Kevin Myatt is The Roanoke Times' weather columnist.

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When I was a young teenager at home in Arkansas, there was a storm one early evening that seemed like one of the mightiest I had ever seen.

Trees bent over double and limbs flew off on a strange east wind, accompanied by a downpour of rain, that lasted just a few minutes. As quickly as it started, it was finished.

I couldn't wait to see the 10 p.m. newscast to see what other damage this monstrous storm had wrought across the area. But there wasn't a word about it, or even any acknowledgment that there had been severe weather of any significance anywhere around.

You may know the feeling, if you've ever talked about big thunderstorm winds doing something on your property and other people looked at you as if you were crazy, or said something like: "What, that little thundershower did that?"

Wet microbursts, as these short-lived and highly localized blasts of wind and rain are known, are probably our area's biggest severe weather threat in the summer. The atmosphere is often too warm for large hail to form, and strong upper-level winds changing with height necessary for long-lived supercell thunderstorms and tornadoes are rarely present.

For wet microbursts, you just need some heat and moisture, and little else.

The principle is simple. Every thunderstorm is a system of updrafts and downdrafts. A microburst is an extremely intense but relatively small downdraft.

As warm, moist air lifts upward into a thunderstorm, it eventually reaches a cooler, drier layer aloft. The moisture evaporates in the dryness, cooling it further.

Eventually, what was a dry layer becomes saturated with moisture, and it also becomes much cooler from the evaporation that has taken place. Cool air is denser than warm air, so it begins to plunge rapidly through the storm to the surface. The weight of moisture, falling as rain and sometimes hail, adds an extra push.

Finally, it blasts to the ground as tree-bending winds and torrential rain. Winds in exceptional events can exceed 100 miles per hour and leave structural damage comparable to a moderate-intensity tornado. More commonly, the winds gust up to 70 mph, still enough for considerable damage.

People hit by a microburst might think it's a tornado. There can be an awesome roaring sound and even a cloud formation similar to a funnel, pushed downward from the cloud to ground by the rush of wind and precipitation.

But the key difference in a microburst and a tornado is that there is no vertical rotation in a microburst. Microburst winds can roll like a barrel along the surface, creating intermittent periods of damage a few miles away until surface friction eventually slows the winds down, but the downdraft itself does not rotate. A tornado, by comparison, is a rapidly spinning updraft.

Microburst damage spreads outward from a central point, while tornado damage spins toward a central point.

There are "dry microbursts," too, though these are more common in the West where high storm bases and more dry air below the storm can cause any precipitation falling with a downdraft to evaporate before hitting the surface.

Microbursts have been connected to many plane crashes over the years, though weather radar improvements have lessened the problem because they are easier to detect and steer around.

On Aug. 1, 1983, the strongest microburst wind gust on record was clocked at Andrews Air Force Base in Washington, D.C. -- 149.5 mph, or the strength of a strong Category 4 hurricane. President Ronald Reagan had landed there in Air Force One just eight minutes earlier.

See photos from Thursday's storms on Kevin Myatt's Weather Journal blog at blogs.roanoke.com/weatherjournal/