The last post here was about the devastating tornadoes in St. Louis and Kentucky in the middle of the month on May 15th. I noted that it wasn’t a classic outbreak. Though there was quite a bit of severe weather, it wasn’t overwhelmed by multiple tornadic supercells. The tornadoes that occurred were devastating, but they weren’t particularly widespread.

In the 11 days, including today, since that terrible day, only one day has had little severe weather, the 21st which saw 20 severe reports (most from western Pennsylvania, where there were some small tornadoes, ironically) versus hundreds of severe reports on all of the other days. What’s more, is that there has been a predilection for storms in the south central US (Texas to Alabama, approximately). There hasn’t really been a let up.

The 17th, 18th and 19th were the busiest of those days, with several hundred reports from storms, including wind, hail and tornadoes. The 17th and 19th also featured a few injuries as the result of stronger storms. The organized severe weather has since started to focus on hail and particularly strong winds in the last few days, and has increasingly targeted the lower Mississippi Valley, as opposed to the High Plains.

This is because of an upper level gyre centered over the Great Lakes that has become disconnected from the main jet stream. Flow through the gyre is allowing for weak shortwaved redevelopment at the surface, moving from the Red River Valley to the Lower Mississippi Valley before dissipating and starting over the next day. This gyre is going to recycle about 4 more times, meaning about 4 more days of severe weather from Texas to the Carolinas. By the weekend, it will fold into the jet structure and start moving east and out of the southern US for the weekend.

The transitional season of spring has allowed this gyre to keep pumping severe weather into the region, because the Gulf keeps supplying fuel to the fire. However with the gyre having a tough time moving, the weather has strafed the same ground over and over, and has robbed it of it’s potency since the clash of air masses has been blunted, and the lines between warm and cold air were increasingly blurred. Still, it has been severe couple of weeks, even if not in the news cycle consuming fashion of a typical spring outbreak.