_https://www.facebook.com/NOAA.NSSL/posts/10152249561272455 said:
US National Weather Service Aberdeen South Dakota
Here's some science to share with your coworkers this morning!
We had a fairly rare event occur across several locations this morning. If we had more observation sites across the state, we likely would've recorded more. The event that occurred is called a Heat Burst!
Here are the ingredients needed for Heat Bursts to occur:
A very dry layer of air needs to exist in the lower to middle atmosphere. Now, look at the graphic. The image in the upper left of the graphic shows a sounding at Chamberlain, SD around 3AM. This just shows us how the temperature and the dewpoint change with height. Notice how the green and red lines separate as they approach the lower atmosphere. This means a very dry air layer is in place just above the ground. The second ingredient we need is a decaying or weak shower/t'storm. Notice the radar image taken at 3 AM (bottom left image). There are scattered echoes near the star which demarcates Chamberlain, SD. These had previously moved through the areas across central and eastern SD.
So what happens?
As the rain falls into the extremely dry and warm layer, it evaporates. As it evaporates, this pool of air starts accelerating toward the ground. Now, something interesting happens. Once all the moisture has evaporated out of the air, there is no more heat to release to the environment. So what happens? It begins to warm dramatically as it accelerates toward the ground. When this happens at night, like last night, the results can be pretty interesting! Here they are...
Chamberlain, SD at 1AM was 74 F with a relative humidity (RH) of 89%. At 2AM, it had warmed to 90 F with an RH of 23 %!! Winds also gusted to 46 mph during that hour. How crazy is that?
Presho warmed to 90 F at 2 AM
Danforth warmed to 87 F at 3 AM
Huron warmed to 91 at 4 AM
These all occurred as the showers shown on radar moved from west to east across the state and in most instances will turn out to be the warmest temperatures these locations reach today!