counterparts. Polar lows have been documented to occur over the northern
Pacific and Atlantic Oceans when arctic air masses move over relatively
warm water and produce regions of enhanced baroclinicity and deep moist
convection. Polar lows occasionally can generate locally heavy
precipitation and near-hurricane force surface winds. Polar lows also
can form over continental regions in midlatitudes, and in conjunction
with upper-level short-wave disturbances that may correspond to coherent
tropopause disturbances (CTDs) of arctic origin. The relatively low
height and low potential temperature of the dynamic tropopause (DT) in
arctic CTDs serves to increase the likelihood that the CTD can couple
with a surface disturbance in the presence of a baroclinic zone. The
purpose of this presentation is to examine two polar lows that generated
localized regions of heavy snow and cloud-to-ground lightning over the
northeast United States on 5 April 2006.

The examination shows that the polar lows developed on the cyclonic
shear side of an upper-level jet within a region of cyclonic vorticity
advection associated with a CTD. The polar lows exhibited a comma cloud
structure and formed within a baroclinic environment, which is
consistent with the characteristics of the short-wave/jet-streak type of
polar low discussed in Businger and Reed (1989). Given that these polar
lows formed over land, it is suggested that a low, cold DT and steep
lapse rates associated with a CTD of arctic origin may be able to mimic
the effect of oceanic latent and sensible heating, which destabilizes
the lower troposphere and creates an atmospheric stratification
favorable for vigorous ascent and cyclogenesis.

**Northwest Flow - Watch Out:**

**Experience With a Dangerous Canadian Export**

David Zaff

NOAA/National Weather Service, Buffalo, New York

Typically, meteorologists across the Great Lakes region tend to look to
the southwest during the summer for indications of severe weather, often
associated with warm frontal boundaries and high dewpoints.  However,
numerous studies have shown that some of the worst convective storms are
associated with west or northwest flow aloft, particularly after the
spring convection season transitions to summer. 

Over Western New York, a convective outbreak under northwest flow
typically occurs as a shortwave moves across the region associated with
a cool upper level trough located over southern Ontario.  Upper level
dynamic support and lift then combine with low level convergence along
lake breeze boundaries formed during diurnal heating.  Sometimes the
shortwave will produce convection in southern Ontario early on, which
rapidly intensifies as it encounters these boundaries.  The three
features, a shortwave, northwest flow under an upstream upper level
trough, and lake breezes, are a combination that requires forecasters to
heighten their awareness for the potential of severe weather across
Western New York. 

Three 2006 summer severe weather events across the Metro Buffalo area
occurred under these conditions.  The first of the three events was
markedly similar to an event that occurred on July 30, 1987, where an F2
tornado touched down in Cheektowaga, NY.  This time, on June 30, 2006,
an F1 touched down, only about a mile from the 1987 event and with a
similar track.  The second event occurred on July 23, 2006.  This time a
funnel cloud was witnessed in Cambria along several reports of large
hail.  During a third recent event, July 28, 2006, a few severe
thunderstorm warnings were issued.  This event was minor, with only some
trees reported down in Sanborn, NY.  This talk will primarily focus on
the meteorological details leading up to the first case, as tornadoes in
the Buffalo area clearly generate significant media attention. 
Comparisons between this event and the 1987 event will be discussed. 
Finally, comparisons between the tornadic events of 1987 and 2006 and
the other recent non-tornadic events will be made. In all cases however,
the message is clear: under northwest flow, watch out!

**Orographic Forcing, Stable Stratification, and a Labrador Retriever:
The 4 March 2006 Snowfall in Northern Vermont**

Peter C. Banacos

NOAA/NWS/Weather Forecast Office

Burlington, Vermont

Orographic forcing exerts a first-order influence upon the distribution
of precipitation in areas of complex terrain. In winter, the west slopes
of Vermont's Green Mountains typically receive higher snow accumulations
when sufficient moisture exists in strong, low-level northwesterly flow.
These episodes of upslope precipitation enhancement are often
characterized by low-level cold advection, steep near-surface lapse
rates, and a synoptic regime which includes a deep cyclone northeast of
the region.

During the overnight hours on 4 March 2006, large snow accumulations
occurred with northwest low-level flow not only in areas commonly
affected by orographic enhancement, but also across the Vermont portion
of the Champlain Valley, 15-25 km west of the mountains. The Burlington
International airport set a daily snowfall record, with a storm total
snowfall of 14.2 in (36.1 cm), and snow accumulation rates of 1-2 in/hr
(2.5-5 cm/hr) for eight consecutive hours. The median snow-to-liquid
equivalent ratio in the area was approximately 40:1.

This presentation offers an observational perspective on the favorable
combination of large-scale, mesoscale, and microphysical factors that
led to the snowfall. First, a strong high-latitude block existed near
Greenland preceding the event. Second, a quasi-stationary polar vortex
over eastern Quebec and Newfoundland served as a pivot point for the
"retrieval" of shortwave troughs from off the Labrador coast westward
and then southward into northern New England. A particularly vigorous
trough, with an associated mid-level jet (up to 105 kt at 500 mb) and
strong *equatorward* 925-700 mb layer warm advection, moved into
northern Vermont after 00 UTC on 4 March. Third, the unusual, strong
low-level warm advection from the north led to a temperature inversion
below the Green Mountain ridge line. It is hypothesized that this stable
stratification allowed the orographic forcing to be induced further
upstream from the mountain barrier than normal, which is consistent with
limited observational work from the western U.S. concerning the
modulating role of static stability on upslope precipitation. Fourth, a
saturated surface-700 mb layer (\~ 2.5 km deep), with temperatures
favorable for dendrite growth, maximized precipitation efficiency during
the period of warm advection and orographic forcing.

This case illustrates the importance of various mechanisms in the
development of heavy snowfall, and demonstrates that a stable thermal
stratification does not necessarily preclude large snow accumulations.

**A Multi-Scale Analysis of the Perfect Storms of 1991**

Jason M. Cordeira and Lance F. Bosart, Department of Earth and
Atmospheric Sciences, University at Albany, State University of New
York, Albany, NY

The extreme weather events in the US that occurred in late October and
early November of 1991, known as the "Perfect Storms", transpired during
highly amplified and anomalous large-scale flow regime transitions. This
transition is exemplified through the Pacific North American index as a
total positive-negative-positive transition of 8.8 standard deviations
over 25 days. During the transitions the flow remained amplified and
assisted in the development of two meteorologically significant and
"perfect" storms. The purpose of this presentation is to document the
life cycles of these twin extreme weather events via a multi-scale
diagnostic analysis.

The first of the Perfect Storms began with an extratropical, baroclinic
cyclone east of Nova Scotia on 28 October embedded downstream of a
highly amplified mid-level trough-ridge flow pattern over the US. The
cyclone's deep circulation quickly became the foremost feature in the
northwest Atlantic as it overtook Hurricane Grace to its south. The
extratropical cyclone continued to strengthen to 972 hPa as it
propagated westward towards the US and then subsequently weakened as it
performed a counter-clockwise loop in the far western Atlantic beneath
the building ridge. The warm waters of the Gulf Stream then excited
convection within the center of the Perfect Storm, yielding the
development of the "Unnamed Hurricane" on 2 November.

The second of the Perfect Storms began as a positive (cyclonic)
upper-level potential vorticity (PV) anomaly rotating through the trough
in the western US. As this PV anomaly approached the western Gulf of
Mexico it induced development of a weak surface cyclone over the extreme
western Gulf of Mexico. This cyclone strengthened and propagated
poleward as the mid-level trough tilted negative on 1 November. A strong
(1050 hPa) surface anticyclone propagating southward from Canada
provided anomalously cold air (\~ -3σ) that aided in giving Minnesota
its earliest and heaviest snowfall totals, setting the state record for
storm-total snowfall of 93.7 cm in Duluth, MN. By the end of the life
cycles of these two storms, the large-scale flow regime had once again
reversed.

