Kirk Apffel
NOAA/ National Weather Service
Gray, ME

ABSTRACT

Wind forecasts are critical to commercial and recreational boaters in the Gulf of Maine. Forecasters at the National Weather Service (NWS) office in Gray, Maine noted several cases where northeasterly wind forecasts were poorly forecast. Improving these forecasts can help mitigate property damage and prevent loss of life.

Wind speed and direction data was collected for 3 buoys in the Gulf of Maine from January 1, 2004 to June 30, 2005. Forecast data was collected for ETA, Global Forecast System (GFS), GFS Model Output Statistics (MOS), Western North American Wave Model (WNA), and official NWS wind forecasts. These data were compared to the observed wind speed and direction. Mean absolute error and bias were calculated for each wind direction on an 8-point compass.

Results showed the largest mean absolute error in numerical model guidance was in a northeasterly flow. In order to examine the source of this error, a sample of northeasterly wind flow cases was identified. Events were defined as all three buoys with a wind direction between 15 to 75 degrees at the forecast verification times of 06 UTC and 18 UTC. To stratify the synoptic regime, surface maps were collected and divided into a cool season sample, including November through April, and a warm season sample, including May through October. This yielded 24 cool season cases, and 50 warm season cases. Composite maps for each season were compiled for each model forecast, indicating the short term forecast bias of each case. Positive and negative biases were defined as a mean absolute error greater, or less than, 5 knots, respectively, or neutral if the error was less than 5 knots.

Verification results of model guidance will be presented, stratified by wind direction. In addition, composite surface maps will show that numerical guidance tended to under-forecast northeasterly winds when the surface low was south or southwest of Cape Cod in the cool season. This bias did not exist when the surface low was east of Cape Cod.

Lance Bosart
Department of Earth and Atmospheric Sciences
University at Albany/SUNY/ES-351
1400 Washington Avenue
Albany, New York 12222
E-mail: bosart@atmos.albany.edu Phone: 518-442-4564 Fax: 518-442-4494

ABSTRACT

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 document the environment in which the cyclone formed, to illustrate its mesoscale structure and evolution, and to compare and contrast its development to hurricanes.

Jim Brewster
NOAA/ National Weather Service
Binghamton, NY

ABSTRACT

In winter, intense snow showers, often termed "snow squalls" are associated with the passage of surface frontal boundaries or troughs of low pressure, and are common to the Northeastern United States. Snow squalls pose a significant, short-term forecast problem for meteorologists concerned with public and aviation safety. Although snow squalls are not known for heavy snow accumulation, they do typically produce heavy snowfall rates, very poor visibility, and enough of a snow accumulation to wreak havoc on travelers as they pass through an area.

The Wintertime Instability Index (WINDEX) method for assessing the synoptic environments favorable for snow squalls was developed in 1993. This legacy technique was developed during an era when only a limited subset of parameters from the Nested Grid Model (NGM) was routinely available to operational forecasters. These parameters were related to moisture, low level instability, surface and upper level forcing. The method was modified in 2005 to take advantage of the much larger suite of forecast data currently available on a routine basis to National Weather Service (NWS) forecasters. The updated technique now incorporates higher resolution, point specific, numerical model data via the NWS Buffalo's Forecasting Toolkit (BUFKIT) thermal profile analysis software.

Two events, February 17, 2005 and November 24, 2005 (Thanksgiving Day), were examined using the WINDEX method. These events were chosen due to their significant, negative impact on late afternoon and evening travel in the Binghamton, NY and Scranton, PA areas on the dates noted. Upper level and surface synoptic charts, radar and satellite imagery, and plan views of the North American Mesoscale Model (NAM) forecast output were examined for each case, and will be used to lay the synoptic groundwork for each event. The specific WINDEX criteria were analyzed from hourly forecast soundings via the BUFKIT software, and tabular model output from the NAM. Forecast lapse rate data between 950 and 800 hPa for the two cases was examined, as these levels correlate best to the T1 and T5 sigma levels from the NAM model output parameter used in the current WINDEX method.

This presentation will outline the WINDEX method, and then demonstrate it's effectiveness on short term forecast and warning operations at NWS Binghamton, NY on February 17, 2005, and Thanksgiving Day 2005. The hourly forecast lapse rate data prior to the development of the snow squalls will be examined, and recommendations for using the lapse rate forecast data in lieu of the legacy T1 and T5 differential will be presented.

Jonathan Arielle Forest Byrne
Consulting Meteorologist
Cambridge, MA
Phone: (617) 279-6162
E-mail: jbyrne@willowhillschool.org

ABSTRACT

Historically, synoptic scale cyclones are classified according to two prevailing paradigms 1) Extratropical cyclones composed of a baroclinic environments coupled with frontal dynamics that rotate counterclockwise (in the northern hemisphere) around a cold core low pressure center at the earth's surface, supported by a trough of varying wavelength and amplitude within the middle and upper layers of the troposphere. Extratropical cyclones derive kinetic energy primarily from symmetric instability, jet stream infusion within middle and upper layers of the troposphere, coupled with horizontal mass flux and divergence, and sensible and latent heat fluxes (The latter effect especially in the case of coastal and oceanic cyclones.2) Tropical cyclones composed of a barotropic environments that rotate counterclockwise around a warm core low pressure center. Tropical cyclones derive kinetic energy principally from sensible and latent heat fluxes associated with minimum tropical ocean surface temperatures of at least 27 degrees Celsius, mid tropospheric ventilation, and external anticyclonic forcing.

