Las Vegas Event 8 July 1999Las Vegas Event 8 July 1999

Jennifer H. Maxwell

Las Vegas Flash FloodsLas Vegas Flash Floods

Strong thunderstorms in the Las Vegas valley occurred between 18z and 19z.

More than 2 inches of rain fell in less than 1 hour resulting in damaging flash floods (rainfall rates were likely over 4 in/hr).

Higher amounts likely over higher terrain to the NE and NW of the valley.

1145Z 08 July 1999

1145Z 08 July 1999

6-h forecast valid at 18Z ETA

1200 UTC 8 July 1999 surface analysis

Desert Rock PW=1.68”

Yuma PW= 2.01”

700 mb – green, 500 mb- red

14Z 8 July 1999

1hr radar accum 1902z

ConclusionsConclusions

Tropical connectionHigh surface dewpointsLocation of upper level high and inverted

500 mb trofOrographicsUrbanizationPossible effects from earlier convection NE

of Las Vegas?

ResultsResults

Low centroid storms Over 2 inches of rain in less than 1 hrMore rapid runoff (urban area)