...FLASH FLOOD WARNING PARTS OF BHM METRO...
Scattered thunderstorms have returned to central Alabama this afternoon. What I found interesting was the concentration of storms over the BHM metro area. Often on a sunny day, the city gets a little bit hotter than surrounding rural areas due to several factors, including 1) concrete holds more heat than grass, think about a parking lot, 2) air conditioners put out heat, and 3) so do cars and other machinery. Warmer air, all else the same, makes the air more unstable, and sometimes results in thunderstorms over the city. This warm area over the city is called the "Urban Heat Island", and also occurs often on clear, calm nights in winter, possibly biasing temperature records to the warm side over the past 50 years or so. It is possible that the storms that formed over BHM today formed there due to the urban heat island. Look at temperatures at 2 pm, before most storms got going.
There was a concentration of temperatures of 91-92 over southern Jefferson and northern Shelby counties, where the storms have been. A flash flood warning is in effect due to the heavy rain, saturated ground, and full creeks, for areas like downtown Birmingham, Hoover, Vestavia, Irondale, and Cahaba Heights.
Dr. Tim Coleman