Mayor and NWS in Hissy Fight

Over supposedly "blown" (Mayor), or "impossible" (NWS) forecast. We report, you decide! - HLG

Rare condition caused flood
By Kelly House • khouse@courier-journal.com • August 4, 2009


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 minicold front that collided with clashing wind streams from the northwest and south, trapping the storm over downtown Louisville, area meteorologists said.

“No one expected the thunderstorm to set up the way it did,” said Mike Callahan, a hydrologist with the National Weather Service in Louisville.

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,” Callahan said.

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, WHAS-11 meteorologist Monty Webb said.

That cool air, combined with colliding wind streams, clogged weather patterns to stop the storm over Louisville.

During a press conference to assess the storm's damage, Mayor Jerry Abramson and Metropolitan Sewer District Director Bud Schardein blamed weather experts for failing to give advance warning of the storm, saying it made preparing for the emergency difficult.

But Callahan said meteorologists couldn't possibly have seen the pattern coming.

“Nobody can predict storms like this without any type of advance warning,” Callahan said. “The technology and the science just doesn't allow it. The only thing we can do is record when the pattern sets up and send out the warnings, and we did that.”

Meteorologists issued their first severe thunderstorm warning for south-central Indiana at 6:38 a.m. The warning was extended to the Louisville metro area at 7:50 a.m., and the first showers began about half an hour later.

Flash-flood warnings for the metro area followed between 8:15 a.m. and 9:15 a.m. By 9:40 a.m., Louisville entered emergency flood stage, as reports poured in of trapped vehicles, floating debris and flooded streets and buildings.

Most of the rain had subsided by 10:30 a.m., leaving behind flooding throughout south-central Indiana and the metro area as far south as northeastern Bullitt County.

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.

A second storm front Tuesday afternoon dropped just a few tenths of an inch of rain. But it was enough to aggravate flooding throughout the Louisville area.