The presented research will focus on (1) the extratropical transition of
Hurricane Grace and the development of the first Perfect Storm and its
subsequent tropical transition, (2) the development and life cycle of
the second Perfect Storm, and (3) linkages between the two Perfect
Storms including, trajectory and time series analyses, potential
vorticity, and teleconnections associated with the large scale flow
regime.

**Support for High Impact Sub-Advisory Winter Precipitation Events Along
Interstate 80 in Central Pennsylvania: A Partner Project with the
Pennsylvania Department of Transportation and the Pennsylvania State
Police**

Gregory A. DeVoir and Richard H. Grumm

NOAA/National Weather Service, State College, Pennsylvania

In recent years the meteorological, emergency management (EMA) and law
enforcement communities have gained an increased awareness of the
threats associated with High Impact Sub-Advisory (HISA) winter
precipitation events. HISA refers to weather phenomena including
precipitation amounts (i.e., snow accumulations) which fall short of
meeting National Weather Service (NWS) Advisory (headline) criteria, yet
still pose a substantial hazard to the public.

HISA snow events have been responsible for a series of disastrous chain
reaction accidents in Pennsylvania over the last several years. The most
severe of these occurred 6 January 2004 near Bellefonte, PA, and
resulted in a fiery 44-vehicle pile-up which killed 6 people and injured
two dozen others. Despite forecasts calling for intense snow squalls
issued hours in advance, motorists were caught off guard by sudden
whiteout conditions and icy roads as temperatures plummeted behind an
arctic cold front.

The NWS office in State College, Pennsylvania has built partnerships
with the Pennsylvania Department of Transportation (PENNDOT) and the
Pennsylvania State Police (PSP) over the past several years. The result
of this effort has been the implementation of an event notification
system by which affected PENNDOT districts and the PSP can be alerted
for potential HISA events, sometimes days in advance. Once notified,
preventative actions can be taken, including leveraging of resources and
pre-treatment of roads where needed. While it is recognized that
accidents associated with HISA events can never be completely avoided,
it is hoped that their impact and severity in terms of loss of life and
property can be mitigated through the early notification system.

The characteristics and impacts of several central Pennsylvania HISA
events will be discussed. Specific details of the NWS State College PA
partnership project with PENNDOT and the PSP will be presented, along
with an overview of the event notification system. Ongoing and future
work will focus on identifying critical event "fingerprints" from
retrospective high-resolution model simulations, which may be used to
anticipate HISA events with greater lead time.

**Lake Effect Thunder‑Snows Over the Eastern Great Lakes**

Robert Hamilton

NOAA/National Weather Service, Buffalo, New York

Scott Steiger, Ph.D.

State University of New York, Oswego New York

Heavy lake effect snows typify winter weather across Western New York as
intrusions of arctic air generate snowfall amounts that are often
measured in feet.  While significant snowfall is produced from these
events with convective outbursts capable of producing rates of 2 to 4
inches an hour, they are usually very localized in aerial coverage.

These impressive mesoscale events are occasionally highlighted by
lightning and thunder. Lightning-bearing lake effect snows across
Western New York typically occur early in the winter season. The surface
temperatures of Lakes Erie and Ontario are still relatively \"warm\" at
that time of year. In addition, the depth of the surface to -10C layer
is still several thousand feet thick.

Higher lake temperatures and a deeper boundary layer appear to be
critical components that allow for abundant graupel production. The
increased graupel is a crucial element in helping to produce an
electrical charge, both by its electrostatic properties and through its
role in building a static charge through frictional collisions with
smaller ice particles and super cooled water droplets. Current
electrification models strongly support the theory that graupel
production in the ‑10C to ‑20C layer is essential for the beginning
stages of lightning production. The depth of the surface to -10C layer
is also extremely important in terms of allowing for charge separation.

This research has been conducted using nearly 10 years worth of sounding
and ETA model data, dating from the winters of 1996‑97 through
2005‑2006.  Results of this study on Western New York thunder-snow
events suggest that if the depth of the surface to -10C is too shallow
then graupel cannot be produced and lightning is much less likely. 
Various other convective parameters such as vertical velocity, CAPE, and
equilibrium level are also examined to determine their possible
contribution to lightning production in lake effect snow.

This presentation will show the importance of the lake water temperature
in generating graupel which is crucial to developing an electrical
charge within the lake effect clouds.

**A Method to Reliably Predict Convective Modes (Organized Bands vs.
Open- Cellular Development) in Late Season Lake-Effect Snow Events**

By Michael L. Jurewicz, Sr.

NOAA/National Weather Service, Binghamton, New York

Lake-effect snow has long been a challenging phenomenon for operational
meteorologists. This is particularly true late in the winter season,
when the increased sun angle adds further complexity to the situation by
altering the organization of lake-effect snow bands. Local experience
indicates that late season lake-effect snow undergoes changes in
structure that are closely tied to the diurnal heating cycle; cellular
structures are most often observed during the afternoon and evening,
while organized bands (with the heaviest accumulations) are more often
observed during the late night and morning hours. However, there are
instances when the structural evolutions of lake-effect snow do not
follow this simple diurnal pattern; indicating there are other factors
in play. The goal of this study is to identify these other factors that
affect the organization of lake-effect snow bands late in the winter
season.

Due to their convective nature and typically shallow depth, the overall
structure of lake-effect snow bands tends to be governed by the same
atmospheric principles that influence horizontal convective rolls. Prior
research on these rolls, using both idealized numerical simulations and
observations, indicates that their definition and intensity are
modulated mainly by lower-tropospheric wind shear and boundary layer
heat fluxes. Observational studies indicated that strong
lower-tropospheric speed shear environments were associated with well
defined lake-effect snow bands over Lakes Erie and Michigan, as well as
the Great Salt Lake. Conversely, when the vertical speed shear
decreased, there was a tendency for disorganized open-cellular
convection to prevail. It has also been shown that increased
lower-tropospheric instability (greater differential between lake
surface and air temperatures), especially in the absence of pronounced
vertical shear, has a similarly detrimental effect on roll organization
and longevity.

For this project, archived radar images, observations, and initial-hour
North American Mesoscale (NAM) model soundings were examined for the
months of February, March, and April, over a four year period
(2003-2006) in Central New York State. It was found that shear and
instability parameters (bulk speed shear in the mixed layer and CAPE),
quantified within the BUFKIT sounding program, can be used to accurately
forecast convective modes in lake-effect snow situations. Based on these
results, forecasters will be able to use BUFKIT soundings to be more
specific with the timing of any expected changes in convective mode.
Since organized banding typically produces much heavier snow
accumulations than cellular convection, this will produce a significant
upgrade in our ability to forecast snowfall amounts. It will also be
shown that this proposed method has skill over merely considering
diurnal trends in stability and their usual effect on the cohesiveness
of lake-effect snow bands.

 

**Improving the Understanding and Prediction of Lake-Effect Snowstorms
in the Eastern Great Lakes Region - a NWS BUF and SUNY Oswego COMET
Partners project\
**

David Zaff

NOAA/National Weather Service, Buffalo, New York

Lake-effect snowstorms are intense, banded mesoscale phenomena that
occur in late fall and winter downwind of the Great Lakes (Reinking et
al. 1993 and Kristovich et al. 2000).  These storms produce enormous
impacts across the region.  Over the eastern Great Lakes they disrupt
commerce and transportation in the cities of Buffalo, Rochester, and
Syracuse, as well as on major interstates, such as I-90 and I-81.  These
bands are often quite narrow, usually 10-20 km wide. 

