Extended Abstract (1.6M)6.4
The warning time for cloud-to-ground lightning in isolated, ordinary thunderstorms over Houston, Texas
Nathan C. Clements, Texas A&M Univ., College Station, TX; and R. E. Orville
Lightning detection over Houston, Texas is possible with the Lightning Detection and Ranging (LDAR-II) network and the National Lightning Detection Network (NLDN). A comparison of the two datasets in conjunction with 37 isolated, ordinary thunderstorms reveals a time separation of 3.1 minutes between the first detected Very High Frequency (VHF) source (i.e. first intracloud discharge) and the first cloud-to-ground (CG) lightning flash. This CG warning time is increased to 16.1 minutes when using the radar-defined criterion of the 30-dBZ contour at the -10°C isotherm level.
Several attempts were made to establish a similar characteristic that could be used to forewarn the occurrence of the final CG in this storm type. Based on the average radar characteristics during the last CG flash in each thunderstorm case, CG activity comes to an end when the 45-dBZ echo falls below the -10°C isotherm.
Detection efficiencies that remain slightly less than perfect for each network may have allowed for some error when analyzing VHF sources and ground flashes for each convective case. Exhibiting this possible error were Cases 8, 9, 10, and 29. They actually recorded a greater number of CG flashes than intracloud flashes, which is contrary to typical lightning characteristics (MacGorman and Rust 1998, p. 190).
Future studies hope to increase the number of thunderstorm cases to analyze as the LDAR network continues to observe more lightning events. Also, similar approaches could be implemented in differing geographic regions of the country to observe if these lightning characteristics vary depending on latitude, longitude, or climate.
Supplementary URL: http://www.met.tamu.edu/ciams/ldar/index.html
Session 6, Lightning Prediction Using Observations and Models
Wednesday, 23 January 2008, 10:30 AM-12:00 PM, 222
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