Flooding, Tornado Threats Continue after Torrential Rains in Central Oklahoma

The Plains erupted on Wednesday with a batch of slow-moving tornadic supercells that morphed into prodigious rainmakers. More than four dozen tornado reports had been received by NOAA’s Storm Prediction Center by early Thursday. Pockets of wind/tornado damage were reported near Bridge Creek, OK, and across parts of the south metro area of Oklahoma City/Norman (see Figure 1). Two critical injuries and 10 other injuries were reported at a mobile home park and RV park in southeast Oklahoma City. The town of Rosedale, NE, also saw several homes damaged by a tornado. The more serious threat by late evening became flash flooding, especially across the Oklahoma City area, where a strip of heavy rainfall landed very close to a prior deluge the night before. The resulting 2-day totals (see Figure 2) exceeded 8” in spots. Oklahoma City’s total of 7.10” on Wednesday (including 6.03” in just three hours) was a record for any day in May and the third-highest all-time calendar-day total. Widespread flooding was reported across south parts of the metro area, and here in Norman, where I'm based this week, this was one of the heaviest downpours I've seen in a long time. Climate Central has a great roundup of statistics related to Oklahoma City's record rainfall. CoCoRaHS 24-hour rainfall reports as of 8:00 am CDT also show a large swath of torrential rain over southeast Nebraska, with several reports of between 8" and 11". Significant flooding occurred in the Lincoln, NE, area, with reports of water rescues under way on Thursday morning.


Figure 1. A hotel in northwest Norman, OK, received substantial exterior damage on Wednesday when a tornado passed just to its north. In 1991, this hotel (a Holiday Inn at the time) played host to the Third Fujita Tornado Symposium. Image credit: Trevor Hutson, used with permission.

The stubborn upper low parked over the Southwest isn’t expected to begin moving out until the weekend, so additional rounds of severe weather are possible over the next several days. The stronger upper-level winds expected to move over the Plains on Saturday will boost the potential for a significant outbreak of tornadic storms. In addition, many already-soaked areas will remain under the gun for the potential of even more heavy rain. While tornado threats often dominate severe-weather coverage, flash flooding can be the greater hazard. More people died from drowning than from tornadoes in the tragic May 31, 2013, storm that killed famed tornado chaser Tim Samaras and 20 other people. Atmospheric moisture will remain extremely rich across the south central U.S. until the upper low moves out, so the flooding risk will have to be taken very seriously.


Figure 2. Rainfall totals across Oklahoma for the 48 hours ending at midnight Wednesday night. Image credit: Oklahoma Mesonet.

Update on 90L
A hurricane hunter aircraft is in the air investigating Invest 90L, the nearly stationary area of disturbed weather off the coast of South Carolina. There will be a blog post by early afternoon detailing their findings. 90L is still on track to potentially become a subtropical depression by Friday, and bring heavy rain and high waves to South Carolina and North Carolina over the weekend. In their 8 am EDT Thursday Tropical Weather Outlook, NHC gave the disturbance 2-day and 5-day odds of development of 70%, respectively.

Bob Henson