This presentation will propound a hypothesis for a third classification scheme for synoptic scale cyclones defined by a cross section of the two prevailing paradigms for extratropical and topical cyclones. This third classification, hence referred to as "super-hybrid cyclones" is in turn divided into two categories 1) Super-hybrid cyclones that have undergone a baroclinic transition from tropical cyclones 2) Super-hybrid cyclones that result directly from explosive extratropical cyclogenesis and rapid spin up especially within marine environments. The presentation will begin with the reading of a brief essay written by the author.

Northern New England Coastal Flooding

Jessica Cox, R. Stewart, C. Lin
McGill University, Montreal, QC
E-mail: jessica.cox@mail.mcgill.ca

ABSTRACT

The current practice of snowfall forecasting in Canada is to determine the snow water equivalent (SWE) expected to precipitate using a numerical weather predication model and then multiplying this amount by a snow/SWE ratio to determine the forecast snow depth. The 10:1 "rule of thumb" is still widely used operationally as this snow/SWE ratio, even though it is well-known to introduce error in the forecasts due to the highly variable density of snow. The objectives of this study are to explore the behaviour of snow/SWE ratio by developing a Canada-wide climatology of this quantity and examining the performance of an experimental Meteorological Service of Canada forecast algorithm over the winter 2004-2005 using several verification techniques.

Jason M. Cordeira and Neil Laird
Department of Earth and Atmospheric Sciences, University at Albany, Albany, NY
Department of Geoscience, Hobart and William Smith Colleges, Geneva, NY

ABSTRACT

General meteorological intuition suggests that the development of lake-effect systems is inhibited when lakes are extensively ice covered. A recent investigation using visible satellite imagery found several events where lake-effect clouds developed over regions of the Great Lakes having ice concentrations exceeding 80% over the entire lake. Recent observations have shown that lake-effect snowstorms can occur with widespread ice coverage; however the impact of ice cover on these events has not been examined despite its noted importance to winter weather forecasting in the Great Lakes region.

The study to be presented examined two significant lake-effect snow events which occurred downwind of Lakes Erie and Ontario on 12-14 February 2003 and 28-31 January 2004. For each event, snowfall totals of more than 30 cm and 200 cm occurred along the shores of Lake Erie and Ontario, respectively, during time periods when Lake Erie had widespread ice cover and Lake Ontario was predominantly ice-free. The investigation utilized Great Lakes ice charts, MODIS satellite imagery, radar data, soundings, and surface observations.

The mesoscale evolution in snow band duration, intensity, and structure was similar in the vicinity of Lakes Erie and Ontario for both events. While an intense shoreline snow band occurred over Lake Ontario for the full duration of each event, the structure and intensity of the lake-effect snow bands varied in the vicinity of Lake Erie. The development, location and duration of lake-effect circulations were dependent upon conditions of wind direction, upwind moisture (lake-to-lake influences), and lake-ice concentrations. Lake Erie ice cover acted to alter fetch distances and consequently reduced surface heat fluxes. Bands therefore developed downwind of ice-free, low ice concentrations, and new (thin) ice regions. Further, collocation of shoreline bands and horizontal convective rolls downwind of Lake Erie at different times during the progression of both events resulted in locations of heaviest snow totals.

The presented research will focus on (1) the role ice coverage played in limiting the surface heat fluxes, (2) their subsequent impact on the development and strength of lake-effect mesoscale circulations near Lake Erie, and (3) a comparison of the evolution of lake-effect mesoscale systems over Lakes Erie and Ontario.

Paul Croft and Michael G. Stroz

ABSTRACT

Cool season severe weather occurrence in and near the Philadelphia National Weather Service in Mount Holly, NJ, County Warning Area while rare does pose a significant forecast challenge. While most wind events tend to be related to strong pressure gradients given the synoptic forcing common during the cool season, damaging wind events, as well as reports of hail and tornadoes associated with convective systems also take place. Although these are associated with progressive and/or intensifying weather systems they do not have a clear conceptual model for a forecaster to apply confidently in advance.

In an effort to better forecast the occurrence of these events a preliminary synoptic climatology was prepared to determine the associated synoptic features. The intent was to provide greater insight to the characteristic nature of these events, their associated attributes and patterns, and to provide some guidance as to what forecasters might look for in advance to recognize the potential for severe weather. In addition, it would assist in identification of what other work might be necessary to improve prediction and lead-time across such a major metropolitan area.

The study focused on local storm reports (obtained online from the Storm Prediction Center) for the months of October through March during the six year period 2000-2005. Preliminary results indicated that severe weather events occurred only one percent of all days included (for the dataset sampled) and these were dominated by damaging wind reports (80% of all local storm reports). Further examination of the events focused on their associated synoptic patterns as determined from the Daily Weather Map Series.

Results indicated three basic synoptic types driving the severe weather, two of which shared similar features and were dynamically driven. The third synoptic type was characterized by quasi-stationary frontal features and thus much more dependent upon localized thermodynamic forcing. This third synoptic type accounted for all of the hail reports and most of the tornado reports. The spatial distributions of the storm reports revealed little or no evidence of other local effects or population-biased reporting although frequencies were observed to be lower near the coast and in the Pine Barrens region of New Jersey.