A wealth of research has focused on these events over the past two
decades, but forecasters are still challenged with forecasting them.  In
particular, it is still difficult to attain accurate predictions of a
lake band\'s timing, intensity, location, and inland extent as well as
snowfall rates and snow to water ratios.  The National Weather Service
Forecast office in Buffalo (NWS BUF) and the Meteorology program at the
State University of New York at Oswego (SUNY Oswego) have begun a
year-long Cooperative Program for Operational Meteorology, Education,
and Training program (COMET) designed to attempt to help meteorologists
and students improve our understanding of the environmental and
geographical conditions that affect these snow bands by using the
Weather and Research (WRF) Model (Skamarock et al 2005). 

Specifically, this project aims to 1) determine an optimal model
configuration (horizontal and vertical resolution, and domain size) that
improves lake effect forecasts for a variety of lake effect scenarios 2)
attempt to improve forecasting the inland extent of significant
accumulations 3) increase an understanding of the diurnal variability of
snow band intensity and structure 4) further the understanding of the
effects of topography and 5) investigate the sensitivity of lake-induced
circulations to environmental factors by using the WRF model in
idealized experiments.  This project is in its early stages; several
case studies have been selected and are being tested and rerun with the
WRF model.  Each case study covers a different type of lake effect
event, eg, those that develop off of southwest flow vs those that
develop off of northwest flow. This talk covers some of these cases,
comparing the operational forecast models with NWS forecasts and storm
observations.  Some preliminary results of the WRF run on one case will
also be discussed.

**Anticyclones Cause Weather Too: An Understanding of Worldwide Strong
Anticyclones and Anticyclogenesis**

Matthew L. Doody, Lance Bosart, and Daniel Keyser

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

Intense anticyclogenesis historically has been less studied than intense
cyclogenesis, a situation that likely reflects the perception that
intense anticyclones are associated with less widespread hazardous
weather. However, intense cool-season anticyclones are often associated
with the strongest continental cold surges and associated widespread
severe cold, snow, and ice problems in midlatitudes. The purpose of this
presentation is to present a global climatology of intense cool-season
anticyclones and to establish the basis for an investigation of the
dynamics and predictability of strong anticyclogenesis. To assist in
this endeavor, anticyclone frequencies will be mapped on annual,
seasonal, and monthly time scales. Continental versus oceanic and
Northern Hemisphere (NH) versus Southern Hemisphere (SH) anticyclone
frequencies will also be mapped.

The global gridded 2.5 degree NCEP/NCAR and ERA-40 datasets were used to
perform this study. Gridded fields of sea level pressure (SLP) and 1000
hPa geopotential heights were extracted from these datasets. At each
grid point a counter kept track of the number of times an SLP threshold
(e.g., 1050 hPa) was exceeded. Global, NH, and SH anticyclone frequency
distributions were then constructed for the specified thresholds.
Annual, seasonal, and monthly anticyclone frequency distributions were
mapped for the assigned selection thresholds.

A comparison of the two global gridded datasets was performed to assess
analysis uncertainty. Significant differences were noted over areas of
elevated terrain (e.g., Greenland) where the NCEP/NCAR analyses showed a
higher frequency of intense anticyclones than in the ERA-40 analyses.
This difference was noted to be true globally throughout most of the
regions with higher terrain. Intense cool-season NH anticyclones
populated mostly higher-latitude, snow-covered, continental regions,
whereas intense cool-season SH anticyclones (1040+ hPa) dominated the
midlatitude oceanic storm tracks. In the NH, intense cool-season
anticyclone frequency maxima extended equatorward along the eastern
margins of major topographic barriers (e.g., the Rockies). A minimum in
intense anticyclone frequency was found over and to the west of major
topographic barriers. Time permitting an illustrative example of intense
cool-season anticyclogenesis that impacted the northeastern United
States will be presented.

**The Small-Scale New England Coastal Bomb of 9 December 2005:\
A Near-Miss Hurricane Zeta?**

Lance F. Bosart

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

Between 0600-1200 UTC 9 December 2005 a small-scale secondary cyclone
developed just to the east of the Delmarva Peninsula. This cyclone moved
northeastward along the coast and intensified rapidly (hourly pressure
falls reached 10 hPa over parts of Cape Cod and the Islands) as it
approached and crossed extreme southeastern New England.

Between 1700-2000 UTC, as the cyclone crossed Cape Cod, KBOX base
reflectivity observations showed that a tight inner vortex had formed.
Intense snowfall rates (10-15 cm h^-1^) occurred along the bent-back
frontal system in the western semi-circle of this vortex. Deep
convection was observed near the center of the vortex and along parts of
the bent-back frontal system where heavy snow was reported. Peak
westerly wind gusts in excess of hurricane force (75 kt) were observed
with the wind shift immediately behind the cyclone and near the
southwest tip of the bent-back frontal system. The wind/pressure
signatures seen near the center of the cyclone and the observed
\"eye-like\" feature observed in the KBOX base reflectivity observations
suggested that the cyclone possessed several \"hurricane-like\"
characteristics. The purpose of this presentation will be to 1) document
the large-scale environmental impact on cyclone formation, 2) to
illustrate the cyclone's mesoscale structure and evolution, and 3) to
comment on aspects of the cyclone's development that have some
similarity to tropical cyclogenesis.

**Mesoscale Investigations and Modeling in the Northern Mid-Atlantic**

Paul J. Croft and Shing Yoh

Kean University, Union, New Jersey

The occurrence of mesoscale weather variations is of interest across New
Jersey and in the immediate vicinity of the Northern Mid-Atlantic given
its high population density as well as a wide diversity of land use,
physiographic features, and the wide range of impacts from both
hazardous weather and even "routine" conditions (e.g., local wind
circulations). In an attempt to ascertain the characteristics and
behaviors of these, efforts are underway at Kean University to involve
students in local studies through targeted investigations and modeling
of specific features and phenomena. During the past two years, students
have performed investigations of characteristics and behaviors of cool
season severe weather; winter season fog; spatial patterns of the air
quality index in various weather regimes; October tropical cyclones; the
rain-snow line; the sea breeze; and most recently summer season
convective initiation and lightning patterns. Some initial results and
findings on this work are presented to illustrate these efforts.

The intent has been to examine, from an operational perspective, the
types of data and analyses that would best assist a forecaster in the
spatial and temporal specification of the resultant sensible weather
conditions and to determine how these vary with time as a function of
local effects (e.g., physiography), mesoscale features, and the
prevailing synoptic scale flow. Students have accessed large and diverse
data in real-time, as well as from archived sets as available, to
portray conditions and their variations with time and from case to case.
Specific locations within the state of New Jersey were also selected so
as to consider direct versus regional impacts. Composite analyses and
numerical modeling (e.g., WRF), as well as the use of GIS programs and
applications, have been prepared in an effort to assess the relative
importance of select parameters and identify characteristics and
behaviors pertinent to each investigation (e.g., initiation,
distribution, evolution, movement, and coverage of convection). Initial
results have provided information relevant to the identification of the
family of local factors and their modes of behavior that will be useful
in operational applications.

The investigations form the basis of the SECURED program (Student
Educational Collective for Undergraduate Research Experiences and
Development) at Kean University. They compose the Kean University
Operational Undergraduate Research in Meteorology & Professional
Activities and Collaborative Training program (KU-OUR-METPACT) which
continues in GROWTH (Growth through Research in Operational Weather --
Training Holistically). In order to accomplish these, the Department of
Geology and Meteorology has established a variety of partnerships in the
region (e.g., NWS, ONJSC, Private Sector) to tailor research to
operational needs and outcomes. Both external and internal (e.g., the
SpF Program at Kean University) support have been sought to fund both
student stipends as well as needed supplies and/or equipment relative to
the research activities.

**Correlations between Observed Snowfall and NAM Forecast Parameters:
Part 1 -- Dynamical Parameters, Part 2 - Microphysical Parameters**

Michael S. Evans and Michael L. Jurewicz, Sr.

