...Thunderstorm-Generated Heat Bursts Affect Portions Of South Central South Dakota...
Thunderstorms this morning and early this afternoon have produced a phenomenon called a heat burst. Two conditions are necessary for a heat burst - very warm and dry air around 10000 feet and relatively cool air near the surface. A heat burst occurs when the very warm and dry air at the mid-levels of a thunderstorm is accelerated downward to the surface. As the air moves lower in the atmosphere...it warms due to the compression. If the air is forced toward the surface with enough speed...it will reach the ground. Because of the warming...the air forced to the surface will be much warmer and drier. Therefore...temperatures will rise 10 or even 20 degrees Fahrenheit in 10 to 15 minutes while dew points can decrease by the same amount. In addition...since the air is accelerated to the surface...strong wind gusts accompany the temperature rise. The effect of a heat burst can last a couple of hours.
There were several examples of heat bursts today. In Winner South Dakota...the temperature rose from 74 degrees at 5 am to 90 degrees at 7 am. At the same time...the dew point went from 57 degrees to 48 degrees and the wind gusted to 62 mph at 701 am. In Huron South Dakota...the temperature went from 74 degrees at 8 am to 85 degrees at 9 am. The dew point went from 65 degrees to 56 degrees at the same time with the wind gusting to 36 mph. The storm that produced this heat burst was to the west of Huron. Finally...in Wagner South Dakota...the temperature rose to 99 degrees at 1230 pm with wind gusts to 86 mph.
Philip Schumacher
Science and Operations Officer
Sioux Falls, South Dakota
Issued as:
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE SIOUX FALLS SD 230 PM CDT MON JUL 30 2001