Dorothy Durnford, John Gaykum. Eyad Attallah*,and Marco Carrera
Department of Atmospheric and Oceanic Sciences
McGill University
E-mail: suttonplace@sympatico.ca

ABSTRACT

Satellites provide uniform data coverage globally. Thus, their data have the potential to reduce analysis errors in data sparse areas significantly, thereby improving numerical weather prediction (NWP) forecasts. We describe a methodology to generate NWP model initial conditions (ICs) from satellite total column ozone data based on Davis et al. (1999). This methodology involves the following steps: 1) derive dynamic tropopause potential temperature (DTTH) field from total column ozone data using correlation coefficients and linear regression least squares best fit line parameters, 2) convert the 2-D DTTH field to a 3-D potential vorticity (PV) field, 3) invert the 3-D PV field to obtain model ICs (see Davis and Emanuel, 1991). The first two steps will be discussed. We find that the correlation coefficients vary distinctly with year, month, latitude and 10-degree longitude bin, but that strong correlation coefficients can be obtained despite ozone/DTTH time differences as great as seven hours.

Davis, C. A., and K. A. Emanuel, 1991: Potential vorticity diagnostics of cyclogenesis. Mon. Wea. Rev., 119, 1929-1953.

______, S. Low-Nam, M. A. Shapiro, X. Zou, and A. J. Krueger, 1999: Direct retrieval of wind from Total Ozone Mapping Spectrometer (TOMS) data: examples from FASTEX. Quart. J. Roy. Meteor. Soc., 125, 3375-3391.

Hurricanes and Climate Change

Kerry Emanuel
Program in Atmospheres. Oceans, and Climate
Massachusetts Institute of Technology
RM 54-1620 MIT
77 Mass Ave
Cambridge, MA, 023139
Phone: (617) 253-2462
E-mail: emanuel@texmex.mit.edu

ABSTRACT

The 2005 Atlantic hurricane season broke an astonishing number of records, including the most storms in any year and the most intense storm (in terms of central pressure) measured in the Atlantic, not to mention the greatest loss of life in many decades and the largest damage total by any reasonable normalized measure. Is this a statistical fluke, resulting from a combination of natural factors such as a neutral ENSO phase and the peak of the Atlantic multi-decadal mode, or is global warming contributing to the very high level of activity since 1995? I will review what the observations, models and theory have to say about this, with an eye toward the future.

Anthony R. Fusco*, Gregory G. Garner, and Eric G. Hoffman
Department of Chemical, Earth, Atmospheric, and Physical Sciences
Plymouth State University
Plymouth, New Hampshire

ABSTRACT

A major flooding event occurred on Columbus Day weekend of 2005 in southern New Hampshire, western Massachusetts, and central Connecticut. River flood gage information from the Ashuelot River showed that this flooding event was the one of the highest floods recorded by the instruments. Well over six inches of precipitation fell across southwestern New Hampshire in a twenty four hour period on 8 October 2005. Several meteorological factors combined to cause an extended period of moderate to heavy rainfall. A weak frontal boundary moved across New Hampshire and settled along the Atlantic coastline. Although the surface frontal boundary was east of the area, a strong temperature gradient occurred over southern NH at 850 mb. High amounts of tropical moisture and a wave of weak low pressure associated with the remnants of Tropical Storm Tammy moved north along the surface front. Weak warm advection associated with this system along with the influence of weak trough at mid-levels and upper level divergence associated with the equatorward entrance region of a jet streak over eastern Canada all contributed to strong rising motion. Topography may have also enhanced precipitation totals.

Tom Galarneau, Jr.* and Lance Bosart
University at Albany/SUNY
ABSTRACT

Warm season continental anticyclones are frequently associated with heat waves and drought. A less appreciated aspect of continental anticyclones is that mesoscale disturbances evident on the dynamic tropopause (DT; defined here as the 1.5 potential vorticity (PV) unit surface), known as .Ridge Rollers. (RRs), are often observed to circumnavigate the periphery of these anticyclones. RRs often originate as fractures from the equatorward ends of northeast-to-southwest oriented PV tails and subsequently move westward along the equatorward periphery of upstream anticyclones. These RRs then move poleward and eastward around the upstream and poleward periphery, respectively, of the anticyclone. RRs may interact with other subsynoptic-scale disturbances on the poleward periphery of the anticyclone that originated from the upstream westerlies.

RRs may be associated with convection along the anticyclone periphery with organized mesoscale convective systems (MCSs) occurring on the poleward periphery where the aforementioned upper-level westerly flow, and associated jet-entrance region, provides enhanced ascent and deep-layer wind shear. Limiting factors include the state of atmospheric stability, positive convective available potential energy (CAPE) versus zero CAPE, and the presence (or absence) of a moist planetary boundary layer (PBL).

The purpose of this presentation is to document and compare and contrast the structure and evolution of heat wave-producing anticyclones over the US and Australia during July 1995 and February 2004, respectively. Particular attention will be paid to the behavior of RRs and their impact on convective initiation and mode along the periphery of these anticyclones.

Richard P. Giard*, Kate L. Morgan, Matthew T. Flader, and Eric G. Hoffman
Department of Chemical, Earth, Atmospheric, and Physical Sciences
Plymouth State University
Plymouth, New Hampshire

ABSTRACT

The 2005 Atlantic basin hurricane season was unprecedented in activity, intensity, duration, and destruction. When compared objectively with seasonal statistics logged over the past 120 years, this was a year like no other. The 2005 Atlantic Hurricane season saw a record-setting 27 named storms, requiring the use of Greek alphabet storm names for the first time in history. Of the 27 named storms, 14 were hurricanes of which 7 were intense. This season featured the costliest hurricane on record; the lowest pressure yet recorded in the Atlantic basin; and three category 5 hurricanes.

The 1995 Atlantic hurricane season was also extremely active, with 19 named storms; 11 hurricanes; and 5 intense hurricanes. However, a direct statistical comparison of the 2005 and 1995 seasons reveals that 2005 was significantly more active. Furthermore, during 2005 the development regions and tracks of storms were distinctly different than in 1995, and storms typically lasted longer and were stronger overall.