NOAA/National Weather Service, Binghamton, New York

Mesoscale and microscale factors that lead to enhanced snowfall in
winter storms have been a topic of extensive research during the past
several years. Research has shown that bands of heavy snow are often
explained dynamically in terms of a thermally direct circulation
associated with strong, steeply sloped lower to mid-tropospheric
frontogenesis, which becomes co-located with a region of reduced or
negative stability to slantwise motions. In cases of lighter but still
significant bands of snow, recent research has shown that the thermally
direct circulations are weaker, shallower, and less persistent than in
heavier events. Based on this research, forecasters engaged in
predicting snowfall have been trained to look for favorable
configurations of frontogenesis and reduced or negative stability \[as
indicated by small or negative values of saturation equivalent potential
vorticity (EPV)\]. However, little guidance is currently available on
how to translate the existence, intensity, and persistence of these
signatures into actual snowfall amounts. Regarding the microscale,
research has shown that enhanced snowfall can occur when significant
lift occurs in layers with temperature structures that are favorable for
dendritic snow crystal growth (dendrite-production layers). Again,
except for some algorithms related to snow-to-liquid ratios, little
guidance is available to forecasters on how specifically to modify
snowfall forecasts based on the existence of co-located upward vertical
motion and a favorable thermal profile.

The goal of this study is two-fold. First, to validate the utility of
examining frontogenesis, EPV, vertical velocity, and temperature
profiles for snowfall forecasting. Second, to provide forecasters with
guidance on forecasting snowfall amounts, based on thresholds of
intensity and persistence of these parameters. To accomplish these
goals, data from 29 snow events in central New York and northeast
Pennsylvania were examined. Event-maximum snowfall in these cases ranged
from 4 to 34 inches. For each event a representative time and location
within the area of heavy snow was identified. Data valid at these times
and locations were analyzed in both cross-sectional and time-height
formats. Values of relevant parameters were recorded for each event.
Part one of this study focuses on correlations between snowfall and
dynamical parameters such as frontogenesis, EPV, and omega. Part two of
the study focuses on correlations between snowfall and factors related
to precipitation efficiency, such as co-location between upward motion
and a favorable thermodynamic profile

Preliminary results will be presented that indicate that every storm in
the database was associated with a 12-hour forecast of at least one
layer of frontogenesis below 500 hPa, and at least one layer of negative
EPV below 400 hPa. Therefore, it appears that merely identifying the
existence of those two factors is not enough to allow forecasters to
conclude anything about storm-total snowfall amounts. However, strong
correlations were found between observed snowfall and factors that were
related to depth and persistence of co-located upward vertical motion
and negative EPV. The fact that these correlations were stronger than
the correlations between observed snowfall and persistence and depth of
upward vertical motion (EPV not considered) implies that there is
significant value in looking for negative EPV in the forecast process.
Strong correlations were also found between observed snowfall and
maximum upward vertical motion within dendrite-production layers, while
somewhat weaker correlations were found between snowfall and vertical
motion alone (dendrite-production layer depth not considered). Evidence
will be presented that indicates that consideration of the
dendrite-production layer in the forecast process reduces false alarm
rates for light to moderate snow events. Much lower correlations were
found with 24-hour forecasts of many of these parameters, due primarily
to a few major model forecast busts.

Details of the above correlation methodology, resulting correlations,
forecasting thresholds, and threshold statistics will be presented.

**Exploitation of Ensemble Output at NCEP HPC**

Peter C. Manousos

NOAA/National Centers for Environmental Prediction

Camp Springs, Maryland

The use of ensemble output to support HPC operational products will be
discussed including application to QPF, winter weather, medium range,
and tropical cyclone forecasts. Experimental use of ensemble output will
also be presented. Additionally downscaling strategies to produce high
resolution grids and also a short term roadmap of intended model
upgrades by EMC will be provided.

**Forecast Performance of an Operational Meso-Gamma-Scale Modeling
System for Extratropical Systems**

Anthony P. Praino

International Business Machines, T.J. Watson Research Center, ACTC/Deep
Computing Systems

In our continuing work on the implementation and applications of an
operational mesoscale modelling system dubbed \"*Deep Thunder*\", we
examine its forecast performance for several events of tropical origin
over the Northeast United States. The study focused on the performance
of operational nested 24-hour model forecasts, which are typically
updated twice daily, for the New York City metropolitan area to 1 km
resolution. Explicit, bulk cloud microphysics are included in the model
predictions. All of the processing, modelling and visualization are
completed in one to two hours on relatively modest hardware to enable
sufficiently timely dissemination of forecast products for potential
weather-sensitive applications.

In order to evaluate the quality of the forecasts produced by the Deep
Thunder system at a storm-scale and its potential skill, we have
identified a number of interesting cases in which systems of tropical
origin impacted the tristate region. While the systems had become
extratropical before reaching the geography studied, they did retain
some of the structure and dynamics of their tropical genesis. We compare
the model results with observational data as well as the operational
availability of specific forecast products. Such performance is examined
by considering forecast timing, locality, intensity and structure of
convective elements of the overall system.

**The Use of Ensemble and Anomaly Data during the 13-16 May 2006 New
England Record Rain Event**

Neil A. Stuart

NOAA/National Weather Service, Albany, New York

Richard Grumm

NOAA/ National Weather Service, State College, Pennsylvania

A prolonged heavy rain event occurred in eastern New England 14-16 May
2006, resulting in record rainfall amounts and near-record flooding. The
heaviest rains were observed in eastern Massachusetts, New Hampshire and
southern Maine, where 8 to 14 inches of rain fell.

While the potential for heavy rain and flooding was well anticipated by
meteorologists across the region, the magnitude and impact was greatly
underestimated. Flood watches were issued with at least 12 hours lead
time, but forecasted rainfall amounts were roughly half what was
observed.

It will be shown that analysis of ensemble guidance in a variety of
formats provided clues 24 to 48 hours before flooding was observed that
there was an increased likelihood of more significant rainfall and
flooding than deterministic forecast models were showing. For example,
prolonged anomalous ensemble mean southeast winds at 850 hPa in the
range of -3 to -4 Standard Deviations (SD) from normal, and precipitable
water values of -2 SD from normal suggested an extended period of above
normal moisture transport and low level forcing, enhancing upward motion
and rainfall production. Plume displays of quantitative precipitation
forecasts for 15 individual ensemble members for locations around New
England also suggested a long duration heavy rainfall event.

This case demonstrates that effective use of ensemble guidance and plume
displays can aid forecasters in increasing lead times and forecaster
confidence for forecasting high impact precipitation events. Forecasters
can then add value to forecast and warning products by including the
level of confidence, in an effort to give users more specific
information and more lead time to make critical decisions.

**Simulation of Lake Effect Snow using the Workstation WRF model**

Daniel Leins and Robert LaPlante

NOAA/National Weather Service, Cleveland, Ohio

Lake Effect snow (LES) events produce significant amounts of snow from
mesoscale snow bands downwind of the Great Lakes during the winter
months. The mesoscale nature of the LES bands produce sharp, intense
gradients in snowfall that are a challenge to simulate with operational
model horizontal grid spacing in excess of 10 km. The workstation
version of the Weather Research and Forecasting (WRF) Environmental
Modeling System (EMS) with a finer resolution of 6 km was employed by
WFO Cleveland to simulate LES over northeast Ohio and northwest
Pennsylvania this past winter season. Several LES events were identified
and numerical model initial and boundary conditions were saved. WRF
sensitivity studies were conducted by varying the model horizontal
resolution from 3 to 6 km, by varying the cloud microphysical scheme,
and by varying the choice of convective parameterization scheme. Model
output will be verified with snow spotter observations to determine the
optimal model configuration, which will be used in future simulations.

