Thursday, April 22, 2010

Tornado Tips

Paul's Conservation Minnesota Outlook for the Twin Cities and all of Minnesota

Today: Sun fading behind increasing clouds, breezy and mild. Winds: SE 10-15. High: 68 (some thermometers near 70 by late afternoon).

Friday night: Showers, possible T-storms. Low: 50

Saturday: Showery rains, a few T-storms possible over southern MN. Winds: E 10-20. High: 57

Sunday: Showers taper, some PM sun possible. Winds: NE 10-15. High: near 60

Monday: Partly sunny, drier statewide. High: 63

Tuesday: Plenty of sun. High: 65

Wednesday: Clouds increase, showers possible late. High: 64

Thursday: Chance of rain. High: 65

Weather Nuggets & Factoids

* First spring without measurable snow in Duluth (!) Details from the Duluth NWS here.

* Live webcam of Icelandic volcano can be found here.

* Spring comes 10 days earlier now than it did just 20 years ago, according to a recent story in Reuters. Not hard to believe this year. It may be a trend...

* Will climate change bring about more volcanic eruptions? Trying to follow the (scientific) logic - not sure about this one, but keeping an open mind.

So, did you hear the sirens yesterday? There was a test of the emergency outdoor sirens Thursday at 1:45 pm, part of a mock tornado warning, to test the equipment, and get all of us thinking about what we would do, where we would go, if it was the real deal. This is Severe Weather Awareness Week in Minnesota - you can find a link to a week's worth of solid severe weather facts, guidelines and suggestions from the local National Weather Service office in Chanhassen here. Don't blow it off - just about the time you conclude that, "severe weather always strikes somewhere else....we NEVER see severe weather in our neighborhood...or....why do they always cry wolf? Tornadoes never strike here" - THAT - will be the day that Mother Nature provides a blunt reality readjustment.

People living in South Minneapolis weren't expecting a tornado touchdown August 19, 2009. There were no watches or warning nearby, the sky was ragged, threatening, light showers in the area, but the situation was hardly a classic tornado environment. Bands of showers moved through - I counted exactly ONE lightning strike from the cell that blew up over South Minneapolis, spawning a rotating wall cloud, then a funnel, then a tornado as the circulation touched down, whipping up winds estimated at 50-90 mph, a "minimal tornado," an EF-0 twister on the Fujita scale from 0 to 5. Then again, there really is no such thing as a minimal tornado. ANY tornado is a pretty big deal. It's an oxymoron, right up there with "airline food," "jumbo shrimp," and "Senate Intelligence Committee." Bottom line: technology is a wondrous tool, Doppler radar has saved countless lives, but it works best on the big tornadoes, the EF 2, 3, 4 and 5 storms. The small, brief tornadoes often get lost in the sauce, the "rotation couplet" is often too small to show up on Doppler, it is the meteorological equivalent of finding a needle in a haystack.

In the end, there is no substitute for common sense and situational awareness. "Mom, Paul's talking jibberish again!" Here's what I mean. The National Weather Service and local media will catch MOST of the big, violent storms, floods, hailstorms and tornadoes. But there will be some days where the best intentions and most powerful technology will be rendered all but useless by a freak weather phenomenon, something bubbling up that was not predicted or anticipated - and you will have to use common sense (and the severe weather rules you've learned over the years). By "situational awareness" I mean the ability to monitor the skies, constantly looking for tip-offs and tell-tale signs that severe weather is imminent.

Here are a few things to watch for:


1). Lowering, Rotating Cloud Base. Don't confuse a funnel cloud (rotating) with "scud", low, scrappy clouds that hang down from the cloud base - and are totally harmless.

2). Large Hail. The larger the hail, the more concerned I become. The reason: large hailstones require intense updrafts within a thunderhead, the larger the hailstone the stronger that updraft has to be (to keep those giant balls of ice aloft). When hail is golfball-size or larger I start to sweat, baseball or larger - a tornado may be imminent. Keep in mind that a tornado is a visibible manifestation of an especially violent updraft, one pulled down the surface. Big hail = higher potential for a tornado, which is not as much an object as it is a PROCESS.

3). Frequent Lightning: there is some correlation between the frequency of lightning and the ultimate severity of a thunderstorm. Nearly continuous lightning = greater risk of trouble.

4). Poor-man's Doppler. Bursts of static on the AM dial of your radio are evidence of thunderstorms within 100-200 miles of your home. If you hear nearly continuous static on the AM band a squall line, a line of especially intense/severe storms, may be close to home.

5). Rapidly falling barometer, south/southeast wind, dew points above 70. Tornadoes are most likely to develop around the dinner hour, along a warm frontal boundary, when the atmosphere aloft is highly unstable and highly "sheared" (changing wind direction/speed with altitude). While there's no way to look out your window and say, "Myrtle - there's wind shear out there - run for the hills!" you can keep an eye on the barometer on your wall. I have a fantastic barometer from La Crosse Technology, a digital weather instrument that tells me everything I need to know, as well as current warnings - my weather station even shows up on a web page. Very cool (and very useful/powerful). Check it out.

6). Green-Sky. You've heard this one before. Scientists still aren't exactly sure why the sky turns an eerie shade of green/yellow before a tornado - it probably has something to do with white sunlight being refracted (bent) by large hailstones suspended in the upper reaches of a thunderhead hovering overhead. That's conjecture - but if you see a green sky, make a mental note of the nearest shelter, basement, etc.

