9 June 2011
A rare heat burst was recorded last night in Wichita, Kansas! The temperature at midnight was 84F but an hour later, as a thunderstorm nearby died out, the temperature hit 102F! The winds gusted to over 45 mph at the same time. Needless to say it was not a night to be a lineman for the county (If you don’t get that you should really buy a Glen Campbell record)!
So what caused it?
There are some real clues as to the cause of these events in the upper air weather sounding (taken at 7 PM local time) from near Enid Oklahoma. Notice the the big layer of dry air just above the surface. The atmosphere was very unstable though, and thunderstorms were in the forecast. At around midnight a thunderstorm developed just south of Wichita, and set the stage for the heat burst.
As rain fell into the dry air layer at around 2-3 thousand meters above the surface, it evaporated rapidly. The evaporating rain cooled the air very quickly, and this cool air was now much heavier than the air around it. This heavy, rain cooled air, fell rapidly to the surface, but heated due to compression at the standard adiabatic rate of 10 C per 1000 meters. If it fell 2500 meters, then the temperature of that rain cooled air would have risen 25C!
The Wichita radar shows a thunderstorm just south of the city at midnight.