Sunday, August 25, 2013

Southwest Storms

Today's most intense thunderstorms occurred primarily (but not exclusively) over southern Nevada and California where there was a combination of moisture, instability, and strong surface heating.  Although it rained further east, and some strong storms were observed, the widespread cloud cover appeared to limit convective intensity.

Many of the cells in southern Nevada and California were slow moving, resulting in some significant accumulations in some areas.  The products issued today by the National Weather Service Las Vegas Forecast office includes a long list of flash flood warnings, severe thunderstorm warnings, storm reports, etc.  I never know whether or not to trust the radar-derived precipitation totals, but there are some big numbers reaching several inches in a few locations below.  

Source: NWS
The Clark County Regional Flood Control District has a nice web site that provides access to gauge-based precipitation observations and radar overlays.  Sites near the heavy precipitation accumulation area northwest of Vegas show accumulations of as high as 4.06 inches.  
Clark County Regional Flood Control District
That is an impressive storm and, if I am interpreting the tabular data available on the Clark County Regional Flood Control District web site correctly, it has a recurrence interval greater than 100 years (for any given location).  A four inch accumulation is also very close to the average annual rainfall in the area.

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