Monday, April 19, 2010

Sliding into a stormier pattern (by the weekend?)

This is Severe Weather Awareness Week in Minnesota, a chance to review severe weather safety tips with loved ones (or complete strangers, if you're at an awkward loss for words). On average Minnesota experiences about 30-40 days/year with thunder & lightning, 2-4 days with large hail, an average of 25-30 tornadoes skip across the state, and odds favor at least a half dozen or more flash flood events during the warm weather season. Odds are you won't be personally affected, but just when you think "no need to worry, I never see anything dangerous", that will be the year your neighborhood is struck.

Last summer's tornadoes in Mound, Orono and South Minneapolis were blunt reminders that tornadoes CAN AND WILL FORM IN THE METRO AREA. I continue to be amazed by the number of otherwise bright, rational adults who believe that, somehow, "the metro area doesn't see tornadoes - they only touch down in farmland," - or - "I live next to a river or lake, tornadoes can't cross bodies of water (or hills!)" Tornadoes have formed in every state of the nation, even Alaska and Hawaii - on rare occasions tornadoes have been known to track over snow-covered fields in the Rockies, although this is a VERY rare occurrence. The presence of a lake, river, a few high-rise buildings in a downtown, is NOT a deterrent to nature's most violent wind. A violent updraft, which is all a tornado is, draws from a 5 to 15 mile radius, warm, moist air funneling into the updraft, focused into a violent funnel that is pulled to the ground by something called an RFD, a rear-flank-downdraft, a downward surge of cooler, denser (but buoyant) air. The precise mechanism that causes horizontal wind shear to translate into vertical shear in a rapidly rising updraft is still only partially understood - every year we get a little bit closer to unlocking the mysteries of tornadoes. Thanks to breakthroughs like Doppler radar (and SKYWARN spotters on the ground) the average advance warning time has improved from 6 to 12 minutes in the last 20 years. The public is getting more warning, but every year Americans lose their lives, many of them in or near vehicles, mobile homes, injured or even killed by flying debris. Again, the tornado itself won't kill you - it's what is INSIDE the tornado, debris swirling at 80-200 mph, that can cause death and destruction.

Every thunderstorm is, by definition, potentially life-threatening. It's a paradox of sorts: we rely on thunderstorms for much of our summer moisture, without them Minnesota would have a climate similar to that of New Mexico (where they can't grow corn, beans and wheat). But every T-storm contains lightning, which claims more lives in the USA every year than hurricanes and tornadoes COMBINED. The most dangerous time: at the very beginning and the end of a thunderstorm. Just because the rain has stopped doesn't mean the lightning threat has passed. every year a handful of Americans are struck and killed by lightning, blue sky above their heads, a T-storm off on the horizon, 5-15 miles away. The expression "bolt from the blue," or "out of the blue" rings true. The good news? People struck by lightning, even those who appear to be dead (no pulse, no breathing) can usually be revived by employing prompt CPR (no, you will NOT be electrocuted touching the victim). Some 80% of lightning victims can be literally brought back from the dead using CPR, but many will suffer from life-long injuries and disabilities.

Bottom line: you want to avoid unnecessary risk when lightning zigs and zags overhead. A few tips:

1). When you first see the sky blackening, hear the first rumble of thunder or see lightning in the distance, you are theoretically at risk - time to move into a building (or vehicle).

2). Lightning is lazy - it wants the easiest way from the cloud base to the ground. Which means if you're the tallest object in the area you're an easy target. That means avoiding swimming pools, beaches, fishing on a lake (!), golf courses, working in the field, etc.

3). You're generally safe at home, but avoid touching electronic gear when lightning is darting overhead. Using a cell phone is fine, so is watching TV. I would seriously consider disconnecting my PC, Mac or laptop though - avoid the risk of lightning hitting a power line and frying your equipment. Avoid taking showers or baths during electrical storms - it's rare, but there have been reports of people being electrocuted in the bathroom, lightning hitting the plumbing system and traveling into the home. It's rare, a small probability event, but definitely possible. Avoid standing near windows (more for the wind risk - the threat of the window shattering and you becoming a human pin-cushion).

4). Your vehicle is relatively safe during a thunderstorm, again, don't touch the dashboard or electronic equipment if at all possible. You're not grounded in a vehicle - the risk is reduced (but not totally eliminated).

