Thursday, September 11, 2014

Recap of the September 11th Flood of 2014

While most readers of this blog have clear memories of 9/11/2001, many of you will now remember 9/11/2014 for some time to come as well. The flooding that took place today may be as bad as some of you have witnessed, or at least rank in the top couple of events that you have personally experienced.

It began innocently enough last night with a forecast of showers and thunderstorms in the early morning hours that would likely impact rush hour. But the bigger story was clearly going to be the arrival of autumn air and promise of a pleasant weekend that many have been looking forward to after a late-arriving summer. Or so we thought...

As storms well to our north moved towards the region overnight, an outflow boundary moved slowly into the metro from north to south. Behind it, storms rapidly fired on a southerly low level jet stream and plenty of warm, moist air. The storms moved east, but continued to fire behind the outflow, resulting in a "training" effect. Storms fired near the Mississippi River repeatedly and moved east across Tipton, then Shelby and Fayette, and finally DeSoto Counties.

The hardest hit area during a couple hour period during rush hour was a stretch from Frayser to Raleigh to Bartlett. Later, during the mid-morning hours, DeSoto County, particularly the center of the county near I-55, saw repeated storms. Rainfall totals of 6-10" were found in these corridors, though widespread 2-5" readings were found throughout the metro.

48 hour precip totals for the event with most of the rain falling the morning of the 11th. Click for larger image.

Below you'll find a video loop of the NWS Doppler Radar from 4am until noon. Feel free to play it a couple of times and watch the storms fire behind a southbound "front" (outflow boundary) and train over the same areas.

Next, we've produced a Storify that describes the events using social media posts and images, many of which are ours. It summarizes the events quite well I think. (It's long. Just click "Read Next Page" a couple of times as you read down the page. At the end, you'll return to the closing paragraph from this blog.)

As mentioned in the Storify, the rainfall total of 7.23" in just 3 1/2 hours at MWN headquarters in Bartlett is considered a 1,000 year rain event. It's not the same magnitude everywhere in the metro, but given the amount of rain in the duration of time that it fell, you'd be hard pressed to see another event like this in your lifetime. (For comparison, former Olive Branch mayor and meteorologist Sam Rikard's rainfall in Olive Branch was about a 400 year event.)

Hopefully you have a story of your own to tell without having been harmed in some way by the power of Mother Nature. I think I'll remember this one for a LONG time to come!

Erik Proseus, MWN Meteorologist

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