Posted at 4:00 PM on August 17, 2009
by Paul Huttner
Here's one you can file under "weird weather news."
Early Friday morning around 2 am, the temperature in Pierre, South Dakota rose from 79 to nearly 90 degrees. That's right; the temperature rose about 11 degrees in an hour, in the middle of the night!
What caused this unusual rise?
It's called a heat burst. It can happen when thunderstorms die out.
Here's what likely happened in the skies over Pierre Friday.
The updrafts that have built the storms are gone. The air and water that has been lifted high into the atmosphere now begins to descend toward the ground. At first there may be some evaporational cooling of the air mass. This makes the air heavier and it descends more rapidly.
As the air dries and speeds up, it begins to warm as it descends. Descending air can warm at 5 to 10 degrees per thousand feet of descent depending on conditions. This is similar to a Chinook Wind effect in the lee of the Rockies.
As the downdraft hit the ground in Pierre, the winds kicked up and temperatures shot up to 90 degrees at 2 in the morning!
Heat bursts are almost impossible to detect and forecast. There is really no good way to measure what's coming at you from 10,000 feet straight above you in the middle of the night.
It's amazing how many cool weather phenomena nature can send our way. It certainly keeps my life interesting!
It certainly is fascinating. I'm wondering what websites you would recommend for someone first approaching meteorology. Other than this site, of course!