Monday, August 4, 2008

It's HOT, but Not Here

Well, so much for the big heat wave. The temperature only rose to the mid 80's today. There were a lot of clouds around, so I imagine that kept the temperatures down.

Here's something interesting. Between 415 am and 445 am CDT August 3rd, the city of Sioux Falls experienced a convective heat burst. Temperatures rose rapidly from the lower 70s to 101 degrees in a very short time. This rapid rise in temperature was also associated with wind gusts of 50 to 60 mph, as well as a rapid drop in dew points. The official high temperature will be 99 degrees as with automated weather stations, only the 5 minute mean temperature and dew point are used.

A heat burst occurs when warm air from 10,000 to 20,000 feet above the surface is forced to the ground. Typically when air comes down to the surface with thunderstorms, it is much colder than the air at the surface. However, especially during the late night and morning, very warm air can be forced to the surface if the air reaches the surface without rainfall occurring. When this happens, the temperature will rise as much as 30 degrees, and the dew point will drop by 20 to 30 degrees. Heat bursts are also accompanied by strong to damaging winds. However, unlike many cases with damaging thunderstorm winds, little to no rain will fall when the heat burst occurs. This is because if it were to rain, the air would rapidly cool and moisten due to evaporation.