Author Topic: Microburst?  (Read 5402 times)

Elle

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Microburst?
« on: January 09, 2009, 07:37:44 pm »
Just reading through Cry Wolf and came across this passage:

...they reached a small bench of land littered with downed trees.

"Microburst last spring, maybe," he told her. "It happens sometimes."

I had to google microburst. I'd never heard of such a thing...is it a frequent phenomenon?
« Last Edit: January 22, 2012, 06:11:55 pm by Elle »
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Mike Briggs

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Re: Microburst?
« Reply #1 on: January 09, 2009, 07:55:46 pm »
Microbursts are fairly common in the western states, and are often associated with tornados in the midwestern states.  In the mountains of montana, they're usually associated with thunderstorm activity, particularly dry thunderstorms.  Basically, you have a column of cold, dense air that drops like the hammer of God through warmer air layers below it, gathering speed.  Then it hits the ground, and spreads out.  Eventually the spreading winds kind of curl back upwards, and the air density equalizes, and the whole thing peters out -- usually the intense part lasts just a few minutes. 

However, the trick is that you usually can't seem them coming, and they can hit like a mini-tornado.  Ok, not quite so bad as all that, but windspeeds are often more than 50mph, and sometimes as much as 70.  Because they can "drop in" to areas normally shielded from lateral winds (where trees tend to have less-entrenched root systems) microbursts have a reputation for toppling trees.  In the forest, you'll occasionally see fairly small areas (1/2 mile diameter or so) with broken, twisted trees thrown about, branches snapped off, and all manner of chaos while all around that area everything is pristine.  That's the signature of a strong microburst.

Does that help?
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opramum

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Re: Microburst?
« Reply #2 on: January 11, 2009, 07:43:32 pm »
We had one run through here (up from Hermiston Ore through the Tri Cities, Mercy's stomping ground) a few years back.  Right before harvest, dumping on crops and cutting a swath a  hundred yards wide or so.  Was really strange to drive through these beautiful fields and poplar farms and suddenly there was utter devastation for just a short time.
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Dobbythehouseelf

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Re: Microburst?
« Reply #3 on: January 12, 2009, 03:20:05 pm »
So could a microburst occur in the winter?  And assuming a person was at ground zero so to speak when a microburst came down how would they fair?

opramum

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Re: Microburst?
« Reply #4 on: January 12, 2009, 03:25:47 pm »
Here is a link to a video of a description of a microburst, and a video of a microburst.  I was surprised at how many videos there are.

http://www.youtube.com/watch?v=TkavH9aZue8
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Mike Briggs

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Re: Microburst?
« Reply #5 on: January 12, 2009, 04:48:07 pm »
Microbursts vary considerably (just like all other weather phenomena).  I love storms, and have been out in several microbursts, though I'd seriously run from a tornado.  The problem, generally, is that you don't really see them coming.  I remember seeing a very small one hit one of our pastures when I was a kid.  We were up on a hill, looking down at the pasture as a storm hit, and suddenly you could see a rough oval of grass get smashed flat, and all the way around the grass was being blown away from the center.  It wasn't terribly strong, and didn't tear up too much of the grass.  It only lasted a few minutes, but later you could see where all of the grass had been flattened, kind of like a particularly uninspired crop circle.   Usually they're a little bigger, and it's hard for someone on the ground to know for sure if the winds they're feeling are part of a microburst, or just the usual winds associated with a thunderstorm.

The biggest danger to people is falling trees or high-speed debris; just like a tornado, hurricane or any other high-wind event.  Generally, they're short lived but intense, and the wind will definitely be directional (unlike tornadic winds, which change direction).  If you find something nice a solid and just get out of the way (which is pretty much instinctual when dust, rocks and whatever are being hurled at you hard enough to hurt), you're odds are very good.

I'm sure microbursts have killed people, but it's probably not often. We had one just disintegrate a garden shed at our Butte house, and I'm glad it missed the house!  It was a Rubber Maid shed, fastened to railroad ties sunk into the ground.  We found bits and pieces of it scattered over most of the 40 acres, torn apart like paper mache. That said, MOST of them don't have really dangerous wind speeds, they're more exciting than deadly unless a tree falls on you!




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