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COMET_CASE_025 project description

COMET Case Study 025:Salt Lake City Tornado/Long Island Floo


Case 025 represents one of the most devastating weather events in Utah's history. On August 11th 1999 a tornado moved through downtown Salt Lake City between 18:45 and 18:55 UTC. The tornado damage was rated as F2 on the Fujita scale, and was resonsible for the first recorded tornado death in the state's history and dozens of injuries. Hail up to 1.5 inches in diameter was also reported from this storm. In addition, on the East Coast, flash floods impacted Long Island. Between 13Z and 17Z on August 11, clusters of thunderstorms formed along a warm front. As they moved very slowly east, they produced heavy rain that caused flash flooding from Deer Park to Manorville, NY. Rainfall rates estimated at 1 to 2 inches per hour for up to 3 hours generated rainfall totals from 3 to 5 inches. Water, rapidly accumulating in low-lying areas, swept cars away and trapped people in their vehicles.


The case allows the study of severe weather in mountain regions, and also the study of convective flash flooding on the East Coast.

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Temporal coverage

Begin date: 1999-08-11 00:00:00, End date: 1999-08-12 23:59:59

Spatial coverage

Minimum latitude: 25.000000, Minimum longitude: -125.500000
Maximum latitude: 48.800000, Maximum longitude: -66.900000