**Using a Mesoscale Model to Identify Convective Initiation in an Air
Route Traffic Control Center/Center Weather Service Unit (ARTCC/CWSU)
Environment**

Warren R. Snyder

NOAA/NWS Weather Forecast Office, Albany, New York

Mark R. McKinley

NOAA/NWS Center Weather Service Unit, Oberlin, Ohio

Allison R. Vegh

Department of Earth and Atmospheric Sciences

University at Brockport, State University of New York

Brockport, New York

Thunderstorms account for 24% of all air traffic delays by significantly
diminishing the National Airspace System's (NAS) capacity to route
aircraft. The NAS is managed at Air Route Traffic Control Centers
(ARTCC) by Federal Aviation Administration (FAA) personnel, who receive
their weather forecasts and data from co-located Center Weather Service
Units (CWSU), operated by the National Weather Service. This study
provided real-time mesoscale model output from the Work Station Eta
(WSEta) to one of these CWSUs located at Oberlin, Ohio. The model data
was assessed to determine whether thunderstorm/convective initiation are
forecastable from model fields during the first 24 hours. In addition
anecdotal evidence was sought to determine the data's usefulness to the
CWSU forecasters. This study, using a 29 case dataset from August 2004
to June 2005 over the Oberlin CWSU area of responsibility, identified
three WSEta meteorological parameters that were credible predictors of
thunderstorm initiation: hourly convective precipitation, 700 hPa omega,
and 250 hPa divergence. The results from this study and the utility of
the WSEta will be presented. In addition work in progress using much
more accurate National Lightning Detection Network Data will be
presented. These cases look at the summer of 2005 across the Oberlin
CWSU and compare the model forecast of convective initiation using these
parameters, and the NLDN strokes. This data looks quite promising with
most of the events within one to two hours and

under 100 km.

**The 19 April 2002 Supercell initiated by a Lake Breeze in Northwestern
Ohio**

Robert L. Tracey and Thomas A. Wasula

NOAA Educational Partnership Program

NOAA/National Weather Service, Albany, New York

The effects of lake breezes are very important, with many urban
populaces located near the Great Lakes. Previous tornado climatologies
in the Great Lakes region have implicated lake breezes as a major factor
in tornadogenesis. On 19 April 2002 a lake breeze boundary, interacting
with a southward moving cold front, spawned a supercell in northwest
Ohio. This storm resulted in numerous hail reports, one of which was
about 5 cm in diameter, and an F0 tornado.

The synoptic environment favored upward motion in the lower to mid
troposphere. Divergence from the left exit region of a strong 65 ms^-1^
jet streak at 200 hPa, and cyclonic vorticity advection at 500 hPa
coincided favoring the vertical development of the storm. An anomalously
strong synoptic scale ridge was in place over the eastern continental
United States, with 850 hPa temperatures nearly 15°C over Ohio. The
impacts of this feature resulted in record-breaking temperatures of
25-30°C across the Midwest for 3 days prior to the event. An abundance
of low-level moisture was also prevalent, with precipitable water values
around 2.5 cm, nearly 200% of normal at that time of year.

The mesoscale environment was also very conducive for convective
development. A cross section of equivalent potential temperature showed
a very deep column of potential instability, with 330K theta-e at the
surface, and 320K theta-e at 500 hPa, over Ohio. Surface-based CAPE
values from morning soundings were also in excess of 1500 J kg^-1^.
However, deep layer shear was only marginal for supercellular
development. For example, 0-6 km shear was only 15 ms^-1^ based on the
Pittsburgh sounding that morning. Lake-land temperature differentials
supported the development of lake breezes during the late morning and
afternoon hours.

This presentation will show that the lake breezes served two purposes in
creating the supercell. First, the lake breeze boundary served as a
forcing mechanism for ascent. Second, northerly low-level winds behind
the lake breeze boundary increased the low level shear and helicity to
the necessary critical values for a mesocyclone and subsequent tornadic
development. Gridded data from the NAM and experimental 1km WRF, NCDC
Level-II radar data, SPC data, and NCEP-NARR data will all be used in
the talk.

**Predictability of the 22--24 January 2005 Northeast Blizzard**

Heather Archambault,

Josephe Kravitz, Daniel Keysey, Lance F. Bosart

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

Improving the prediction of high-impact weather such as heavy snow and
strong winds associated with extratropical cyclones poses a critical
scientific challenge. The 22--24 January 2005 blizzard that affected the
Northeast U.S. is a recent example of a high-impact weather event that
was not well forecast more than a few days in advance. Motivated by the
need to identify precursors to such events, we present a multiscale case
study of the January 2005 Northeast blizzard.

Data sources include the NCEP Global Forecast System (GFS) gridded model
forecasts and analyses, the NCEP--NCAR gridded reanalysis, and
NCEP-provided extratropical Northern Hemisphere (NH) geopotential height
anomaly correlations between GFS forecasts and analyses.

An analysis of coarse-resolution (2.5°) gridded GFS model forecasts
reveals that the strength of a short-wave trough over the Northeast at
the time of the blizzard was significantly underforecast by the GFS
model as few as two to three days prior to the event. In addition,
inspection of the fine-resolution (0.5°) gridded GFS model forecasts
indicates that the merger of three coherent tropopause disturbances
(CTDs) over the eastern U.S. just prior to the event was inadequately
resolved, likely contributing to the observed error in the position and
strength of the surface cyclone associated with the Northeast blizzard.

Results suggest that the extratropical cyclone associated with the
blizzard is partly attributable to dramatic changes in the NH
planetary-scale flow pattern in the following ways: First, the abrupt
transition from an extreme negative to an extreme positive
Pacific--North American (PNA) pattern (12--17 January) resulted in a
dynamically favorable flow regime for cyclogenesis near the eastern U.S.
coast by establishing a deep trough over the eastern U.S. and western
North Atlantic. The regime transition also facilitated an arctic cold
surge over the eastern U.S. that preconditioned the Northeast for
warm-air advection and heavy snow. Second, the eastward propagation of a
long-lived Rossby wave train initiated over the western Pacific by an
arctic CTD (18 January) may have helped spawn cyclogenesis near the
Northeast coast by amplifying the planetary-scale flow pattern. Third,
the rapid transition from an extreme positive to extreme negative North
Atlantic Oscillation pattern (18--25 January) associated with the onset
of North Atlantic blocking contributed to the development of a
meridional storm track near the eastern U.S. coast. Finally,
high-latitude northwesterly flow induced by the extreme positive PNA
pattern helped extract a deep CTD from the arctic (21 January) that
subsequently contributed to coastal cyclogenesis.

**Unexpectedly Heavy Near-Coastal Precipitation Due to Mesoscale
Features Induced by a Landfalling Tropical Storm**

Alan F. Srock, Lance F. Bosart, and John Molinari

Department of Earth and Atmospheric Sciences

University at Albany, State University of New York

Albany, New York

Landfalling and near-land tropical cyclones (TCs) provide a challenging
forecast problem, especially regarding major threats like storm surge,
high winds, and heavy rainfall. Generally, the dangers from strong winds
and storm surge weaken rapidly with increasing distance from the core of
the circulation. However, the precipitation structure associated with a
landfalling TC is far more variable, and is much more likely to have
maxima far removed from the main circulation. These distant maxima are
often found in regions where the flow around the TC is interacting with
land and terrain features. Thus, mesoscale phenomena such as coastal
fronts, orographic enhancement, and cold air damming can have a marked
influence on the areal precipitation coverage, even while the storm is
greater than 300 km away. Generally considered as cold-season phenomena
associated with a high pressure system to the north, coastal fronts and
cold-air damming can also be induced by a nearby low pressure system
(e.g., a tropical storm) in the right position with respect to the
coastline.

