1. Project Objectives and Accomplishments
On March 31-April 1, the Northeast was hit by a major nor'easter which produced snowfall amounts of 30 to over 90 cm over a large area. During the early morning hours on March 31, a 1002 mb low began to intensify as it propagated off the coast of North Carolina. Between the hours of 12Z March 31, and 00Z April 1st, the low central pressure decreased 14 mb from 990 to 976 mb. Many snowfall records were set including Boston with roughly 63 cm. This amount is about equivalent to what had fallen for the entire winter season to date. Due to the heavy and wet consistency of the snow, several hundred thousand customers in New England and New York were without electricity during and after the storm. These numbers were estimated at 250,000 customers in Massachusetts, 100,000 in New York and 85,000 in Connecticut. High winds were also a significant factor as were gusts which averaged in the range of 45 - 60 kt along the coast. Work has now been completed of our analysis of this storm. Noteworthy aspects of the storm include the small rainbands that developed in New England, the significant role that the terrain played in determining the type and amount of precipitation, and the role of frontogenetical forcing.
We have isolated a two-hour period, from 15 to 17 UTC on 31 March 1997, in which the rainbands develop and produce a larger amount of precipitation than was previously forecasted. By examining Rapid Update Cycle (RUC) grid files with GEMPAK 5.4 and comparing with radar data, we have produced a comprehensive analysis determining the major components producing these larger amounts. WSR-88D data from six stations from Maine to Virginia was also used to observe these rainbands. We have isolated areas of precipitation that were influenced potentially by conditional symmetric instability (CSI) and those by frontogenesis. We created hourly schematics showing the calculated values of the frontogenetical forcing and CSI and their positions in relation to the storm. It is suggested that the convective lifting mechanism dominates early in the storm, but by 17 UTC has been replaced by slantwise convection over western Connecticut and into New York. We overlaid these patterns over the base reflectivity to show their individual influence and effect on the precipitation amounts.
Around 20 UTC on 31 March 1997, the low-pressure system was just over southern New York. The 700 mb winds were moving southerly to more southeasterly in the next three hours, advecting the warm moist air from the Atlantic Ocean. At this time, the radar indicated convection was present over southern New England. This area is congruent with a region of total frontogenesis of 4° C/100km/day or larger. An area of potential CSI was located throughout southern New England and southeastern New York. This area included the convection and the stronger frontogenesis regions. However, the banded precipitation found in this vicinity could only be seen outside and to the northwest the areas of radar indicated convection and strong frontogenetical forcing. This is consistent with the 700 mb southeasterly flow at this time period. As the storm moved up the Atlantic coast into the Long Island, NY, around 21 UTC frontogenesis became the dominant forcing mechanism associated with the area precipitation. A close analysis of the horizontal and tilting term of the two-dimensional total frontogenesis shows the dominance of the tilting term in ending the precipitation in eastern New England.
Finally, the development of a suite of "procedures" to be used with the NWS Advanced Weather Interactive Processing System (AWIPS) continues. These "procedures" will allow NWS forecasters the ability to efficiently investigate observed and forecast data for indications of CSI and orographic influences that may result in enhanced and excessive precipitation. This program will guide forecasters through a technique examining a potential CSI environment. The procedure would display the various fields and products used to examine the potential CSI environment.
2. Summary of University/ NWS Exchanges
A University at Albany undergraduate, Vivs Laliberte, worked with us through his National Weather Service internship. These internships usually involve forecasting experience. However, Vivs was able to gain research experience by collecting data, writing programs and helping produce topography maps. Other university students, both graduate and undergraduate, are now becoming involved in collaborative projects due to our success. One major benefit has been incorporating the research methods of the university with the equipment and forecasting ability of the weather service participants. The exchange of information and ideas has been beneficial to better recognize and appreciate various investigative techniques
3. Presentations and Publications
Honikman, S.F. and T. Janus, 1997. An Evaluation of the April Fools Snowstorm 1997 and the Role of Elevation Dependency, The 22nd Northeast Storm Conference, Saratoga, NY, March 1997.
Honikman, S.F. and J.L. Blaes, 1998. An Evaluation of Frontogenetical Forcing and the Role of Conditional Symmetric Instability (CSI) on the April Fools Snowstorm 1997, The 23rd Northeast Storm Conference, Saratoga, NY, March 1998.
Janus, T. and S.F. Honikman, 1998. An Evaluation of Frontogenetical Forcing and the Role of Conditional Symmetric Instability (CSI) on the April Fools Snowstorm 1997, NWS Forecast Office Albany, NY, Annual Spring Meeting, May 1998.
Honikman, S.F. and J.L. Blaes, 1998. An Evaluation of Frontogenetical Forcing and the Role of Conditional Symmetric Instability (CSI) on the April Fools Snowstorm 1997, NWS Forecast Office, Albany, NY, Annual Fall Meeting, October 1998.
Honikman, S.F. and J.L. Blaes, 1999. An Evaluation of Frontogenetical Forcing and the Role of Conditional Symmetric Instability (CSI) on the April Fools Snowstorm 1997, 1st annual Northeast Regional Operational Workshop, NWS, Albany, NY, September 1999.
Now that our research has concluded, work continues on writing up our results for a referred journal.
4.1 University perspective
A project like this broadens the horizons of both NWS and university participants. NWS team members have been exposed to a wealth of theoretical meteorology and experience possessed by the university team members. The university team members now have a different perspective on the value of the research results based on a forecaster's obligation to the public. Due to the success of this project, not only with the findings, but with the strong research relationship that was created between the NWS forecasters and the university participants, the university participants have now become involved in a second COMET research project with the NWS. (Advanced Forecast and Warning Criteria for Tornadoes and Severe Thunderstorm in the Northeastern United States, #320-7089A) The involvement of university and NWS members in this project represents an acknowledgment that this investigation covers a critical forecast problem facing meteorologists in the northeast.
4.2 NWS perspective
This endeavor has broadened the horizons of both NWS and university participants. NWS team members have been exposed to a wealth of theoretical meteorology and experience possessed by the university team members. The unencumbered approach to forecasting, without operational restraints or biases possessed by many university participants was refreshing to the NWS members. University members have an increased appreciation of the pressure faced by NWS meteorologists including real time data issues, deadline pressures, and operational limitations and how forecasters must deal with these issues at times. This project has brought together many people with differing strengths and expertise, combining the various skills and experiences available into one product will be the greatest benefit to the NWS. This project represents one of the first investigations incorporating the new capabilities of the Advanced Weather Interactive Processing System (AWIPS).