Good afternoon! Wanted to touch on where we stand with severe weather and tornadoes this year compared to normal. It’s no secret this has been an unusually quiet year regarding tornadoes, particularly this past spring. It seems like its been an extreme year of weather, right? But why the lack of tornado activity compared to normal? I’ll explain the reason behind this in the blog. First off, wanted to show you show you some of the preliminary tornado counts for the year thus far. Looking at the U.S. as a whole, here are the tornado counts so far this year vs. what we normally see.
Check out the tornado counts for each year from 2005-2018 below. 2018 is the black line. For a time in June and July, 2018 had a lower tornado count than any other year over the past 13 years. Keep in mind the numbers are still preliminary over the past few months, so they are subject to change – likely less than the preliminary count. Until recently, this year was running closest to 2013 regarding the number of tornadoes. Clearly, the tornado count has been MUCH lower compared to recent years.
Late spring is typically the time of year for most tornadoes. Spring typically brings more severe weather episodes than Fall due to stronger temperature gradients, which leads to stronger storm systems and a stronger jet stream. Typically, the polar jet stream shifts north into Canada during the summer, leading to less tornado frequency.
We had a very interesting transition this spring from an extended period of very cold temperatures to a sudden pattern flip – this resulted going from the top coldest Aprils to the warmest May on record. The upper-level pattern in April featured a suppressed jet stream with a dry northwest flow over the typical tornado alley. Opposite of what you would want for severe weather. Oklahoma actually recorded ZERO tornadoes in January-April, something that hasn’t happened on record before. May featured a dramatic flip to the pattern with the jet stream shifted way north into Canada. This kept severe weather much less frequent and the magnitude much less than normal in tornado alley. The proximity of the jet in southeast Canada did bring an uptick in severe weather across New England.
April was the 13th coldest on record across the lower 48.
This was followed with the warmest May on record!
Just as we went from winter to summer and skipped spring, we had a dramatic flip in October from summer to winter! The extended cold weather has lead to minimal severe weather for November. This is the 11th coldest November for the U.S. since 1950! Check out the temperatures from normal across the U.S. for the month-to-date.
As we head into December and January, your greatest likelihood for tornadoes on average occurs across the Deep South. You may remember recently some big-time December severe weather events that occurred in the Deep South December 23-25, 2015, and December 25, 2012. Here’s hoping we keep the low tornado count going!
When more time allows, it would be interesting to take a look at weak El Nino years and see how those years evolve into the next spring regarding severe storm frequency and tornadoes. In next week’s blog we’ll target upcoming potential winter storm threats showing up. Thanks for reading, have a blessed day!
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