This study aims to identify, interpret, and contrast the complex, interrelated meteorological conditions that influenced the characters of these two benchmark tropical seasons. An effort is made to determine why the 2005 season was so exceptional.

Landsea et al. (1998) identify several environmental factors that appear to have contributed to the active 1995 season. These factors include a La Nina phase of the El Nino/Southern Oscillation (ENSO); below-normal average sea level pressure (SLP); above-normal average sea surface temperatures (SST); above-normal average total precipitable water (TPW); below average vertical wind shear values; and an easterly phase of the quasi-biennial oscillation (QBO). These same factors were investigated for the 2005 Atlantic season of 1 June through 30 November 2005.

The results of this investigation show that these same environmental factors were comparable between 1995 and 2005. The lone exception was the QBO factor, which was in the westerly phase in 1995, but in the easterly phase in 2005. Thus, the validity of these factors as reliable indicators for above-normal tropical storm activity in the Atlantic basin is confirmed.

Matthew D. Greenstein*, Lance F. Bosart, and Daniel Keyser
Department of Earth and Atmospheric Sciences
University at Albany/SUNY
1400 Washington Ave., Albany, NY 12222
Phone: 518-442-3331
Fax:   518-442-4494
Email: greenstein@atmos.albany.edu, bosart@atmos.albany.edu, keyser@atmos.albany.edu

David J. Nicosa
National Weather Service
Binghamton Weather Forecast Office
32 Dawes Drive, Johnson City, NY 13790
Phone: 607-770-9531 ext. 223
Fax: 607-798-6624
Email: david.nicosa@noaa.gov

ABSTRACT

Cold-season frozen precipitation in the northeastern United States is manifest in a variety of spatial patterns evident on radar imagery. Although forecasters can predict likely areas of precipitation, considerable difficulty remains in properly identifying mesoscale precipitation signatures within the main precipitation shield. As viewed on a radar reflectivity image, precipitation can appear relatively uniform, fractured, banded, or as a combination of all three. In addition, the bands themselves can take on a number of forms. Being able to forecast such mesoscale precipitation characteristics is vital in adding value to a forecast by enhancing the mesoscale prediction of snowfall amount and variability. The purpose of this presentation is to examine the role of synoptic-scale and mesoscale forcings, upright and slantwise instabilities, and microphysics in determining the mesoscale structure and evolution of precipitation regions in Northeast winter storms.

Twenty .heavy snow. events in the Northeast from the winters of 2002.3 through 2004.5 have been selected for analysis. The .heavy snow. criterion is met if at least 15 cm of snow accumulates in 12 h over an area of ~15,000 km2 (approximately the size of Connecticut). High-resolution WSI NOWrad composite reflectivity radar mosaics are used to diagnose the character of the mesoscale precipitation patterns in each of the events. Using the NCEP North American Regional Reanalysis, appropriate horizontal and cross-sectional maps are created for each event in order to ascertain which parameters.quasi-geostrophic forcing, frontogenesis, slantwise and upright instability, and microphysics.can assist in determining the structure and evolution of the observed mesoscale precipitation patterns. For this presentation, relationships between the aforementioned parameters and the mesoscale precipitation patterns are presented. Lastly, a representative case study is included to demonstrate how the temporally changing parameters delineated above alter the mode of precipitation of one heavy snow event during its lifetime.

Eric P. Kelsey* and Lance F. Bosart
Department of Earth and Atmospheric Science
University at Albany/SUNY
1400 Washington Ave.
Albany, NY 12222
Phone: (518) 442-4574
E-mail: ekelsey@atmos.albany.edu

ABSTRACT

Dale was born as a tropical depression(TD)in the tropical northwestern Pacific Ocean on 2 November 1996 and dissipated three weeks later as an extratropical cyclone(EC)in northern Russia just south of the Kara Sea. Dale tracked westward around a subtropical high, became a typhoon on 6 November and then a supertyphoon (estimated peak at 140 kt) just before it turned to the northwest three days later. Dale recurved to the northeast around the east side of a strong polar vortex as it entered the influence of a strong subtropical westerly jet and underwent extratropical transition(ET)over the Bering Sea. Dale rapidly reintensified into a powerful EC as it turned northwestward toward Siberia and slowly died as it moved westward along the north coast of Russia. This presentation will focus on the synoptic scale aspects of Dale's life cycle with emphasis on noteworthy aspects that include: 1) environmental sea level pressure perturbations of 12 hPa in 10 days over the tropical western Pacific during genesis, 2) the relationship between Dale and a powerful 200 hPa East Asian jet during ET, and 3) a surge of modified tropical air ahead of Dale that crossed the North Pole and reached northern Greenland during the EC phase.

ECMWF ERA-40 2.5 gridded reanalyses were used for diagnostic calculations. Joint Typhoon Warning Center (JTWC) best track and intensity estimates were obtained for Dale during its tropical phase. Ship reports from the Comprehensive Ocean-Atmosphere Data Set were used to refine Dale analyses during its lifetime.

Results indicate that two mesoscale convective vortices (MCVs) were initiated in the tropical northwestern Pacific by two upper-tropospheric potential vorticity (PV) anomalies. The entrance regions of two tropical thermal jets combined to create strong upper-level divergence that helped lead to the organization of the MCVs into TD Dale. Dale interacted with a strong westerly jet and an upper-tropospheric PV anomaly embedded within the jet on 13 November. This interaction led to the ET of Dale within a highly baroclinic environment (winds exceeded 100 m/s in a 200 hPa jet streak ahead of Dale) and resulted in a strong poleward flux of modified tropical air ahead of the storm. This poleward flux of modified tropical air ahead of Dale led to a further amplification of a preexisting downstream ridge toward the North Pole. As Dale crossed the strong jet axis explosive reintensification occurred as attested by a central pressure decrease of 38 hPa in 48 hours on 13 and 14 November to about 943 hPa. The 1000-500 hPa thickness over the North Pole increased 30 dam to 532 dam in 24 hours on 16 November as the modified tropical air crossed the Pole. While still a strong storm, Dale tracked north to 82oN then turned west along the north coast of Russia before finally dissipating on 22 November.

