| Above: In this Tuesday, May 28, 2019 aerial photo, a home west of Celina, Ohio, has had its roof torn off by an EF-3 tornado that was part of a storm system that passed through Monday night. After Monday's tornadoes, Ohio Gov. Mike DeWine declared a state of emergency in the three counties with the most damage. Image credit: Ryan Snyder/Daily Standard via AP. |
Another intense bout of severe weather assaulted a large swath of the Midwest and Mid-Atlantic U.S. on Wednesday--the thirteenth consecutive day of what has been an incredibly persistent and prolific severe weather outbreak. NOAA’s Storm Prediction Center (SPC) logged 24 preliminary reports of tornadoes across four states on Wednesday, along with 45 reports of large hail and 210 reports of high winds. That brings the total number of reported (not confirmed) tornadoes since May 17 to 402, and the total number of tornado, large hail, and high wind reports to 2779--an astonishly high number of severe weather events for a two-week time span. Severe weather killed at least two people on Wednesday--one from a falling tree in West Virginia, and one from strong thunderstorm winds in Kentucky.
Heavy rains of 1 – 4” fell in eastern Oklahoma and western Arkansas on Wednesday, aggravating damaging flooding that is occurring on the Arkansas River. All-time record flood crests are occurring or are predicted in the coming days along a 150-mile stretch of the river in eastern Oklahoma and western Arkansas, as detailed at weather.com.
Update: As of 10 PM ET, at least 236 tornadoes now confirmed since May 16. Approaching 300 for the entire month of May -- which actually isn't far off from what a "normal" May used to be in terms of touchdowns. Just quieter in recent years. (1990-2018 Avg: 264 / Median: 240) pic.twitter.com/zVO31mv1Rb
— Steve Bowen (@SteveBowenWx) May 30, 2019
A welcome change in the large-scale weather pattern is at hand
The prolonged stretch of severe weather this May has been caused by an unusually cold and persistent upper low in the western U.S. combined with a strong ridge of high pressure that brought record May heat over the Southeast U.S. A powerful jet stream ran south of the upper low and north of the high, bringing energy and spin to the thunderstorms that formed each day, thereby creating spinning supercell thunderstorms that spawned tornadoes. This pattern is weakening and shifting, which will allow the Southeast U.S. to cool, the Western U.S. to warm, and the Midwest U.S. to experience dryer and less stormy weather.
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| Figure 1. The severe weather outlook for Thursday, May 30, from NOAA’s Storm Prediction Center (SPC). SPC has not outlined any “enhanced” or greater risk areas, though a “slight risk” of severe thunderstorms capable of damaging wind gusts, hail and a couple of tornadoes is expected for a portion of the Ohio Valley to the Mid-Atlantic. There is also a slight risk of severe thunderstorms from eastern New Mexico/the southern High Plains into central and southwest Texas. |
On Thursday, for the first time since May 16, SPC has not outlined any “enhanced” or greater risk areas for severe weather, though a “slight risk” of severe thunderstorms was predicted for a portion of the Ohio Valley to the Mid-Atlantic, and from eastern New Mexico/the southern High Plains into central and southwest Texas. SPC’s severe weather forecast for Friday and Saturday ratchets the risk down another notch, with just a “marginal” threat of severe weather over potions of the Midwest and East Coast. Even the center's Day 4-8 outlook (Sunday-Wednesday) is devoid of any threat areas, although they note a few severe thunderstorms may pop up on the central High Plains—very typical for early June.
The diminishing severe weather threat also brings with it a diminishing chance for flooding rains. On Thursday, for the first time since early May, NOAA did not predict any large-scale seven-day rainfall amounts in excess of four inches for the U.S.
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| Figure 2. Seven-day precipitation amounts for the period ending Thursday, June 6, 2019. For the first time since early May, no seven-day large-scale rainfall amounts in excess of four inches (orange colors) are predicted for the U.S. Image credit: NOAA/NWS. |
In the Southeast U.S., at least nine cities have tied or set all-time May monthly high-temperature records over the past week, including 101 degrees in Augusta, Georgia, and 100 degrees in Charleston, South Carolina. A cold front will push through the region Friday, bringing cooler temperatures and an end to the record heat.
In the Western U.S, May has been cool and wet. Temperatures in Las Vegas and Phoenix have been more than 6 degrees cooler than average, and Tucson, Arizona, has yet to reach 100 degrees this year, which typically occurs by mid-May. Through May 27, it had been the wettest May on record in Sacramento, CA, Fresno, CA, and Flagstaff, AZ. By this weekend, temperatures will be close to average over much of the Western U.S., thanks to the coming pattern change.
Bob Henson contributed to this post.
