They knew it was going to rain, but National Weather Service meteorologists say they couldn't have predicted the EXTREMELY RARE circumstances that stalled a massive storm front over Louisville Tuesday, flooding the area with RECORD RAINFALL.
A run-of-the-mill thunderstorm created a mini-cold front that collided with clashing wind streams from the northwest and south, trapping the storm over downtown Louisville. “No one expected the thunderstorm to set up the way it did." Trapped storms usually dump their water and weaken after about 30 minutes. But on Tuesday, warm, damp air from the south flowed above the cold front to feed the storm for hours. “It just kept rebuilding itself right on top of Louisville."
Known as an outflow boundary or downburst, the phenomenon generates cool air that drops from the cloud at high speed, then spreads along the ground. That cool air, combined with colliding wind streams, clogged weather patterns to stop the storm over Louisville. By the time the storm passed, more than 6 inches of rain had dropped in some areas - creating THE WETTEST AUGUST DAY ON RECORD. The storm nearly doubled the average August rainfall of 3.4 inches.