Saturday, August 15, 2009

One heckuva blow!

Last night just before dusk the weather service posted a severe thunderstorm warning (I get them on the computer). It was mostly out of my area and to the northeast so I didn't pay much mind as such warnings are a daily occurrence.

But then I looked out the office window and saw a huge, angry cloud rushing west to east. I went out with a camera. The picture shows a static mass, but it was far from that. It was moving very fast, swirling and roiling as it went. Then I heard a roaring of the wind and a low cloud came at me out of the southwest, more or less tangential to the big boy. It was dark and turbulent right down to the ground, roaring like a freight train, and shredding branches off the cottonwoods and scattering them around. I fled to the house, prepared to get the dogs and head for the shelter. But it passed as quickly as it came.

The lower pic was taken at the same time off to the east. Looks like a funnel cloud was trying to form but it never turned into anything.

Never a dull moment.


Mark B. said...

Rio, that's a cold-air funnel. They're generally caused by a down-draft microburst in a weakly organized cold front. They can -- briefly -- become tornadoes if they touch down, but almost never produce winds much in excess if 60 MPH or so. They don't have the "benefit" of the transverse wind shear necessary to generate the power of the real thing.

The wind you experienced was probably also a microburst. I'm assuming the afternoon was pretty warm and what passes for humid out your way. As the air mass warms it rises in the afternoon. Then an occluding cold front comes down over the top of the warm humid column of air and cools it so rapidly that the now-denser air starts dropping at relatively high speed. When it hits the ground it spreads out in all directions, producing an expanding circular wind front.

A couple of years ago, the center-pivot system near my home -- you may remember it -- got hit with a pretty healthy microburst that really mangled its outer 4 sections. There wasn't any rotation, just a heavy mass of air dropping down on top of it really quickly.


Rio Arriba said...

Excellent account, Mark. Thanks. I'm not a meteorologist, I just LIVE in the stuff!

BTW, we had another one the next day. During which Mags, who was out with me, ran away in terror. I got the Rhino out and drove around looking for her in a pelting prairie rain storm. She really loves her Rhino and finally came out from wherever she was hiding (I never did find out where) and ran up to be picked up. By then she looked like a little drowned rat. I was pretty worried.

Crotalus said...

DAYUM, but you have some mighty fine storms!