A "Plan B" (Indoor) Saturday? Here's the latest GFS prediction for Saturday morning at 6 am. A storm winding up near Omaha will pump warm, moist air due north into Minnesota, sparking heavy showers, even thunderstorms. It probably won't be a steady rain or all-day wash-out, but plan on a few hours of rain Saturday, temperatures a bit cooler, holding in the 50s (north) and low to mid 60s (south).

As I mentioned in today's print column it's important to have multiple safety nets during severe weather episodes: TV, radio, web, NOAA Weather Radio (still the cheapest form of life insurance), cell phone and e-mail alerts. The more varied sources you have to get the warning, the better the odds you'll get enough warning time to protect your family. Do NOT rely on the emergency sirens: they were never meant to be heard indoors. They are for outdoor use only.

Weekend Soaker? Still too early to have a high degree of confidence about how much rain we'll see this upcoming weekend, but rain is expected from Friday through Tuesday morning of next week. Model runs are contradictory (what's new?) but over 1" of rain seems quite possible from this next system.

An expansive blocking bubble of high pressure temporarily stalled over the Great Lakes will keep us partly to mostly sunny into Thursday, a weak area of showers sliding off just to our south across Iowa tomorrow. The next storm winds up late in the week, spreading a shield of rain across Minnesota Friday, enough warm unstable air may surge north for a few embedded T-storms Friday night and Saturday. The latest guidance suggests this storm will stall over the Great Lakes, and that could prolong periods of rain into Sunday and Monday, showers may not taper until early Tuesday. We get a break around the middle of next week before yet another storm arrives the first weekend of May (May 1-2). The GFS is printing out over 1" (again) that weekend - seems like we're sliding into a wetter, cooler, stormier pattern. The rain is coming in the nick of time. Between heightened allergies and a significant fire risk, and the need for soil moisture for spring planting - I'm hopeful that we'll see the rain we need to put us in good shape for the summer growing season. Fingers (and eyes) crossed.

Volcanic Spectacle. The last time the Icelandic volcano erupted (hundreds of years ago) the eruption lasted 3 months. Click here for 9 strange facts about the volcano, which may take a toll on Europe's economy in the weeks and months to come. Could there be a link between climate change/warming and an uptick in volcanoes worldwide? It may not be as laughable as it sounds at first blush. More melting = less weight, less pressure on the magma deep underground, making it (theoretically) easier for the magma/lava to reach the surface. Click here to read about the X Factor linking climate change and volcanic activity. Far-fetched? Sure. But history teaches us that we ignore these potential links at our own peril.

Icelandic Volcano vs. European Flights. Thought this was interesting: the volcano is injecting about 7,000+ tons of greenhouse gases into the atmosphere daily, vs. over 344,000 tons from planes flying over Europe. Helps to put things into perspective a bit.

Warmer + Drier = Spike in Allergies? Again, it may sound like a stretch, but when you stop to think about the symptoms of warming (drier for much of the planet, more extremes, etc) it makes a certain about of sense that allergy-sufferers might be doing more sneezing and wheezing in the years ahead. Hope the scientists are wrong about this. Click here for an interesting story from the National Wildlife Fund.

Record Ice-Out on Rainy Lake. Thanks to Dave Dempsey at Conservation Minnesota for passing this nugget along - you can read the story here. Ice was off Rainy Lake April 10, April 4 on Lake Katebogama.

U.S. Tornado Trend in 2010. We've seen an unusually low number of tornadoes so far this year, only 79 so far in 2010. But (apparently) that does not let us off the hook for the rest of the year. For the story (blog) from NOAA click here.

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

Today: Partly cloudy, unseasonably mild, very light winds. Winds: NW 3-8. High: 71

Tuesday night: Patchy clouds. Low: 43

Wednesday: More sun, breezy, a bit cooler. High: 66

Thursday: Mix of clouds and sun, still dry. High: near 70

Friday: Cloudy, periods of rain. High: 67

Saturday: Showers, a few heavy thunderstorms possible. High: 65

Sunday: Showery rains linger, a cool, damp breeze. High: 62

Monday: Storm stalls, rain off 'n on. High: near 60

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