Atlantic Tropical Storm Marco (1990) was chosen for study because two
distinct incidences of coastal frontogenesis, cold air damming, and
orographic enhancement significantly alter the final precipitation
distribution. Marco was responsible for greater than 500 mm of
precipitation in parts of Georgia and South Carolina, although the storm
never reached hurricane intensity. Marco tracked northward slowly just
west of the Florida Peninsula, indicating a long period of geostrophic
upslope flow over the southern Appalachians. Therefore, it appears that
Marco's associated wind field led to the formation/enhancement of
mesoscale features which caused heavy precipitation and flooding during
the study period. Although the inland flooding associated with coastal
frontogenesis ahead of Marco most directly impacted Georgia and the
Carolinas, the physical processes responsible for the flooding can occur
anywhere along the East Coast in conjunction with a landfalling tropical
cyclone. Synoptic upper air analyses from NCEP\'s North American
Regional Reanalysis (NARR), NHC Best Track data, and hourly
high-resolution surface data will be used to explain how the coast\'s
topographic features combine with Marco to induce both occurrences of
the aforementioned mesoscale features and thus modify the total
precipitation distribution.

Heavy Rainfall Events Preceding the Arrival of Tropical Cyclones

Matthew R. Cote, Lance F. Bosart, and Daniel Keyser

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

Michael L. Jurewicz, Sr.

NOAA/NWS Weather Forecast Office, Binghamton, NY

During recent active Atlantic hurricane seasons, observational evidence
has suggested that heavy rainstorms sometimes can form unexpectedly well
in advance of landfalling and near-coastal tracking tropical cyclones
(TCs). The more extreme of these predecessor rain events (PREs) can
cause significant flooding with little advance warning and can have even
more serious implications if the TC itself later traverses the same
region and additional heavy rainfall occurs. The relative frequency of
PRE occurrence adds considerably to the forecast challenge prior and
subsequent to TC landfall. It is therefore imperative to increase
awareness in the meteorological community of the potential for PRE
formation and to study the underlying physical processes responsible for
when, where, and why PREs develop. The purpose of this presentation is
to provide a synthesis of the important synoptic-scale features
responsible for PREs with the major physical characteristics of PREs
themselves. Emphasis in this presentation is placed on the 2004 and 2005
hurricane seasons.

TCs during 2004 and 2005 associated with at least one PRE were
identified and analyzed using radar imagery from NCDC, NHC best- track
data, and NCEP/NARR gridded datasets. Precipitation data obtained from
the NPVU online QPE archive and NWS text products gleaned from online
data sources were used to approximate how much rain fell during each
TC/PRE event. Each TC examined showed some evidence of a peripheral
moisture surge into the PRE, and each associated PRE produced 24-h
normalized rainfall amounts of greater than 100 mm. A detailed data
catalog was created to establish some general characteristics of each
PRE.

A comparison of the PREs with a null case (Cindy 2005) showed that the
Bosart and Carr (1978) schematic model of antecedent heavy rain
occurring in a mid- and upper-level jet-entrance region confluence zone
well downstream of Hurricane Agnes (1972) was somewhat applicable to the
PRE cases. \"Typical\" PREs are located \~1000 km ahead of the parent
tropical system, occur 1-2 days prior to the arrival of the TC at the
latitude of the PRE, and last for \~12 h. Similarly, PREs are directly
related to overall TC activity and have a strong tendency to form left
of the eventual TC track. Frequency distributions and maps from selected
cases will be presented to demonstrate these points.

**A Climatology of Tropical Transition**

R. McTaggart-Cowan, L. F. Bosart and C. A. Davis

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

The importance of baroclinic forcings on tropical cyclogenesis has been
a topic of investigation for several decades; however, few studies have
quantitatively addressed the question, "what fraction of tropical
cyclones form from extratropical precursors?". This climatology of the
tropical transition (TT) genesis mechanism is based on our current
understanding of the TT process and represents an attempt to analyze the
importance of this genesis pathway to the overall tropical cyclone (TC)
population.

Two distinct classes of TT have been identified in recent studies.
Strong extratropical cyclone (SEC) TTs are characterized by the presence
of a strong, pre-existing lower level vortex of extratropical origin of
sufficient strength to trigger a wind-induced surface heat exchange
(WISHE) process (near-surface azimuthal wind speeds on the order of 10
ms^-1^). Initially, the presence of an upstream midlatitude trough --
responsible for the development of the extratropical vortex -- induces
vertical shear values that preclude tropical development despite its
passage over warm sea surface temperatures. However, as surface fluxes
warm and moisten the boundary layer, extensive deep convection generates
upper level outflow and redistributes potential vorticity in the
vertical so as to minimize shear above the lower tropospheric system.
Within this cocoon of low shear, midlevel convective warming leads to
the development of an elevated warm core and the system's development
thereafter follows a more traditional tropical trajectory. In contrast,
the weak extratropical cyclone (WEC) TT pathway focuses on the
concentration of convection by a precursor system that is too weak to
trigger the WISHE process. Once an enhanced region of deep convection is
established, the WEC TT proceeds in a manner similar to its strong
counterpart.

In this study, we quantify this conceptual model of TT in order to
develop a dynamically-based objective TT index. This is a necessary step
in the development of a TT climatology, and itself yields insight into
the classifications of WEC, SEC and more traditional tropical
development pathways. The active 2005 Atlantic hurricane season is used
as a training dataset in which the objective index is compared with
subjective analyses of the individual storm development mechanisms.
Thereafter, a climatology for all named storms from 1948 to 2004 is
undertaken using data from the NCEP/NCAR Reanalysis dataset. The results
of this study show that tropical systems formed along the TT pathway
comprise approximately 25% of the total tropical cyclone population,
suggesting that this development mode is important to the climatology.
Moreover, there is a clear tendency for systems that form as TT events
tend to be weaker and shorter-lived than those that develop in along
tropical trajectories. This has much to do with both the geographical
location of the TT events -- which tend to occur at higher latitudes --
as well as the sheared environment that resulting tropical cyclones
encounter. A suite of composite-based analyses identify the importance
of midlatitude features to a significant portion of tropical
developments and lifecycles.

Mesoscale Precipitation Structures Accompanying Landfalling and
Transitioning Tropical Cyclones in the Northeast United States

Jared R. Klein, Lance F. Bosart, and Daniel Keyser

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

David Vallee

NOAA/NWS Weather Forecast Office, Taunton, MA

Landfalling and transitioning tropical cyclones (TCs) can result in
heavy rainfall and dangerous flash flooding events over the Northeast
US. Complex mesoscale features found in these storms not only have
exacerbated flash flooding on smaller scales, but have provided an
important forecast challenge. An assumption underlying this research is
that the knowledge gained from a better understanding of the physical
processes controlling TC-related rainfall in the presence of complex
terrain has the potential to be applied to the long-term benefit of
operations. Accordingly, the purpose of this presentation is to present
the results of an ongoing investigation of how the observed mesoscale
distribution of heavy rainfall in landfalling and transitioning TCs is
modulated by the interactions of mesoscale and synoptic-scale features
in the presence of the complex physiography of the northeastern US.

A 67-storm (1950-2006) dataset of landfalling and transitioning TCs that
produced storm-total rainfalls of at least 10 cm provided by David
Vallee was used to identify candidate storms for our analyses. The
synoptic and mesoscale characteristics of the 16 most recent storms from
this dataset (2000-2006) were determined by constructing analyses of
daily rainfall (1200 UTC to 1200 UTC) from the NCEP Unified
Precipitation Dataset (UPD) for pre-2004 cases, the 3 h NCEP North
American Regional Reanalysis (NARR) dataset, and hourly archived surface
data. NCDC-archived radar imagery, NCEP/HPC analyzed precipitation maps,
and the NHC best-track TC dataset also were used to investigate these
cases. Selected surface and upper-air maps were constructed to identify
and categorize certain synoptic and mesoscale characteristics for each
case.

Preliminary results show that enhanced ascent associated with coastal
frontogenesis and/or orographic lifting provided a mesoscale focus for
heavy rainfall that tended to occur to the left of the storm track in
many of the cases. The interaction between a landfalling and
transitioning TC, an advancing upper-level trough, and a pre-existing
mesoscale boundary (e.g., a coastal front) or synoptic-scale front
occurred in almost every recent heavy rainfall case examined. In some
landfalling and weakening TCs that experienced minimal extratropical
transition, corridors of very heavy rainfall were noted to the right of
the storm track in conjunction with training convective storms.

