Extended Abstract (360K)11B.5
A Severe Weather Climatology for the NWS WFO New Orleans-Baton Rouge County Warning Area (CWA)
Suzanne Van Cooten, NDBC, Stennis Space Center, MS
The NWS WFO New Orleans-Baton Rouge county warning area presents many unique challenges for forecasters who are responsible for the issuance of hazardous weather watches and warnings. This county warning area is comprised of 22 southeast Louisiana parishes and 8 southern Mississippi counties and also includes marine watch and warning responsibilities for Lakes Pontchartrain and Maurepas and the adjacent southeast Louisiana and Mississippi coastal waters. The county warning area also experiences a large change in elevation from the tidal plains of southeast Louisiana to the higher terrain of southwestern Mississippi which rises to 400 feet above sea level near McComb, Mississippi.
A severe weather climatology was completed for this diverse county warning area of southeast Louisiana and southern Mississippi to provide forecasters a reference source for the historical frequencies and patterns of extreme weather events. For this study, the Storm Prediction Center (SPC) database, the National Climatic Data Center (NCDC) Severe Events database, and Storm Data publications were used to compile hail reports of 0.75 inches or greater in diameter, thunderstorm winds in excess of 50 knots (58 miles per hour), and tornadoes since 1950. By gathering reports from each of these databases and synthesizing the reports in QuattroPro spreadsheets, differences were found between the three databases in their listings of severe weather events. To complete this climatology, the decision was made to include an event report if one source listed the report and upon investigation it looked reasonable with other surrounding reports. With the database established, these hail, wind, and tornado events were classified on an hourly, monthly, and annual basis and also by the county/parish in which they occurred. This climatology also provides a summary of tropical systems which have affected the area to determine those weather events which were directly attributed to tropical systems. A detailed listing of hail, wind, and tornado occurrences for each of the 22 southeast Louisiana parishes and 8 southern Mississippi counties is provided on an hourly, monthly, and annual basis for the period from 1950 to November 2001. Census data was also gathered to explore population trends of severe weather reporting including mapping of county/parish population and number of county/parish storm reports for each ten year increment since 1960 to more accurately depict changes in reporting trends. In addition to exploring population biases in storm reporting, three distinct climatological studies were completed for the period from 1988 to 1995 based exclusively on SPC, NCDC, or Storm Data information to provide forecasters an understanding of the implications of using one database exclusively to compile listings of severe weather events for the county warning area.
Session 11B, Climatological Studies of Severe Storms
Wednesday, 14 August 2002, 4:30 PM-6:00 PM
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