Mid-South May Day 2010 Storms and Flooding

The second weekend in a row of significant weather had the southeast U.S., including the Mid-South, in it’s crosshairs for the first weekend in May. Here, we focus on effects of the storms in the immediate Memphis metro area, with some additional overview information regarding west Tennessee, eastern Arkansas, and north Mississippi. Many other readily available sources, including mass media, have excellent coverage of middle Tennessee. There are several links to other pages contained herein. You may wish to right-click on these links and open them in new windows/tabs in order to keep this post open.

As early as last Tuesday, MWN was raising the red flag about the possibility of severe storms and very wet conditions for Memphis in May’s Beale Street Music Festival weekend. Updates were provided on Wednesday by the NWS and MWN on this blog warning of severe weather, including the possibility of tornadoes and flooding. By the end of the week, the Storm Prediction Center had placed the Mid-South in a rare (but for the second weekend in a row) “High Risk” of severe weather for Friday night through Saturday night. The stage was set (not the ones in Tom Lee Park for MusicFest) for a potential outbreak of violent storms and a significant risk for flooding due to the expected slow motion of the approaching storm system.

As meteorologists, we never know just how these events will play out, but we typically know the potential given the atmospheric conditions. In this case, the tornado potential was high and those conditions were born out (though not as severely as the previous weekend) and the flooding potential was life-threatening, which was stressed in Flash Flood Watches prior to the event and warned of the possibility of 10-12″ in localized areas. Little did we know that the 10-12″ would be widespread across a large region (along and north of I-40 from Memphis to east of Nashville as seen in the graphic below), with isolated amounts near 16-18″ in eastern Tipton County and middle Tennessee!

The severe weather began in east Arkansas late Friday evening, triggered by an upper-level disturbance and approaching frontal system, as mainly hail and high winds and continued throughout most of the night as a line of storms moved across west Tennessee just north of the Memphis area. Meanwhile, storms remained just west of Memphis into the wee hours Saturday morning as well. A screenshot taken from StormView Mobile Radar just before 1am shows the line going by to the north of the city (below).

Along the southern end of the line, little southward progress was made and storms with torrential rain trained one after another over the same areas as the severe weather threat shifted to flash flooding. The high rainfall rates (2-3″+ per hour for multiple hours in some cases) and continuous storms brought flooding conditions to areas along and north of I-40, including Millington, Arlington, Covington, Brownsville, and Jackson/Humboldt. The image below was taken at 7:34am Saturday morning and clearly shows the delineation of very heavy rain over these areas. Many locations, including the WXLIVE! sensor in northern Bartlett recorded 8-10″ of rain in a period of 3-5 hours, while areas south of I-40, including south Memphis, Germantown, Collierville, and DeSoto County got less than 1″ of rain in the same period.

On Saturday morning, the storms finally started pushing east as run-off filled ditches and culverts, then creeks and rivers, causing flood waters to continue to rise across the region. The heavy rain threat shifted south through the metro area, though a band of very heavy rain continued to affect areas near Highway 14 (Austin Peay Hwy) through mid-morning, exacerbating flooding conditions (see the link to pictures at the end of this post). Some storms became severe as they moved east through northern Mississippi, bringing hail and high wind.

By Saturday evening, a surface low pressure and upper-level disturbance were moving from southwest AR to the northeast into southeastern MO, along the stalled front. High instability, abundant moisture, strong low and mid-level wind shear, and powerful dynamics came together to form supercell thunderstorms across the state of Arkansas during the evening hours. Evidence of the very favorable environment is depicted in the image below taken around 4:20pm, which shows storm chasers from across the nation setting up in Arkansas for the expected outbreak (each icon represents the position of a GPS-enabled chaser). Many of the storms during the evening received tornado warnings (as many as 6-8 at a time across the state of AR) as they moved towards the NWS-Memphis warning area. In all, ten tornado touchdowns were recorded across central portions of Arkansas.

One of these storms, a strong supercell producing funnel clouds, large hail, and continuous lightning, moved up the Mississippi River around 10:30pm, prompting tornado warnings for Shelby County and a premature closing and evacuation of the Beale Street Music Festival. An EF-1 tornado that was on the ground for about 1/2 mile was confirmed by the NWS in the Millington area from this storm. Supercell storms continued moving across the region through the night (mainly east of the metro area), producing additional tornadoes, including an EF-2 near Humboldt, TN, a violent 27-mile, 1/2-mile-wide EF-3 that took three lives in Ashland, MS and Pocahontas, TN, and an additional EF-2 that took another life in Abbeville, MS (complete tornado survey recap linked below). Once again, persistent storms presented additional flash flooding concerns across northeastern MS and the TN River Valley.

The stats are still being analyzed, but it appears that the areas north of Memphis that got 10″+ of rain experienced a 100-year flood, and the Nashville metro area was in the range of a 500-1000 year flood! River flooding was widespread and lasted throughout the weekend and into early this week in many cases. Unfortunately, flash flooding took the lives of at least three additional individuals in the immediate region, including one in Shelby County. Over two dozen died as a result of flooding in TN, MS, and KY combined. As for tornadic storms, there were 13 tornado touchdowns (as of this writing) in the NWS-Memphis County Warning Area (CWA) – defined as west TN, eastern AR, the MO Bootheel, and north MS. Four of these tornadoes were EF-2 or EF-3 and five deaths were attributed to tornadoes.

We at MemphisWeather.net greatly appreciate all of the positive feedback received following our coverage of the severe weather the past two weekends. We consider the provision of hazardous weather information to the public part of our mission and are grateful that so many of you found it helpful. Our thoughts and prayers are extended to all of those whose lives were affected by the storms in one way or another and encourage all Mid-Southerners to find a way to help those in need, whether through the Red Cross or similar agency, or by just extending a hand to someone personally.

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