Sunday, March 27, 2016

Wowed By Wet Microbursts. Stay With Me Here!

Photographer Peter Thompson captured these
images of a wet microburst in
Queensland, Australia. You can see
how these things look like scary "rain bombs"
It's Easter Sunday, and the nation is being blessed with largely uneventful weather today.

Oh sure, there are trouble spots. There could be some severe thunderstorms in and near Indiana today. Flash flood watches are up for parts of the Gulf Coast, and there's high wind alerts in the Desert Southwest.  

But luckily, there are pretty much no epic storms or extremes to pester us today.

This lack of activity gets my mind wandering a bit, and since we are getting into the spring and summer severe thunderstorm season, I happened to find some stuff on something called "wet microbursts" today.

Wet microbursts are an underreported player in severe thunderstorm destruction, outgunned by photogenic tornadoes, hail and lightning.

These wet microbursts are usually hidden within curtains of rain, but they are responsible for a large share of damage caused by severe thunderstorms.  There are a couple of great videos at the bottom of this post that do manage to capture the drama of wet microbursts.

There's no particular "wet microburst alley" in the United States where they are most common. They can happen practically anywhere, and have raised havoc pretty much everywhere.

Strong updrafts in severe thunderstorm suspend large amounts of raindrops and hailstones up in the the core of the storm.

After awhile, the updraft in the storm weakens, and is no longer capable of holding all that stuff up there. Suddenly, then, all that rain and hail plummets to the ground really fast. 

Where it hits the ground, there's an incredible blast of wind, incredibly torrential rain and often hail. When the gush hits the ground, the wind blows outward from ground zero in very strong gusts. There's always a zone of damage, maybe two miles across, with the ground zero spot understandably having the worst damage.

Winds can easily and far exceed 100 mph in a microburst, so they can be as destructive as tornadoes. That's why you shouldn't relax when there's "only" a severe thunderstorm warning, instead of a tornado warning.  You don't want to be caught outside in a microburst.

Incredible amounts of rain usually accompany wet microbursts, so flash flooding is often a problem with these things, too. Wet microbursts are basically violent rain bombs.

You often don't get as much lead time in a warning about a microburst as you often would with a tornado. Wet microbursts often develop suddenly. Forecasters will often know 12 hours or more in advance that the weather is favorable for microbursts, but are usually not able to tell exactly where they will happen until just before or during the event.

Weather that is conducive to these microbursts is when it is hot and humid near the Earth's surface, where we are, and it's chilly, windy and quite dry in the middle layers of the atmosphere high overhead.

Last August, storm chaser and photographer Brian Snider captured on a really cool video a destructive wet microburst around Tucson, Arizona. Here's some time lapse videos of it and a narrator explains what's going on:

Proving that you don't want to be outdoors in a microburst and that destructive microbursts often happen well outside of tornado alley, here's a security camera view of a July, 2014 wet microburst in the northern New Hampshire town of Littleton:

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