As tornado season begins, an expert weighs in

Friday, it was cold enough for a few snowflakes to fall in Southeast Missouri. By Sunday afternoon, people were comfortable outdoors in shorts and T-shirts, as temperatures hovered in the mid-70s with nightly temperatures rising 30 degrees in that short span.

This is not unusual in the American Midwest. Warm air from the Gulf of Mexico slams into cold air flowing down from Canada.

These air-mass collisions cause severe weather -- thunderstorms and tornadoes -- most commonly found in the so-called "Tornado Alley." The Midwest is home to more tornadoes than anywhere else on the planet.

Harold Brooks is a senior research scientist at NOAA National Severe Storms Laboratory in Oklahoma City. NOAA is the National Oceanic and Atmospheric Administration, tasked with tracking and studying dangerous storms, including the super cells that generate the most powerful type of twister.

He said the recent temperature variation set the table for potentially severe weather.

"What that's meteorologically saying is, we must be having really strong southerly winds, bringing back warm moist air to create that cold-to-high transition. We can also infer a dip in the jetstream above us. We can start to set up ingredients for a storm," he explained.

Those elements have combined for a three-day severe weather event. Severe thunderstorms and several tornadoes rolled through Oklahoma and Arkansas on Monday. Tuesday, the severest weather was in Texas.

Storms today will have Missouri in their sights, according to NOAA's forecast.

"Numerous severe thunderstorms appear likely across a large portion of the lower/mid Mississippi Valley into the Midwest, and lower Ohio Valley on Wednesday. Damaging winds, some of which could be significant, several tornadoes (some strong), and large to very large hail will likely occur," its forecast said Tuesday afternoon.

Unpredictable

A Missouri native with familial ties to Southeast Missouri, Brooks went from storm chasing in his youth to generating complex computer models of severe thunderstorms at the University of Illinois, pursuing his doctorate.

"The tornado problem is interesting in a lot of aspects," Brooks said. "How do we forecast them? How do we understand them? How should people respond to them?"

Brooks has touched on all these interconnected questions at different points in his life. Although he hasn't physically chased a storm since 2010, he still hunts them with technology.

"... [T]he really big thing actually, for us, is radar. Particularly Doppler and the networks that were deployed in the '90s. If I want to, I can look at the rainfall and velocity pattern of any storm, anywhere in North America, at any time," Brooks said. "[Radar] lets us see what's going on inside the storm. Other countries have individual radars. We have a network that's pretty unique and allows us to experience the storms in a different way."

Deadly

Missouri is no stranger to deadly tornadoes

The deadliest tornado in U.S. history, the Tri-State Tornado of 1925, which formed in Southeast Missouri. Brooks said it touched down somewhere in Reynolds County, west of Ellington, and crossed the Mississippi River south of Perryville.

In May 1949, a raging F4 tornado walloped northwest Cape Girardeau, crumbling more than 200 homes and killing 22 people. The same day, an F3 swung from north of Marble Hill to eastern Oak Ridge, killing a man who ran from his car seeking shelter.

Tornadoes in Southeast Missouri are less predictable, occurring at off-peak-season times more often than in more traditionally active areas for tornadoes.

"Tornadoes have been observed in all 50 states, and the only continent we haven't seen one on is Antarctica. With very rare exceptions, the distribution of tornado intensity is the same everywhere you go. For every one thousand tornadoes that occur, roughly 100 of them are F2 and stronger. About 1% are F4 and higher. That's true pretty much everywhere you look," Brooks explained.

Precautions

Brooks encouraged those in the path of severe weather to take safety precautions.

"I don't expect people to listen intently to every weather forecast issued every day, but you do need to have a plan," he noted. "You don't want to be in a mobile home or a car. You want to be ready to receive information and then take action if necessary. You want your place of safety to be as low and interior as you can be. Put as many walls between you and the tornado as possible. If you have a bicycle helmet, put it on."

If you find yourself away from home when a tornado approaches, Brooks suggested finding shelter in a well-built building.