Severe Thunderstorms and Microbursts

Any thunderstorm can be dangerous, but severe thunderstorms must meet these guildelines:

• Have winds of at least 58 miles per hour or stronger.
• Or, produce hail 3/4 inch in diameter or larger.

Microburst

Severe storms can also produce torrential rain, frequent lightning, and even tornadoes.

However, most wind damage in East Tennessee occurs not from tornadoes, but from a microburst or collapsing thunderstorm.

On February 11, 2009, our area experienced just such a storm. Most of the damage caused by it was from microbursts.

These storms create straightline wind damage. To consider how that happens, imagine of the strong winds from a mature thunderstorm rushing down out of that storm and hitting the ground. That energy hits the ground and spreads out in all directions, pushing trees and other items over in it's path.

Water poured from a bucket

It's not uncommon for these winds to be well over 100 miles per hour, which is hurricane strength.

Here's another way to think of how a microburst is created. Picture a bucket of water as the wind racing out of a thunderstorm. When the water from the bucket (or wind from the collapsing thunderstorm) hits the ground, it pushes all the objects over in the same direction creating a well-defined damage pattern.

Microbursts are totally different from tornadoes. The damage from a tornado is in more of a twisted pattern of debris.