**Warm-Season Lake-/Sea-Breeze Severe Weather in the Northeast**

Patrick Wilson, Lance Bosart, and Daniel Keyser

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

Tom Wasula

NOAA/NWS Weather Forecast Office, Albany, New York

Thunderstorms that form along lake- and sea-breeze convergence zones
over the Northeast sometimes are observed to become severe when they
migrate from their source regions. These thunderstorms can pose a
significant forecast challenge because they typically form under
conditions of weak synoptic-scale forcing. The dynamical and
thermodynamical processes, modulated by physiographic effects, that are
responsible for creating severe weather from lake- and sea-breeze
convergence zones are discussed through selected case studies. The
results from these case studies will be shown during the presentation.

Ten cases were selected for analysis. The NCEP/NARR gridded datasets,
along with data from radar, soundings, and surface observations, were
used to construct the analyses. These cases were divided into two
classes: pure cases where lake- and sea-breeze convergence zones were
primarily responsible for initiating severe weather in the apparent
absence of synoptic-scale forcing, and mixed cases where synoptic-scale
forcing acted in conjunction with mesoscale forcing from the lake and
sea breezes to generate severe weather. The 10-case sample includes a
null event where the arrival of marine air from a sea breeze suppressed
convection.

Pure cases were characterized by the absence of significant
synoptic-scale forcing. Typically, pure cases featured: 1) a ridge axis
at the surface or aloft, 2) temperatures (dewpoints) of at least 30°C
(20°C) in the planetary boundary layer with ample heat and moisture to
provide instability, and 3) weak flow with weak unidirectional wind
shear. In contrast, mixed cases typically featured: 1) a trough at the
surface or aloft, 2) boundary-layer temperatures ranging from 20°C to
30°C with dewpoints approaching but not exceeding 20°C, and 3) stronger
flow and stronger wind shear than in the pure cases. Perhaps the most
essential general finding for all cases was the prevalence of multiple
synoptic and mesoscale boundary intersections. These boundary
intersections served as locations where convergence and lift were
enhanced to the point where deep convection was initiated.

**Derecho Formation, Evolution and MCS Interactions During BAMEX**

Nicholas D. Metz and Lance F. Bosart

Department of Earth and Atmospheric Sciences

University at Albany, State University of New York

The purpose of this presentation is to take advantage of an active deep
convection period during BAMEX to provide a detailed assessment of the
formation and evolution of derechos and their interactions with other
mesoscale convective systems (MCSs). The first week of July 2003 (last
week of BAMEX) featured twelve coherent MCSs progressing across the
upper Midwest. Three of these MCSs met the derecho criteria and two are
of interest here (4-5 July and 5-6 July 2003). A 20-25 knot anomalous
200 hPa jet stream was present throughout the week across the northern
United States. A strong upstream blocking ridge in the eastern Pacific
contributed to the favorable synoptic set-up for derechos, along with a
persistent potential vorticity (PV) tail located immediately upstream of
the formation of each derecho. Derecho development was assisted by
transient upper-level shortwave disturbances along the PV tail that
provided a source of lift, a favorable configuration of lower-level and
upper-level jets, steep mid-level lapse rates, strong surface heating,
deep layer shear in excess of 40 knots, and large values of
surface-based CAPE.

The convective development of the two derechos was intertwined with two
less severe MCSs. The earlier 4-5 July derecho formed to the south of a
weak cyclone and resulted in the development of a quasi-stationary
surface boundary in Iowa and Illinois along the southern edge of its
significant cold pool. Radar imagery showed this derecho remained robust
as it crossed Lake Michigan despite cool water temperatures, weakening
only as it progressed further eastward of favorable jet support and
low-level moisture. A less severe MCS subsequently collapsed in the
derecho's cold pool. Gravity waves and an outflow boundary moved
eastward following the MCS's convective demise and interacted with the
quasi-stationary boundary, inducing a second MCS near the southern tip
of Lake Michigan. At the same time, the 5-6 July derecho progressed
eastward along a similar path across Iowa as the first derecho. The cold
outflow in the wake of this second derecho reinforced the cold pool and
quasi-stationary boundary left behind by the first derecho. This derecho
moved eastward, merging with the gravity wave-induced MCS. The combined
system weakened as it crossed the Great Lakes, moving eastward of the
most plentiful moisture and jet support.

**Using Ensemble Probability Forecasts And High Resolution Models**

**To Identify Severe Weather Threats**

Josh Korotky

NOAA/National Weather Service, Pittsburgh, Pennsylvania

Richard H. Grumm

NOAA/National Weather Service, State College, Pennsylvania

High resolution model data (NAM-WRF) and Ensemble Prediction System
(EPS) data from the National Centers of Environmental Prediction's
(NCEP) Short-Range Ensemble Forecast System (Du et al. 2004:SREF) are
used to predict areas with a severe weather threat. This study
illustrates the complimentary roles of high resolution model and EPS
forecasts, and demonstrates the value of using SREF forecast products
that depict probabilities of exceedance and joint probabilities of
variables related to severe weather. Probabilities of exceedance for
Convective Available Potential Energy (CAPE), Storm-Relative Helicity
(SRH), height normalized (mean) shear, and the Energy Helicity Index
(EHI) are examined. Joint probabilities of CAPE, effective shear, and 3
hr. convective precipitation are also considered.

NAM WRF forecasts and SREF probability forecasts are examined for a
vigorous severe weather event that occurred across much of the central
Mississippi and lower Ohio Valleys on 2 April 2006. This presentation
will demonstrate that joint and exceedance probabilities from the SREF
make it possible to clearly distinguish areas with the greatest severe
weather potential.

A forecast strategy is proposed which utilizes *1)* ensemble data for
assessing the likelihood, mode, and forecast confidence of a severe
weather event; *2)* climatological anomalies for evaluating the
historical context of an impending event; and *3)* high resolution model
data for determining the magnitude of moisture, the horizontal and
vertical extent of moisture, important mesoscale structures, and
relevant forcing mechanisms.

**The 4 August 2004 Central Pennsylvania Severe Weather Event -
Environmental and Topographic Influences on Storm Structure Evolution**

Joseph P. Villani

NOAA/NWS Weather Forecast Office, Albany, New York

Severe thunderstorms moved across portions of central Pennsylvania
during the late afternoon and early evening of 4 August 2004. Initially,
the thunderstorms caused straight-line wind damage in the Central
Mountains and Middle Susquehanna Valley, and then evolved into tornado
producing thunderstorms across the Lower Susquehanna Valley in and
around the Harrisburg metropolitan area. Several significant radar
features were observed, with most of the severe thunderstorms exhibiting
bow echo characteristics. Some storms developed mesocyclones and
consequently spawned tornadoes in the Lower Susquehanna Valley. The
intensities of the tornadoes were F0 or F1, and resulted in downed trees
and structural damage to homes.

The severe thunderstorms developed in a moist and moderately unstable
atmosphere across western Pennsylvania early in the afternoon, as an
upper level short wave trough moved eastward through the Ohio Valley. A
frontal boundary across northern Pennsylvania separated cloudy and cool
conditions to the north from warm and humid conditions to the south.
Daytime heating with temperatures near 30^o^C and surface dewpoints
around 20^o^C resulted in surface based Convective Available Potential
Energy (CAPE) values reaching 1000 to 2000 Joules per kilogram (J/kg).
The vertical wind shear was unidirectional across western and central
Pennsylvania with westerly flow aloft, which contributed to the linear
mode of the convection. Across the Lower Susquehanna Valley low level
winds backed to a south to southeast direction in response to a weak
surface low pressure center moving eastward across the region.
Additionally, the topography of the area likely enhanced the development
of the low level southerly wind component, which resulted in sufficient
low level directional wind shear for tornadogenesis to occur.