Dr. Kevin Kloesel
Assistant Dean, College of Atmospheric and Geographic Sceinces, OU
Adjunct Associate Professor, School of Meteorology, OU
Director of Outreach, Oklahoma Climatological Survey

ABSTRACT

This icebreaker session is designed to foster an awareness of the performance of the severe weather warning process in select meteorological disasters in our history. The presentation will be interactive, and focus on the societal expectations of the warning process, and the difficulty in communicating highly technical information to a lay public that is slipping in math and science literacy. Service Assessments and Natural DisasterSurvey Reports from the National Weather Service will be used to put the public's use of weather information into a historical context. In addition, the current trend to include sociological and demographic information into the warning process will be highlighted, as well as the relevance of research on how adults and children learn about scientific topics. The presentation will conclude by exploring a myriad of products that are currently available for public use, and the audience will be asked to participate in the assessment of the utility of these products in conveying risk in severe weather situations.

Neil F. Laird*, Helen Carr*, and Ryan Sobash
Department of Geoscience, Hobart & William Smith Colleges, Geneva, NY
Department of Meteorology, Penn State University, State College, PA

ABSTRACT

Much of the current knowledge regarding lake-effect snow storms has been developed through investigations of systems associated with large water bodies, such as the Great Lakes and the Great Salt Lake. Lake-effect snowfalls and mesoscale circulations associated with small lakes, with fetches less than 40 km, have received less attention. Significant snowfall totals have been observed with these mesoscale lake-effect events although the spatial scale of these systems is smaller than those that develop over larger lakes. The Finger Lakes region of New York State(NYS) harbors a collection of small lakes with differing sizes which produce lake-effect snow systems. This observational study provides a unique examination of the frequency, spatial distribution, intensity, and conditions favorable for lake-effect systems associated with these small lakes. Previous investigations of NYS Finger Lakes snow events have used mesoscale models to examine a limited number of cases. The current study used Binghamton, NY WSR-88D radar data to examine lake-effect events for the winters (October . March) of 1995 through 2004. Events were separated into two classifications; lake-effect and lake enhanced. Lake-effect events developed over and downwind of a lake and were not associated with larger-scale systems. Lake enhanced events occurred when previously existing precipitation systems were noticeably enhanced in the vicinity of the lakes. Two types of lake-enhanced events were discovered. The first type occurred in association with synoptic-scale systems. The second type occurred in association with pre-existing lake-effect snow bands originating from Lake Ontario. Several notable lake-effect and lake-enhanced events will be presented.

Andrew N. Loconto and James P. Koermer
Dept. of C.E.A.P.S.
Plymouth State University
Plymouth, NH

William P. Roeder
45th Weather Squadron
Patrick Air Force, Florida

ABSTRACT

Cape Canaveral Air Force Station (CCAFS) and Kennedy Space Center (KSC) are located in "lightning alley" of the United States. After lightning advisories, convective winds from thunderstorms are the second most frequent warning issued by the 45th Weather Squadron. The long lead-times and precise speed thresholds of these convective wind warnings make them an extreme challenge to forecast. A NASA Space Grant was awarded to develop a climatology of convective winds at CCAFS/KSC as a first step in improving the convective wind warnings at these locations. Nine years of wind observations for May through September from over 40 towers covering the CCAFS/KSC and surrounding areas were analyzed to develop an updated convective wind climatology. The peak wind data were first subjected to extensive automated and manual quality control. Strong wind episodes were deemed convective through reviews of archived satellite, radar, lightning, and KTTS surface observations. Additionally, surface analyses were used to assess potential pressure gradient contributions to the stronger outbreaks and to eliminate tropical cyclone-driven events. Climatological assessments will include breakouts by year, month, time-of-day, and tower elevation. Preliminary results will be presented.

Nicholas D. Metz* and Lance F. Bosart
Department of Earth and Atmospheric Science
University at Albany/SUNY
1400 Washington Ave.
Albany, NY 12222
Phone: (518) 442-4574
E-mail: nmetz@atmos.albany.edu

ABSTRACT

The first week of July 2003 saw twelve coherent mesoscale convective systems (MCSs) propagate across the upper Midwest. Three of these met the criteria set forth for a derecho and are of interest here. Pre-existing baroclinic zones were the focus for moisture pooling while warm advection and the associated isentropic upglide over the baroclinic zones allowed for continued moisture infusion. Steep mid-level lapse rates, along with daily diabatic heating, allowed for destabilization of high CAPE atmospheres. Shortwave disturbances (potential vorticity anomalies) helped to strengthen the upper-level flow, which aided in the generation of the derechos once organized MCSs developed. Deep layer shear in excess of 40 knots favored derecho evolution. The intensification of the nocturnal low-level jet further enabled high equivalent potential temperature/CAPE (surface based) air to accelerate poleward where it was intercepted by the eastward traveling MCSs. As a result of a combination of these factors, the upper Midwest saw extensive wind damage during this period associated with the derechos.