7). Where would I go - NOW? If you're at the new Target Field watching a Twins game, consider getting severe storm warnings on your cell phone (a number of good free options for getting e-mails and texts). I still get (free) e-mail warnings for the locations I care about from My-Cast, a service from Digital Cyclone, the company I started in 1999 and sold to Garmin in early 2007. BTW, for a few bucks a month you can get color Doppler radar, high-res satellite imagery, and wealth of other information on your cell phone. No, I didn't get a commission for that plug, I just believe in the product and the people that stand behind it.

8). Duck and Cover. The tornado itself won't kill you, it's what's IN the tornado, swirling around your head at 100-200 mph, that could put a crimp in your day. Most people are injured or even killed by blunt head trauma from flying debris. You need to get below grade, in a basement if at all possible, under the stairs is statistically the safest place to ride out a tornadic storm. No basement? Find a small room near the center of your house or apartment, like a closet or bathroom. Avoid outer walls and windows, avoid large rooms/auditoriums (first to collapse) and if you live in a mobile home make sure there's an underground storm shelter within a 1-2 minute dash of your front door. Winds exceeding 80-90 mph are often strong enough to turn a mobile home into a MOBILE HOME. In a vehicle, unless you can drive away from the tornado, your best bet is to hide in a ditch - not in or under your vehicle, but a ditch will provide the best odds of survival.

* About 15 years ago there was classic footage of a tornado chasing a TV news team; the reporter, photographer and a few motorists took shelter under a concrete bridge overpass. The tornado roared overhead (it was actually 1/8 mile away) but the footage gave the public the wrong message: hide under a bridge and you'll survive! Scientists have done tests since, and discovered that the risk of being hit by flying debris actually INCREASES if you're under a bridge, due to a "wind tunnel effect." It may be tempting - but avoid the urge. Personally I would find an exit and seek shelter in a gas station (small interior room, like a bathroom).

Downtown Tornado. On March 28, 2000, at 6:15 pm, an F-2 tornado ripped into DOWNTOWN Ft. Worth, Texas, killing 5, injuring over 100. The tornado struck after most people had already left work - or the death toll might have been much higher.

9). At Work. If you work in an office tower downtown you are just as vulnerable, in theory, as if you worked in the suburbs. It's just a matter of statistics and probabilities - a few high-rise buildings in the downtown core will NOT prevent a tornado from forming. Last year's August 19 twister passed directly over the Mpls. Convention Center, friends working in the IDS Tower reported seeing flying debris passing in front of their windows! Don't even think about using the elevators - find a concrete stairwell, or seek shelter in an interior bathroom, well away from outer walls and windows.

10). Avoiding Weather Trauma, How To Talk To Your Kids. Most TV meteorologists got into the business because they were somehow traumatized/frightened as kids, a tornado, hurricane, flood or other storm scared the crap out of them - they wanted to know more about what happened to them - they started studying storms, and this inevitably led to a career in meteorology. Think about it, who in their right mind wakes up and decides, "hey, I want to go on the air, predict the weather, and be WRONG a significant percentage of the time!"

Kids take cues from their parents - if you're cool, calm and collected, your kids will be too. If you panic your children will panic. I sat my boys down and explained severe weather safety rules, told them they would probably never need to use them, but "just in case, I'm going to tell you what to do." Liken it to a fire drill. It's an insurance policy. Kids (and adults) are scared of the unknown. If they know that "some storms are stronger than others, and if you do the right thing, follow the rules, you'll be fine", most kids will be just fine with that knowledge. It's the "not knowing" that presents the greatest challenge. The rules have to kick in on instinct - automatically - they should know that if skies turn threatening, even if the sirens aren't sounding, they should go to the basement and hide under the stairs or a work bench, or go into the bathroom, bathtub with a few pillows or blankets. Take nothing for granted.

Just like a fire-drill, take the time, explain it simply to your kids, and they'll be fine (and appreciate the fact that you spent the time and made the effort to keep them safer).

Significant Severe Threat. Severe thunderstorms are possible as close to us as Iowa later today (forming along a northward-advancing warm frontal boundary). A "moderate" risk of severe storms exists over the lower Mississippi River Valley, tornadoes more likely from Little Rock to near New Orleans, where the wind shear profile is ripe for "supercell" thunderstorms. Click here to go the SPC (Storm Prediction Center) web site.

Today will be the last lukewarm day of the next 3-4 days, a shot at 70 before clouds snuff out the sun later today - a growing risk of showers (even a few thunderstorms) tonight and Saturday as an intense area of low pressure slides off just south of Minnesota. The atmosphere overhead will probably be a bit too cool/stable for any widespread severe storms across Minnesota, although I can't rule out isolated cells capable of hail and damaging winds near the Iowa border.

Showers taper Sunday, if you have plans during the PM hours you may be ok, highs near 60 as skies brighten. Monday and Tuesday look dry with intervals of sunshine, temperatures still 5-10 degrees above average. Models are hinting at significant rain one week from today, a shot at low 70s the first weekend in May. Our amazing spring rolls on!

Saturday Puddles. The latest NAM model run (probably the most reliable/accurate) computer simulation prints out about a third of an inch of rain from late Friday night into Saturday, a few strong/severe storms possible as close as Iowa. It may be a close call.

Dueling Models. I think all the models are overestimating the rainfall potential for tonight and Saturday, amounts will probably be closer to .20 to .30" (unless heavy thunderstorms develop over southern Minnesota and stall overhead, in which case all bets are off). Dry weather is the rule most of next week, the chance of significant rain spiking again by Friday of next week.

Spectacular Solar Prominence. Activity is heating up (sorry) on the surface of the sun, NASA;s Solar Dynamics Lab has evidence of stunning solar flares (prominences) witnessed recently. To see the video clip for yourself click here.

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