Not in Kansas Anymore

Spring is in the air. The return of warmer weather also brings thunderstorms and the start of tornado season, so there's a lot more in the air than just spring. You might associate tornadoes with places like Kansas or Oklahoma, but tornadic activity usually starts in the South in early spring. By May or June, the center of activity moves west to the Lower Midwest, then shifts to the Upper Midwest for June and July. However, tornadoes can strike anywhere at any time. The previously mentioned periods are just the most likely times and locations. Here’s some information about this swirling vortex of death.

Swirling vortex of death (National Weather Service)

The current theory on how a tornado forms is that differing wind speeds during a thunderstorm cause horizontal rotating air columns. If the air column gets caught in an updraft it changes orientation and becomes a vertical column. If the column touches the ground it’s a tornado; otherwise it’s just a funnel cloud.

Tornadoes primarily form in supercell thunderstorms, which are large rotating thunderstorms. Tornadoes will likely drop from a feature of the storm called a wall cloud, which is large low-hanging cloud to the rear of the area of precipitation. It’s far easier for ground spotters to in the Midwest to see wall clouds and storm rotation from a distance than it is for those in other areas.

Wall cloud (National Severe Storms Laboratory)

Having lived in Pennsylvania and Washington all my life, there is no clear horizon in my areas. There are trees, mountains, and buildings in the way. I could tell if a storm was coming based on the clouds in my immediate area. Driving across northern Wyoming, I could see a pair of thunderstorms miles away and the precipitation was visible long before I caught up to it. I didn’t see any rotation or wall clouds, but I was also focused on the road.

Signs to look for during a potentially tornadic thunderstorm are hailstones, green clouds, rotating and/or low hanging clouds, and the loud roar of a freight train. If you observe any or all of these signs, seek shelter immediately.

Another twister (National Severe Storms Laboratory)

Tornado safety

When a tornado watch is issued, it means conditions are favorable for tornado formation. A tornado warning is issued when radar indicates rotation in a storm or a tornado has been seen by a spotter in the field. If a tornado warning is issued, seek immediate shelter. The best place to be is in a basement, but absent that use the downstairs area of a building. A windowless room is best. If there is no windowless room, stay as far from windows as possible. If you can, get under a sturdy table or cover yourself with heavy blankets. If you’re in a high rise, seek shelter in an interior hallway on the lowest floor possible. If outdoors, try to get inside. If you can’t try a vehicle. Buckle up and cover up. Lying in a ditch or depression is also a viable option. If driving, don’t try to outrun a tornado.

This week’s tornado information comes from the National Severe Storms Laboratory and University Corporation for AtmosphericResearch. Safety tips come from Ready.gov.