Complex interactions occurred on both the synoptic and mesoscale with each derecho event. This allowed each derecho to develop and evolve in a unique fashion as different dynamic and thermodynamic factors coexisted. In addition, other features such as the Great Lakes influenced the bow echoes, leading to intensification in one case and weakening in another. However, these interactions were not limited to the derecho MCSs. The less severe MCSs also played a vital role in the development of future convection. Fortuitously, these three derechos along with the other nine MCSs occurred during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX), which made for the availability of enhanced observational datasets.

A detailed assessment of the similarities and differences between the derecho events will be presented using model forecasts, satellite imagery, radar composites, trajectory analyses and surface observations. Additionally, a synoptic and mesoscale analysis will be presented of derecho/MCS interaction on 4-5 July 2003. Supplementary observations from P-3 aircraft as well as dropsondes released during BAMEX augment the other data. These all contribute to an understanding of the synoptic and mesoscale environments present in the upper Midwest during this week, permitting the derechos and other MCSs to be examined in great detail.

Shawn Milrad*, Eyad Atallah, and John R. Gyakum
Department of Atmospheric and Oceanic Sciences, McGill University
E-mail: milrad@zephyr.meteo.mcgill.ca

ABSTRACT

Tropical cyclones pose an annual threat to land masses in the western basin of the North Atlantic. However, the potential danger presented by tropical cyclones that transition into extratropical cyclones at higher latitudes is often overlooked. Occurring mainly during the late summer and early autumn, these storms can have a significant impact on the weather of Eastern Canada, especially in terms of extreme rainfall events. From 1979-2004, thirty-two storms originally classified as tropical systems by the National Hurricane Center, affected Eastern Canada while undergoing, or after completion of extratropical transition (ET). In addition, several cases from the unprecedented 2005 hurricane season are now included in the analysis.

Using data from both the NCEP Regional Reanalysis (NARR) and NCEP Global Reanalysis, the dynamical structures of these thirty-two cases are examined utilizing a Quasi-Geostrophic (QG) perspective. Via the Sutcliffe approximation to the QG Omega equation, cases are partitioned into two groups, "intensifying" and "decaying". Composite synoptic structures are presented for both partitioned groups, using both a QG and Potential Vorticity (PV) perspective. In addition, analyses of storm-relative precipitation distributions show that storms intensifying (decaying) during or after ET often exhibit a counter-clockwise (clockwise) rotation of precipitation around the storm center. Finally, the performance of the NARR with respect to this study is evaluated, including the lack of accuracy in the precipitation analysis over Canada, and the analysis of Hurricane Juan (2003) over Nova Scotia.

Stephen O'Clair*, Christopher Sheehan, and Eric G. Hoffman
Department of Chemical, Earth, Atmospheric, and Physical Sciences
Plymouth State University
Plymouth, New Hampshire

ABSTRACT

Surface data from Concord, NH and upper air data from Gray, ME were collected for five cold seasons (Oct. - April) from October 2000 - April 2005. The surface data were used to identify cases where either snow or rain occurred within 5 hours of the radiosonde observation time. Following the methodology of Heppner (1992), critical thicknesses and other criteria were calculated and a standard deviation model for snow/rain events was developed for Concord. Results show that mean and critical thicknesses for snow events at Concord were similar to those reported by Heppner (1992) for Albany, NY. In addition the parameter that best distinguishes rain and snow events in Concord was investigated. The 1000-700mb +1SD snow model parameter of 2812m was the best predictor. Theoretically 84% of all snow cases in Concord occur with a 1000/700mb thickness at or below 2812m. Yet, only 3% of rain cases we studied occurred with a 1000/700mb thickness lower than this value. Finally, two short case studies were completed: one with abnormally cold thickness values during a rain case and the other with abnormally warm thickness values during a snow case. Results showed that the cold rain event took place with a steep temperature lapse rate, and surface temperatures just above freezing. The warm snow event was marked by a stably stratified sounding with temperatures generally close to freezing up to 700mb.

John S. Quinlan
NOAA/National Weather Service
Albany, NY
E-mail: john.quinlan@noaa.gov

ABSTRACT

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.

Dr. Jason Shafer
Lyndon State College
Lyndonville, VT
Email: jason.shafer@lyndonstate.edu

ABSTRACT

This talk will highlight recent research on strong cold fronts over the western United States. Results from this work show that strong cold fronts exhibit an interesting geographic frequency, with a maximum downstream of the Rocky Mountains and minimum at or near the Pacific coast. Strong cold fronts are also more frequent seasonally from late spring to early summer and diurnally from the late afternoon and early evening. A secondary maxima of events occurs over the Intermountain West, implying that cold fronts likely develop and intensify downstream of the Sierra Nevada and Cascade Mountains. Closer inspection as to how strong cold fronts develop over the Intermountain West suggests that a combination of synoptic and diabatic process are responsible for their rapid intensification.

Alan F. Srock*, Lance F. Bosart, and John Molinari
Department of Earth and Atmospheric Sciences
University at Albany/SUNY
1400 Washington Ave, Albany, NY 12222
Phone: (518) 442-4574
Fax: (518) 442-4494
Email: srock@atmos.albany.edu
bosart@atmos.albany.edu
molinari@atmos.albany.edu

ABSTRACT

Landfalling and near-land tropical cyclones (TCs) provide a challenging forecast problem, especially regarding major threats like storm surge, high winds, and heavy rainfall. Although the dangers from strong winds and storm surge generally weaken rapidly with increasing distance from the core of the circulation, the precipitation structure associated with a landfalling TC does not fit any specific model, and is far more likely to have maxima far removed from the center of circulation. 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. Normally considered as cold-season phenomena, coastal fronts and cold-air damming can be induced by a nearby tropical cyclone in the right position with respect to the coastline.

