Late May Often Terrible, Dangerous Time For Tornadoe. Not This Year

A deadly EF-5 tornado in Moore, Oklahoma, May, 20, 2013. This was
the most recent  EF-5 tornado recorded in the United States.

As I do every year for about a week to 10 days, I've moved myself and this here blog thingy out to the lovely little city of Yankton, South Dakota. The main reason to do this is to visit my outlaws, er, I mean inlaws.

Southeastern South Dakota is also a decent vantage point this time of year to observe spring thunderstorms. And they're often severe. And there's sometimes tornadoes here and there.

That might be the case this year, but I'm not counting on it. Which is a good thing. Tornadoes are dangerous, after all, and like I said, Yankton is lovely, and I'd hate to see any damage here.

As I think I've mentioned before, this remains a slow severe weather season, with a definite dearth of tornadoes, notwithstanding the nine tornadoes that struck the Northeast last week,

Often, during the final 10 days of May, there are very, very often dozens of tornadoes spinning out of the supercells and storm complexes that typically cross the nation this time of year. There were pockets of severe storms yesterday, but nothing spectacular.

Devastation from an EF-5 tornado in Parkersburg, Iowa in 2008

One weak tornado was reported Monday in Colorado, and it caused no damage. Some places had strong winds and hail, particularly in Colorado, New Mexico, Ohio and North Carolina.

Today and tonight, there will be new pockets of severe storms, especially in and near eastern Ohio and western Pennsylvania. Also, there might be some, especially tonight, in parts of the northern and central Plains, including here in Yankton.

But the tornado threat is very low, and these patches of severe storms won't be nearly as extensive as they often are this time of year. The rest of the week also looks quiet.

This is a huge contrast to many late Mays. The devastating Moore, Oklahoma EF-5 tornado, for instance, came on May 20, 2013. And thirteen days later, an immense 2.6 mile wide tornado in El Reno, Oklahoma killed storm chasers trapped in its path.

On May 29-31, 2004, a total of 170 tornadoes killed five people and injured 150 people in 16 states.

On May 23, 2008, 80 tornadoes touched down in just Kansas alone, and two days later a huge EF-5 tornado wiped out much of the city of Parkersburg, Iowa. 

Stunned survivors after the EF-5 tornado in Joplin, Missouri, May 22, 2011.

On May 31, 1985  30 tornadoes touched down, mostly in Ohio and Pennsylvania. This included an EF-5 tornado, the strongest you can get, that pretty much wiped out Wheatland, Pennsylvania. (the Moore tornado was EF-5, too.)

We also can't forget the EF-5 tornado that devastated Joplin, Missouri on May 22, 2011, that killed 161 people.

Notice I'm mentioning all these EF-5 tornadoes that often come this time of year. These are the ones that make most of the tornado news every spring or summer. They're rare. The United States has had only 59 of them since 1950. But EF-5's cause the most damage and are the most deadly. These are the worst tornadoes you can get, with winds of over 200 mph.

There's a couple videos of EF-5 tornadoes at the bottom of this post to give you an idea of how scary they are.

The nation, mercifully is now in one of the longest streaks in history in which no EF-5 tornadoes touched down The last EF-5 tornado the nation endured was that Moore twister in 2013. That's five years without such a tornado. That's the second longest period of time we've gone through without such a strong tornado since 1950. (There were no EF-5 tornadoes in the eight year span between May 3, 1999 and May 4, 2007.)

Regular tornadoes are also in relatively short supply this spring. So far this May,  there have been 52 confirmed tornadoes in the United States. During the entire month of May, there's typically more than 200 tornadoes in the U.S.

Greensburg, Kansas was destroyed by an EF-5 tornado in 2007

So why has this May been so benign in terms of tornadoes and other severe weather?

And why has each year since 2012 been relatively calm in the tornado department? Unlike many climate trends, I don't think we can clearly pin climate change on this fortunate turn of events.

It's probably just dumb luck. This year, the first part of spring was dominated by blasts of Arctic air that suppressed the warm, humid air needed for tornadoes well to the south. So there was not much severe weather back in April.

In late April and early May, the weather pattern shifted dramatically and abruptly toward a summer pattern. The jet stream, which energizes storm systems, usually comes across the middle of the country this time of year, helping spawn severe weather outbreaks.

This year, the jet stream shifted far north, mostly over southern Canada or the extreme northern United States where it usually resides over the summer.  That means there's not as much energy to produce big storm systems.  Which means we just have relatively small weather disturbances that produce modest outbreaks of severe storms.

You can still get a lot of severe weather in June, and in the northern United States in July and August, so we're not out of the woods.

But in a time period over the past five years in which the United States has endured incredibly severe wildfires, deadly floods, severe winter storms and, last year, devastating hurricanes, the general lack of tornadoes and severe thunderstorms is a gift.

Here's a video of the Moore, Oklahoma tornado on May 20, 2013 as it rapidly intensified from something small to an EF-5 monster:



Famous surveillance video of the EF-5 tornado blowing away a house in Parkersburg, Iowa
back in 2008:



Storm chaser Jeff Piotrowski and his companion go from excitement to terror to horror as they watch an EF-5 tornado destroy much of Joplin, Missouri.