A cluster of deadly tornadoes struck north Texas on Wednesday night, killing six people.
This is an important reminder that although the severe weather season got off to a slow start during April and the first two weeks of May, that start offers little predictive value for what’s to come during the rest of May and June.
Typically the U.S. tornado season starts in the Gulf Coast states in the late winter, and then moves north with the warming weather, peaking around now and slowing down in July.
And it’s not just the threat of tornadoes. Along with twisters last night, these violent thunderstorms also brought massive hail to north Texas. How would you like to see this sucker falling out of the sky toward you?
Alas, there may be more to come.
According to NOAA’s Storm Prediction Center, conditions are ripe across the Plains states (see map) on Sunday and Monday for damaging winds, very large hail and possibly more tornadoes.
Now you may be wondering why Houston doesn’t get these very large tornadoes that often. There are several reasons, but first, let’s take a look at a map of tornado frequency in the United States.
Now Houston does get its fair share of tornadoes, but typically not those of the very violent EF3 or greater variety.
The reason is that there needs to be severe convection for tornadoes to form, and that will often occur where you have a collision between warm and moist air masses (such as those coming off the Gulf of Mexico) colliding with cold, drier air masses (such as those coming down from Canada).
In a blog post a couple of years ago, Cliff Mass did a nice job explaining a number of the factors that lead to supercells, which spawn tornadoes. And it turns out the most fertile breeding ground for these storms in the world is the Midwest. In summary, he wrote:
The High Plains, Midwest, and parts of the SE of the U.S. are “endowed” with large amounts of the key ingredients for severe convection — particularly during the spring. The results often range from tornadoes and hail, to intense precipitation and straight-line winds. One of the grand challenges of my field is figuring how to forecast these events … and it is probably the most difficult problem in meteorology.
Lucky Oklahoma and North Texas.