Atlantic Tropical Storm Marco (1990) was chosen for this 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.s track and its associated wind field were a primary cause of the heavy precipitation and flooding recorded during this period. Synoptic upper air analyses from NCEP/NCAR's North American Regional Reanalysis (NARR), NHC Best Track data, and hourly high-resolution surface data from the USAF's DATSAV3, NCEP's ADP, and ICOADS will be used to explain how the coast's physical features combine with the TC to induce the mesoscale features and thus modify the total precipitation distribution.

Scott Steiger
SUNY/OSWEGO
Oswego, NY

ABSTRACT

Total lightning mapping, along with radar and National Lightning Detection Network (NLDN) cloud-to-ground lightning data, can be used to diagnose the severity of a thunderstorm. Analysis of the 13 October 2001 supercell event (Dallas-Fort Worth, Texas), some supercells of which were tornadic, shows that Lightning Detection and Ranging (LDAR II) lightning source heights (quartile, median, and 95th percentile heights) increased as the storms intensified. Most of the total (cloud-to-ground and intracloud) lightning occurred where reflectivity cores extended upwards and were within regions of reflectivity gradient rather than in reflectivity cores. A total lightning hole was associated with an intense, non-tornadic supercell on 6 April 2003. This feature was nonexistent from all supercells analyzed during the 13 October case.

During tornadogenesis, the radar and LDAR II data indicated updraft weakening. The height of the 30 dBZ radar top began to descend approximately 10 minutes (2 volume scans) before tornado touchdown in one storm. Total lightning and CG flash rates decreased by up to a factor of 5 to a minimum during an F2 tornado touchdown associated with this storm. LDAR II source heights all showed descent by 2-4 km during a 25 minute period prior to and during this tornado touchdown. This drastic trend of decreasing source heights was observed in two tornadic storms prior to and during tornado touchdown, but did not occur in non-tornadic supercells, suggesting that these parameters can be useful to forecasters. These observations agree with tornadogenesis theory that as an updraft weakens, the mesocyclone can divide (into an updraft and downdraft) and become tornadic.

Keith Wagner*, Lance F. Bosart, and Daniel Keyser
Department of Earth and Atmospheric Sciences
University at Albany/SUNY
1400 Washington Ave.
Albany, NY 12222
E-mail: wagner@atmos.albany.edu

Michael S. Evans
NWS Forecast Office
32 Dawes Dr.
Johnson City, NY 13790

ABSTRACT

Moderate precipitation events contribute a significant percentage of total cool-season (1 October - 30 April) precipitation in the Northeast. It is important to investigate the structure and causes of these events because 1) they are relatively common, 2) they tend to occur in relatively weak synoptic-scale forcing regimes, and 3) they can be challenging to forecast. This presentation summarizes a 10-year climatology of cool-season moderate precipitation events across the Northeast and documents several case studies focusing on the synoptic-scale and mesoscale forcing that governs when and where these events occur.

A moderate precipitation event was defined as having a liquid equivalent of 0.6 - 1.3 cm (+ or -1 cm) or a snow total of 6.4 - 19.0 cm. Daily precipitation amounts were obtained from NOAA.s Local Climatological Data available through NCDC from 1994 through 2004 for 35 first-order NWS stations across the Northeast. The station domain was bounded on the west by Detroit, MI, and on the south by Charleston, WV. For each station, every day between 1 October and 30 April was examined to see if a moderate precipitation event occurred. Hourly precipitation data were used to refine the event selection process in potentially ambiguous cases such as back-to-back days where moderate precipitation occurred, but the event total was above the moderate criterion. Based on the hourly rainfall data, if there was less than a 6-h gap in the precipitation, it was considered to come from one event. Histograms were produced from these data to show the distribution of cool-season moderate precipitation events across the Northeast by city, state, and geographic region.

The results from the histogram analysis indicate that more cool-season moderate precipitation events occurred in the Great Lakes and northern New England, with fewer events farther south and east. Another peak in moderate events occurred in elevated terrain. Erie, PA, received the most cool-season moderate precipitation events over the past 10 years (197), while Baltimore, MD, received the least (95).

To help illustrate the importance of weak synoptic-scale forcing on the evolution and structure of moderate precipitation events, the results from several brief case studies will be presented. Cross sections of heavy events usually show a deep layer of weakly negative saturation equivalent potential vorticity (EPV*) in conjunction with strong midlevel frontogenesis. It was found that moderate events have a similar structure to heavy events, except that the regions of negative EPV* and frontogenesis are not as strong, deep, upright, or well aligned. The features in moderate events also tend to be more transient, thus reducing the event precipitation amount.

Christopher Thuman
SUNY Oswego

ABSTRACT

The effects of the urban heat island have been carefully studied and documented from the early 20th century to the present. However, to this date there have been few projects performed to determine the extent of urban heat islands in the northeastern region of the United States. Even less research has been conducted examining heat islands in small cities having a population less than 15,000 people. This study examines the extent of an urban heat island in Syracuse, New York (433.0was capable of producing a heat island peak magnitude of 5.2results are somewhat surprising and not expected for cities the size of Syracuse and Fulton. By examining observations from the KSYR and KFZY ASOS reporting stations located near Syracuse and Fulton respectively, it was able to be determined on a preliminary basis that surface observations of temperature at Syracuse Hancock International Airport and the Oswego County Airport near Fulton are representative of rural temperatures and do not appear to display the effects of the urban phenomenon.

