Wednesday, July 15, 2009

A Year Without a Summer?

Spicer tornado photo taken at 6:40 pm Tuesday evening by professional storm chaser Tadd Parris, who took multiple photos as he raced across Kandiyohi County, trying to keep up with a fast-moving "supercell" thunderstorm. Strong rotation within the storm resulted in a "wall cloud" slowly lowering to the ground, and near Spicer the tornado touched down, resulting in considerable damage. Thanks to Tadd for making this available to WeatherNation and its clients. For some amazing YouTube footage of the tornado on the ground click here, and scroll down near the bottom of the page. Trust me, it's worth your time to check this out.

This is the same cluster of severe, rotating thunderstorms that drifted over St. Cloud, sparking numerous reports of funnels and wall clouds, along with 1-2" rains and a few reports of ping pong size hail. In all there were 4 tornado reports in Minnesota Tuesday, another 4 reports of violent straight-line winds, and at least 16 separate outbreaks of severe hail, greater than 1" in diameter. Looks like that's our excitement for the week.

Wednesday Almanac High: 73, Low: 61, Precipitation: .09"


Today's weather headline may be a bit of a stretch, a slight exaggeration, a bit of cheap, promotional hype leftover from my angst-ridden TV days. Sorry, bad habits die slow. But tomorrow, standing outside your house, being buffeted by a raw, gusty northwest wind, a dull-gray oatmeal sky draped overhead spitting sprinkles, temperatures stuck in the 50s and 60s, you may find yourself wondering (out loud) what the heck is going on? This is NOT the July we were daydreaming about just a few short months ago. This is our reward for surviving a grim, numbing winter? Not fair, I sympathize. Many feel cheated, short-changed, a little bit of atmospheric bait and switch going on. Historically the last 2 weeks of July are the warmest of the year. Not this year.

WRF/NMM Temperature Prediction for 7 am today. Note the 40s over most of northern Minnesota, even some 30s predicted for Lake Superior. These aren't wind chill readings, but surface temperatures!

By now you know that the weather map east of the Rockies resembles something out of mid September, not mid July. The jet stream has been dislodged, pushed several hundred miles farther south than usual for mid summer, dragging unusually cool Canadian air southward into the United States. Cool fronts that should be fizzling out near Duluth and Grand Forks are surviving all the way to Little Rock and Atlanta, which is quite remarkable for July! Why is this happening? Lot's of (hand-waving) theories, but it's awfully tough proving cause and effect when it comes to day to day weather. It may be a symptom of a brewing El Nino in the Pacific. It may have something to do with recent volcanic eruptions from Alaska to Russia - ash injected into the stratosphere can spread out into a thin, hazy cloud 30-50 miles above the ground, dimming the sunlight reaching the ground, temporarily cooling temperatures worldwide. Maybe it's a well-publicized lack of sunspots on the sun, one of the quietest periods on the surface of the sun since the 1920s, from what I've read. The honest answer: we're not sure, at least not yet.

The sun will be out for a time this morning but clouds will quickly increase (from north to south) and temperatures will be cooler than yesterday, a gusty northwest wind means only the brave and foolish will take a quick dip in the lake later today. An unusually strong storm over Ontario Province, Canada is in a holding-pattern, moisture forecast to wrap all the way around this area of low pressure, approaching from the NORTH by Friday. That could mean light showers north of Brainerd and Mille Lacs, with a few sprinkles into St. Cloud and the Twin Cities, dribbling out of a lumpy-looking sky straight out of early October. Talk about free air conditioning. Temperatures won't climb out of the 50s over northern Minnesota today and tomorrow; if skies were to magically clear up north I'd be predicting a rare July FROST up on the Iron Range, near Tower and Embarrass! Clouds will probably linger the next couple of nights, preventing a widespread frost, btw. Yes, you may get some mileage out of that favorite fall sweater, sweatshirt or jacket over the next 48 hours.

WRF/NMM Model Output for 7 pm this evening, showing predicted rainfall between 1 pm and 7 pm today. The models are hinting at a little, light, showery rain, mainly north of Grand Rapids and Bemidji, but a few sprinkles may reach as far south as St. Cloud, even the Twin Cities.

WRF/NMM Temperature Prediction for 1 pm Saturday. Don't panic! Deep breaths. A bubble of high pressure over Sioux Falls, South Dakota will keep our winds blowing from the northwest into Saturday, but temperatures aloft begin to warm, and some of this milder air makes it's way down to the ground, mellowing the mercury into the 70s statewide. Saturday will be the cooler day of the weekend, but with less wind and bright sun it should be a good day for the lake or pool.

Winds are forecast to turn to the southwest Sunday, luring temperatures into the mid 80s, making it the better day to loiter on the beach - by Sunday it will finally feel like summer again. The sun should be out right through Monday, with little chance of significant rain for the next 5 days. The next opportunity for showers and thunderstorms across the state will come next Tuesday as a slow-moving cool front approaches from the Dakotas.

WRF/NMM Output for 1 pm next Tuesday, July 21. A weak cool front will shove a narrow band of showers and storms across the state, with some .25"+ rainfall amounts possible, probably no heavy downpours like we had Tuesday night.

By all means don't write summer off (completely) just yet. The atmosphere has an uncanny ability to balance things out. A few weeks of unusually cool weather is often followed by a few weeks of unusually warm weather as the atmosphere trends toward a state of equilibrium. Highs should be in the 80s most of next week, in fact the long-range GFS model is predicting a string of 90s at the very end of July, possibly 3-5 days in a row above 90. That's way out on a limb, but I have NO doubt that we'll have plenty of opportunity to sweat it out as we end July and sail into August.

July Temperature Outlook from CPC. The Climate Prediction Center is forecasting cooler than average weather from the Dakotas and Minnesota east to the Great Lakes and New England, a result of a southward shift in the jet stream pushing unusually cool south of the Canadian border. Because of the unusually cool start to the month, this forecast doesn't look like much of a stretch, even if we do see a few 90s at the end of July. But I wouldn't be surprised to see a warmer than average August. Place your bets.

Paul's Outlook

Today: Any sun gives way to increasing clouds, windy, still cool. Late-day sprinkles possible. Showery rains far north. Winds: NW 15-30. High: 69

Tonight: Patchy clouds, a whiff of windchill. Low: 51

Tomorrow: Mostly cloudy, hints of autumn in the air. High: 63

Saturday: A mix of clouds and sun, less wind, a bit milder. High: 73

Sunday: More like summer! Bright sun, warming up. High: 83

Monday: Warm sun, more humid. High: 85

Tuesday: Showers and thunderstorms likely. High: 81

Wednesday: Damp start, then partly sunny and drier. High: near 80

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