Date: Wed, 27 Oct 2004 07:32:15 -0600 From: Robert Rozumalski Subject: Announcement: National WES case study #17 now available Greetings All, I am pleased to announce new addition to the National Case Study Library: http://strc.comet.ucar.edu/csl National WES case study #17 Title : A Prolonged Severe Weather and Heavy Rain Event Author : Jeff Craven SIMULATION OBJECTIVES The purpose of the simulation is to: * Evaluate the potential for severe weather and heavy rainfall * Practice issuing Severe/Tornado/Flash Flood Warnings * Use GFS/ETA to forecast severe weather and QPF * Review established heavy rain forecasting techniques and Corifidi Vectors * Use satellite data to anticipate severe weather * Utilize CG lightning for analysis of severe weather potential * Study the effects of mesoscale convective cold pools on low-level boundary evolution, severe weather development, and heavy rainfall production. SIMULATION OVERVIEW This simulation may be utilized in different ways. It can stand alone as a forecast exercise for severe thunderstorms/tornadoes and/or heavy rainfall. In addition, there are many opportunities to practice difficult warning decisions with supercells during a PDS Tornado Watch/High Risk that are "under producers" with respect to strong tornadoes. EVENT SUMMARY A prolonged severe weather and heavy rain event affected the Interstate 20 corridor of Louisiana and Mississippi. Supercells producing tornadoes, large hail, and damaging wind gusts were widespread along a west-east front. Ten tornadoes including an F2 were reported. Hail up to baseball size and wind gusts up to 80 mph occurred. In some cases, damaging inflow winds were were observed near the supercells. Many rounds of thunderstorms and heavy rainfall produced a swath of 7 to 12 inch rains in an 18-hour period. This represented a 125-year rainfall event. Flash flooding and river flooding ensued, with a couple of rivers reaching all-time record crests. During its record crest, the Chunky River closed Interstate 20 between Jackson and Meridian for several hours. The Pearl River reached a top ten crest of over 35 feet at Jackson. The flash flooding alone resulted in estimated damages exceeding a quarter billion dollars, with significant additional damages from severe weather and river flooding. Case #17 is available on DVD along with a companion simulation guide from the SOO/STRC National Case Study Library: http://strc.comet.ucar.edu/csl Let me know if you have any questions. Regards, Bob -- Robert A. Rozumalski, PhD NWS National SOO Science and Training Resource Coordinator COMET/UCAR PO Box 3000 Phone: 303.497.8356 Boulder, CO 80307-3000