Alicia C. Wasula
University at Albany/SUNY
Email: alicia@atmos.albany.edu

ABSTRACT

A composite analysis of cool season (November through March) tornado episodes across the southeast United States (US) is presented. Composites of cool season tornado episodes were created using NCEP/NCAR reanalysis data in order to examine the large-scale features which are common to tornado episodes in this region. Composites were created based upon start-time of each episode in order to identify differences between daytime and nighttime tornado episodes. Historical pilot balloon data, as well as surface data, was used to create composites of the low-level wind profile both in the climatology and in proximity to tornado episodes. Results of this study suggest that slightly stronger dynamics exist for nocturnal tornado episodes across that southeast US than for daytime episodes, and that the climatological tendency for the low-level speed and directional shear to increase along the Gulf coast at night may help contribute to the existence of the secondary peak in tornado occurrence along the Gulf coast at night.

A case study of a recent tornado episode (23-24 November 2004) across the Gulf coast will be presented in the context of this composite study. The large-scale setup of this event will be compared to the composite large-scale environment of cool season tornadoes in the southeast US. Further, a detailed examination of surface and radiosonde data will be conducted to look for evidence of parameters which may have enhanced the development of tornadoes in close proximity to the coastline during the overnight and early-morning hours (e.g., backing of the surface winds along the Gulf of Mexico coastline and/or preferential increase of the nocturnal low-level jet along the coast).

Thomas A. Wasula* and Kenneth D. LaPenta
NOAA/National Weather Service, Albany, New York
251 Fuller Road
Suite B-300
Albany, NY 12203
Email: tom.wasula@noaa.gov

ABSTRACT

Severe thunderstorms across the Northeast, are very uncommon in the late Fall and Winter. For example, Albany only averages about 3 thunderstorm days every decade in the month of November. Severe thunderstorms producing damaging winds in excess of 50 knots (58 mph) and large hail (greater than 1.9 cm) occurred Thanksgiving morning over much of eastern New York and Western New England. An anomalously strong low pressure system and its associated cold front focused an area of thunderstorms that developed between 1000 UTC and 1200 UTC 25 November 2004 from central New York southward into Pennsylvania and Maryland. There were nearly two dozen wind damage reports over New York and New England from this severe weather event.

Most of eastern New York and western New England broke into the warm sector of this complex weather system after 1000 UTC 25 November 2005. A strong 500 hPa jet streak of nearly 100 knots moved northeastward from the Delmarva region on the east side of a developing negatively tilted high amplitude trough extending from Hudson Bay south to the Tennessee Valley. Eastern New York and New England were located on the left front quadrant of the mid and upper level jet streaks with moderate divergence at 300 hPa. A very strong low-level baroclinic zone was pushing eastward across New York at 1200 UTC with 850 hPa temperatures around -1 near Buffalo and as high as +13 over southwest New England. Surface dewpoints were excess of 10 ahead of the cold front that morning. The 1200 UTC sounding from Albany revealed convective available potential energy values (CAPE) in the 250 - 750 J kg-1 range (Mean Layer CAPE was 637 J kg-1 and the Downdraft CAPE value was 629 J kg-1). The 0-6 km shear values over eastern New York were in excess of 60 knots. This indicated the high potential for organized severe convection including supercells. By 1200 UTC, a squall line developed west of the Hudson River Valley region in a low CAPE, high shear environment.

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 severe weather over the Northeast. Observational data used in the analyses will include surface and upper air observations, satellite imagery, and Albany (KENX) WSR-88D data. Also, high resolution initialized NAM model data will be shown in the presentation.

Andrew M. Way*, John R. Gyakum*, and Bob Kochtubajda
*-Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, QC, Canada
Meteorological Service of Canada, Prarie and Northern Region, Edmonton, AB, Canada

ABSTRACT

Extreme lightning events are an important component of the climate of the Mackenzie River Basin (MRB) of northwest Canada. Convective rainfall from many of these events contributes significantly to annual runoff into the Arctic Ocean, and the multitude of cloud-to-ground lightning flashes may induce many wildfires in the MRB. An identification of the dynamic and thermodynamic structures associated with extreme lightning events in the MRB is made in this study. Data from the lightning detection network operating in the Northwest Territories and gridded data from the National Centers for Environmental Prediction global and North American regional reanalyses are used.

A composite analysis of 38 extreme lightning events has shown that these events in the MRB are generally characterized by an anomalously-strong, quasi-stationary ridge in the middle and upper troposphere that dominates the basin until event onset. The presence of this ridge may increase evaporation from the surface, leading to an accumulation of water vapor in the atmosphere. The triggering mechanism of the majority of these events is cyclogenesis in lee of the Rocky and Mackenzie Mountains. In general, it has been found that for extreme lightning events, thermodynamic conditioning plays a crucial role in the amplification of dynamical impacts.

Andrew M. Way*, Thomas Milewski, and John R. Gyakum
Department of Atmospheric and Oceanic Sciences,
McGill University, Montreal, QC, Canada

ABSTRACT

Here we document fieldwork carried out in late August and early September of 2005 on Lionel Island, Great Bear Lake, Northwest Territories. The fieldwork involved obtaining atmospheric soundings via the launch of 46 weather balloons over a two-week span, for the purpose of observing the influence of Great Bear Lake, the fourth largest lake in North America, on atmospheric boundary layer structure. A documentation of the various types of atmospheric profiles, and more specifically planetary boundary layer structures, in the context of varying surface flux regimes will be provided. An assessment of the drastically different thermal structures of Great Bear Lake between the summers of 2004 and 2005 will also be made, and will be related to effects on observed weather on Lionel Island. Additionally, we will present a unique perspective of fieldwork in a remote, sub-arctic climate with a multitude of photographs, and discuss the positive and negative aspects of such fieldwork.