One Type Of Drought To Love: A Lack Of Intense U.S. Tornadoes Lately

Tornado damage, minor, relatively speaking, in Tupelo,
Mississippi on May 3. There were no recorded violent 
tornadoes in May, 2021 AP photo by Thomas Graning

 It's been a busy year for weather disasters in the United States so far.

We've had crippling winter storms in February, frequent, extensive bouts of flooding in the South since March, big hail storms in Texas and elsewhere, and widespread drought in the West.  

One type of disaster that's been thankfully lacking this year, though, is violent tornadoes. 

May is usually the worst month for tornadoes in the United States.  This year, for the first time since accurate records on these things started in 1950, there were no tornadoes of EF-3 strength or worse.  EF-3 tornadoes have winds of 136 to 165 mph. 

Tornadoes are rated on six-point scale from EF0- to EF-5, with the fives being the worst. The great majority of tornadoes in the U.S. are weaker EF-2 or less. These weaker ones have winds of 65 to 135 mph. 

The ones that tend to grab headlines are the EF-3s to EF-5s, which, if they hit a populated area, cause terrible destruction.

Most years, there's at least a few scattered EF-3s, 4s, or even 5s somewhere in the United States. Unless re-analysis proves otherwise, this will be the first May on record without anything so destructive 

There was actually about an average number of tornadoes across the United States in May.  We have 289 reports of tornadoes, says NOAA's Storm Prediction Center.  The average is around 272, so close

Even the relatively strong EF-2 tornados were lacking in May. So far, there were only eight such twisters confirmed during the month. That's the fifth fewest on record for May, says the SPC.  That means almost all U.S. tornadoes in May were pretty weak, and didn't cause all that much damage.

Here's an even better piece of good tornado news: For the first time since 2014, there were no tornado deaths in the United States for the month of May. 

We also broke another, very welcome tornado record. As of yesterday, it's been eight years and 21 days since the last time an EF-5 tornado hit the United States.  That's the longest we've gone without the strongest tornadoes we can get.

EF-5s are the real monsters of the tornado world, being the strongest they can get. They produce winds of over 200 mph. In these strongest tornadoes, entire homes are swept off their foundations and swept away.  Cars and car-sized debris are blown 100 yards or more through the air. Bark is removed from trees and pavement can be sucked off roadways and parking lots. 

You wouldn't want to be caught in one of these. 

Luckily, with this new record means that nobody has been caught in an EF-5 tornado since May 20, 2013, when an EF-5 swept through Moore, Oklahoma. That tornado killed 24 people and caused at least $2 billion in damage.

There's not a clear reason why the United States has not endured an EF-5 tornado since Moore.  One good theory, writes Bob Henson in Yale Climate Connections,  is that there actually been one or more EF-5 tornadoes since 2013. We just don't know it. 

The strength of tornadoes are determined in post-storm analyses. Meteorologists look at damage to buildings, trees, and other items, and figure out from the damage how strong the tornado was.

But if an EF-5 tornado lumbers through the wide open Great Plains without hitting anybody's house or property, it won't be designated as such because there's no damage assessment to be done.

It could be just dumb luck that EF-5 tornadoes in recent years detoured around towns and farms and patches of woods in the otherwise grassy prairies. 

Tornadoes attract zillions of storm chasers, and some of these chasers bring radar equipment. Their radar has detected likely winds of 200 mph or more in some twisters in remote areas since 2013, so the idea that there are uncounted EF-5s is pretty valid. 

There's no telling when the drought of strong tornadoes will end, but it could end on a dime. 

We've had a similar experience with hurricanes, notes Henson in Yale Climate Connections. No strong hurricanes hit the U.S. from October, 2005 until August, 2017, the longest period we've had without such big storms.

Then Category 4 Hurricane Harvey hit Texas in August 17, and since then the U.S. has been hit by five major hurricanes. 

With that in mind, it's probably just a matter of time before the United States deals with another tornado tragedy like that in 2013 Moore, Oklahoma.