Thursday, June 18, 2009

Ripe for Isolated Tornadoes

** Amazing YouTube clip from yesterday's Austin tornado (thanks to Brad Nelson from DTN for making this available to WeatherNation and its clients). Click here to see some breathtaking scenes of the "chase"!

Update: 1:05 pm. Severe storm warning posted for western Douglas county until 1:45 pm for quarter-size (1" diameter) hail. The cell is moving northeast toward Evansville. People living in the Alexandria/Carlos area should be prepared to move to shelter. Although no tornado watches are currently in effect we can't rule out an isolated tornado with this cell - although the greatest danger will probably come later this afternoon, after 3 or 4 pm, when the atmosphere overhead is most unstable. Keep checking in for more updates.

(remember to click on the image below to see it full screen, so you can see all the details and read the text of the NWS warning!)

The latest from SPC, the Storm Prediction Center, showing a MODERATE risk of severe storms extending into almost all of central and southern Minnesota. With high dew points, an unstable atmosphere, strong "wind shear" aloft and boundaries left over from last night's storms, conditions are ripe for more potentially violent weather later today and tonight. I do expect watches and warnings to be issued by mid afternoon, the threat of large hail and isolated tornadoes increasing as you head south toward the Iowa border. Statistically, there is a 5-10% probability of a tornado within 25 miles of any town south of St. Cloud through the late evening hours. Stay alert, check back to this site often for updates (including Doppler radar and warning information on a county by county basis). I'm pretty confident there will be more tornado touchdowns around the dinner hour - hard to pin down which part of the state has the highest risk of violent weather - hopefully that will crystallize over the next few hours.

In a tornado the safest place to ride out the storm:

* Basement, under the stairs. Statistically this is the safest place to be, under a desk or heavy piece of furniture if possible.

* Small, windowless room on the ground floor, like a closet or bathroom. People have survived F-5 tornadoes by hiding in their bathtubs, a mattress or blanket (or pillows) on top of them.

* Avoid outer walls/windows. Most tornado injuries are the result of flying debris and head trauma. That's why it's preferable to get below grade, underground if at all possible.

* In a school or office seek shelter near the interior of the floor, a concrete-reinforced stairwell or bathroom usually provides the best protection.

* Avoid mobile homes (which can become airborne at wind speeds as low as 80 mph). Avoid large rooms, gymnasiums, auditoriums - these are the first to collapse when a tornado hits.

* In a vehicle you can usually drive away from the storm. If that's impossible get out of your vehicle and seek shelter in a nearby building - OR - a ditch. Do NOT ride out the storm inside a car or truck or underneath a vehicle. Do NOT seek shelter under a bridge overpass (a wind-tunnel effect can increase the threat of flying debris hitting you there).

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