Kevin Myatt

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About Kevin

Kevin Myatt grew up in Arkansas to the tune of tornado sirens and the rhythm of hailstones, aspiring to be a meteorologist before his studies and career were turned to journalism instead. Though he often chases storms, he prefers living in the cooler, more tranquil weather of the Blue Ridge. He moved to Roanoke in 1999 to take a job on the copy desk of The Roanoke Times; writing headlines and editing copy is his principal work for the newspaper today.

Each May, Kevin assists Pulaski County High School / Virginia Tech meteorology instructor Dave Carroll in leading college and high school students to the Plains to observe severe weather firsthand. The accounts of many of his storm chases can be found here on the storm chasing page of his weather blog on roanoke.com.

Kevin was an editor for "Hurricanes and the Middle Atlantic States," a book written by D.C.-area weather enthusiast Rick Schwartz and published by Blue Diamond Books that documents hurricanes striking the mid-Atlantic states since colonial times.

The Weather Journal column began in 2003 and appears on Friday's Virginia section front in The Roanoke Times. The Weather Journal blog began in 2006 and follows weather day-by-day between the larger columns.

Spring bigger for storms than fall

We didn't get nearly enough rain Friday to ease our drought. We also didn't get the big thunderstorms we could have, with the cold front moving through when the atmosphere wasn't very unstable.

But many parts of the nation experienced severe weather this week, with a deadly tornado in Missouri and widespread reports of damage from high winds throughout the Plains, Midwest and South.

It is not unusual for there to be an upsurge of severe weather for a few weeks each fall, as cold air from the north begins again to clash with warm air from the south.

But severe thunderstorms and tornadoes aren't usually as big a deal in the fall as in the spring, even though both seasons are known for shifting weather patterns between warm and cool.

Why is spring more volatile for severe weather?

There are a few reasons, but one of the biggest has to do with the preceding season.

A key ingredient for big storms to fire is instability.

Instability refers to the ability of air to rise in the atmosphere. That means a cold air mass sits on top of a warmer one, so that the rising warm air can bubble up into it. The bigger the difference in temperature, the more unstable the atmosphere is.

In the fall, cool air gradually invades the United States after the heat of summer. Much of the atmosphere has been heated by rounds of hot sun under high pressure systems.

Because the upper atmosphere tends to be warm from lingering summer heat, that warmth aloft can retard air at the surface from rising up into it. That is called convective inhibition or, more simply, a cap.

In the spring, the atmosphere has been chilled from months of Arctic air masses moving down during winter. Warm air gradually invades the United States from the south.

The upper layers of the atmosphere are cold, and as a result, warm air moving in at the surface can rise more readily to raise up storms.

So the spring severe weather season in the central and Eastern United States often lasts for months, typically March to June, as the atmosphere gradually warms and the jet stream slowly shifts back to Canada.

The severe weather period in the fall may be only a couple of weeks as the atmosphere cools, and some autumns pass without any widespread severe weather occurrences in the United States. Severe weather outbreaks in the fall are usually caused by storm systems resembling their spring brethren, large low-pressure areas that sweep up warmth and Gulf moisture at the surface before swinging a cold front through.

So fall often has to look more like spring for severe storms to occur. That's what we've seen the past week across the United States.

It's a fall so far that hasn't looked much like fall -- first like summer, and now more like spring. The next couple of weeks may see some shifts that bring more fall-like weather to much of the central and Eastern United States.

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