This presentation will first focus on interrogating radar imagery from
(KCCX) State College and (KLWX) Sterling to examine the significant
features associated with the severe and tornadic thunderstorms. The
focus will then shift to discussing factors that contributed to the
convective mode transitioning from straight-line wind producing storms
to tornadic, as they moved southeast into the Lower Susquehanna Valley.

**Northern New England Coastal Flooding**

John W. Cannon

NOAA/National Weather Service Forecast Office, Gray, Maine

Forecasting storm surge and coastal flooding raises complex issues along
the Maine and New Hampshire coastline. The bathymetry and the irregular
configuration of the northern New England coast allows for a large range
of atmospheric and tidal conditions through localized channeling effects
of wind and water. Access to real-time tide data is limited to a single
point in Portland Harbor, which is problematic when forecasting over a
large, data-sparse coastline. Storm surge guidance is available, but can
have large predictive and temporal errors. These challenges exist while
the population continues to increase near vulnerable beaches. Storms
pose a risk to millions of dollars in personal property damage and
significantly impact the marine community.

Traditionally, forecasters base flood warning decisions for long
stretches of coastline on the 12 foot flood benchmark at the Portland
Harbor tide gauge. However, in an effort to better understand and
predict a wide range of tide levels associated with coastal flooding, a
coastal flood database was created for the period 1914 to present for
Maine and New Hampshire using Storm Data Publication
([http://www.ncdc.noaa.gov](http://www.ncdc.noaa.gov/)[)]{.underline}.
This coastal flood catalogue was compared to tide archives for Portland
Harbor ([http://tidesandcurrents.noaa.gov)]{.underline}. A coastal flood
climatology was then created using the predicted versus observed tide
levels. Storm tracks were then examined
(<http://www.hpc.ncep.noaa.gov/dwm/dwm.shtm>) to identify predominant
wind flow during coastal flood events.

The coastal flood climatology will be presented. The climatology
suggests coastal flooding occurs in multi-year clusters, while moderate
to severe flooding events are rare. Coastal flooding occurs over a wide
variety of tide heights in Portland Harbor, as large ocean waves or
freshwater flooding occasionally offset modest tidal surges. They are
predominantly cold season events with a prevailing northeast wind. The
peak observed storm tide usually occurs several minutes prior to the
predicted astronomical high tide. Finally, unusual and extreme cases
will be shown, such as the October 1996, October 1998 and May 2006
coastal flood events which were coincident with freshwater flooding.

**A Flash-Flood Climatology for the**

**National Weather Service Eastern Region**

Alan M. Cope

NOAA/Number range CHAPTERNational Weather Service, Mount Holly, New
Jersey

A climatology of flash flood events has been developed for the National
Weather Service Eastern Region (NWS-ER). Data for flash flood events
from 1996 through 2005, for all 23 NWS-ER forecast offices, were
obtained from the NWS Verification/Storm Data \"Stats on Demand\" web
site. The data, stratified by time of day and time of year, were
examined for the entire NWS-ER, and also for four \"sub-regions\": New
England, mid-Atlantic, Ohio Valley, and South.

Results showed that flash flood frequency varied greatly around ER, from
over 100 events per year in the Pittsburg area, to less than 10 per year
around Caribou ME and Columbia SC. Almost half (47%) of events occurred
in June July or August, and over two-thirds (71%) fell in the warm
season of May through September. Diurnally, over half the events (51%)
occurred during the period 1900 to 0300 UTC (3pm to 11pm EDT). This
diurnal distribution was most pronounced during summer. Seasonal
distribution varied somewhat by sub-region, with the Ohio Valley peaking
earlier and the South later, while the diurnal distribution looked
fairly similar for all four sub-regions.

To further study summertime flash floods, synoptic meteorological
conditions were examined for 15-20 significant flash-flood days (10 or
more events) in each sub-region during June July and August. Days with
named tropical systems were excluded. Composite mean and anomaly charts
were created from NCEP/NCAR Global Re-analyses and from the NCEP North
American Regional Re-analyses, accessed via NOAA/ESRL web-based
interfaces. Variables included pressure-height, zonal and meridional
winds, temperature and specific humidity.

The resulting composites show mainly positive anomalies in moisture and
meridional wind and negative anomalies in pressure-height, although
there are some interesting exceptions. Synoptic patterns such as surface
low pressure, mid-level troughs and upper-level jet streaks, are most
similar for the New England and mid-Atlantic sub-regions, somewhat
similar but generally weaker for the South, but distinctly different for
the Ohio Valley. The pattern differences among ER sub-regions will be
illustrated and discussed further at the meeting, as well as the ER-wide
results mentioned above.

**Number range CHAPTERGIS Applications in Meteorology and Hydrology**

John S. Quinlan

NOAA/National Weather Service, Albany, NY

Geographic Information Systems (GIS) are systems of hardware and
software which store, retrieve, map, and analyze geographic data in
relational databases. GIS uses spatial and attribute data with vector
and raster data structures, and topology to create geographic data
models. This allows the user to spatially analyze and display in a
format which can more easily be understood and shows interrelationships
that otherwise may not be apparent. GIS also allows for the
representation of a third dimension which is usually elevation. The
Digital Elevation Model (DEM) produced by the National Mapping Division
of the United States Geological Survey (USGS) is the GIS representation
of continuous elevation values over a topographic surface by a z-axis,
referenced to a common datum. DEMs are typically used to represent
terrain relief. Use of ESRI's Spatial Analyst extension in GIS allows
for the study of locations and shapes of geographic features and the
relationships between them. It is very useful for analyzing
meteorological or hydrologic data in terms of geographic distribution,
and for verification analyses of forecasts and warnings.

Many GIS projects have been conducted from 2000-2005 and range from
verification of weather forecasts and warnings to use of GIS analyzed
data in flood warnings. It will be shown how GIS should be a main
component of each National Weather Service Forecast Office's (NWFO)
warning verification program, and how GIS can be used to improve
forecast and warning operations by giving the forecaster spatial
analyzes of their forecasts and warnings. Examples of this which will be
presented include variability of snow to liquid ratios during winter
weather events and how this variability can be applied to improving snow
forecasts, analyses of snow survey data and the use of snow density and
basin average snow water equivalent in flood warnings and Winter/Spring
Flood Outlooks, and a GIS analysis of 30-year climatic normals to
determine the start of the growing season.

**The June 2006 East Canada Creek Flood -- Forecasting a Record Category
Flood in the Absence of Real-Time Gage Data.**

Robert C. Kilpatrick

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

The East Canada Creek, and in particular, the Village of Dolgeville, has
long been known to have a potentially severe flood problem. A severe
flood occurred there in October 1945, and other significant floods have
occurred in March 1913, December 1984, January 1996, January 1998, and
May 2000. WFO Albany became aware of this risk of flooding a number of
years ago.

Over several years procedures were developed and refined, to make river
forecasts for sites, such as Dolgeville, where adequate real-time data
and guidance are not available. On 25-27 June 2006 five to ten inches of
rain fell over the Mohawk Valley and Western Adirondacks. These forecast
procedures were used with the Multisensor Precipitation Estimate (MPE)
from the KENX WSR-88D and the WFO Hydrologic Forecast System (WHFS), in
the early morning hours of 28 June to produce a stage forecast for the
East Canada Creek of a little over 15 feet around noon that day.

No real-time gage readings were available. The forecast was used to
issue a record category flood warning with about four hours of lead
time. The forecast was about a foot too low based on measurements made
by USGS at a site about 8 miles downstream. Without these methods a
forecast of the height the East Canada Creek would not have been made,
nor could the severity of the resulting flood been forecast. The height
measured by USGS after the event was about two feet higher than the
previous flood of

record.