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Weathercatch: Severe weather events – there’s something about May

May kicked off with a bang in the eastern U.S., the southern and Plains states, bringing a mix of tornadoes, hail, strong winds and violent thunderstorms. In our region, it was more like a soft knock. A few passing thunderstorms but nothing more.

Driven by the seasonal rise in temperatures and humidity, the severe weather season arrives each spring. Tornadoes slice across Oklahoma and Alabama; powerful thunderstorms hammer Michigan to Maryland.

But our area is pretty much isolated from these kinds of intense weather outbreaks. Most of us have never experienced the ferocity of a tornado or a band of violent thunderstorms.

If we have a severe weather season, it’s quiet compared to much of the country. While tornadoes and severe storms occur here, they’re rare. And when they do strike, they’re generally isolated and short-lived. If you ever witnessed a series of storm clouds pile up to form a squall line, it was somewhere like Arkansas or Ohio, not here.

A key ingredient that’s missing in our region is humidity – water vapor in the lower layer of the atmosphere. Air circulating off the Gulf of Mexico is warm and moist, compared to the cool air moving off the Pacific Ocean. And because cooler air holds less moisture than warm air, there’s less fuel to kick-start thunderstorms and fewer thunderstorms capable of spawning tornadoes.

As a cluster of severe thunderstorms moves across the central U.S. this week, we’re sitting pretty under calm blue skies and warm temperatures. But that’s not to say thunderstorms packing strong winds couldn’t come our way.

Historically, there’s a slight bump of bad storms during May. Here are some examples:

May 1, 1991: What a newspaper described as a “strange-looking mass of black clouds” released a tornado near Genesee, Idaho, on May 1.

May 17, 1996: Lightning struck a house in Moscow during a thunderstorm, blasting a hole in the roof and igniting a fire.

May 19, 2004: A late-afternoon tornado touched down in East Wenatchee, followed by penny-sized hailstones.

May 21, 2004: A late-afternoon tornado touched down near Fairchild Air Force Base during a storm that produced lightning, hail and heavy rain to Spokane County.

May 6, 2009: A thunderstorm dropped a tornado north of Davenport, Washington, in Lincoln County, snapping trees and scattering debris across a 6-mile swath.

May 29, 2015: Severe thunderstorm warnings issued by the National Weather Service panned out that night when storms delivering lightning and up to 53 mph winds caused power outages and minor hail damage to cars in Spokane and Lincoln counties and the Idaho Panhandle.

So is there something about May? The month tends to promote the periodic convergence of factors such as moisture, instability and a lifting mechanism known as an updraft that produces occasional thunderstorms and even tornadoes in our region.

Nic Loyd is a meteorologist with Washington State University’s AgWeatherNet. Linda Weiford is a WSU news writer and weather geek. Contact: linda.weiford@wsu.edu or nicholas.loyd@wsu.edu.


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