Monday, July 5, 2010

Getting Better (recap of Monday's bizarre weather)

Better Than Water-Skiing Squirrels. No, this has nothing to do with the weather - consider it blog-filler, but definitely one of the cutest images I've stumbled upon in recent days.

What a Monday. I'm exhausted, slumped over the Doppler, still scratching my head in wonder over one of the strangest meteorological phenomena I've ever tracked here in the great state of Minnesota.

Let me get this straight: sunshine in the morning, one round of heavy showers/downpours drifting from SOUTHEAST TO NORTHWEST around mid afternoon, a rare situation known as "retrograding" - when weather systems stall very odd things can result. That line stalls, then does a U-Turn and tracks from WEST TO EAST during the late evening hours, producing more gulley-gushing rains, 1-2" of rain in less than 2 hours in some towns. This was a truly a tropical airmass, twice as much water in the air as typical on the 5th day of July. The same front that pushed through Saturday night, stalling just south and east of Minnesota, lifted north Monday afternoon, a twist of unusually cold air aloft - counterclockwise winds pushing a line of instability showers in a very unlikely direction. Just when you think you've seen everything - along comes the 5th of July.

Gust Front. Look carefully and you can see a thin, curvy line of precipitation out in front of the main cluster of T-storms (moving from southeast to northwest), a "gust front", a miniature cool front created by rain/hail-cooled air reaching the ground, spreading out ahead of the main band of showers and storms.

* In addition to downpours and local street flooding there were a few reports of "cold air funnels" Monday afternoon, the atmosphere unstable enough for funnel clouds - no evidence any of them ever reached the ground, but another weather oddity, considering the atmosphere was not ripe for traditional tornadoes. Every time I turn around this summer there's another weather-fluke.

Manic Monday. Sunny start, PM storms, assorted cold air funnels, flash flooding, weather systems moving east to west (3 pm), then west to east (7-11 pm). Just business as usual here in the Land of 10,000 Weather Extremes. No rain in Alexandria, but a downpour unleashed .76" rain on St. Cloud. Up until 7 pm Crystal (northwest suburb of Minneapolis) saw only .03" of rain, while Flying Cloud Airport in Eden Prairie (southwest suburb) saw .79" of rain, .76" in downtown St. Cloud, but only .33" at the airport. Keep in mind this was before the second round of storms that tracked from west to east during the late evening hours. Flood advisories has to be issued for much of the metro area - but conditions should (rapidly) improve during the day Tuesday. Talk about a complicated pattern...

File: Cold Air Funnels. When the atmosphere is unusually unstable - extremely cold aloft, relatively warm and moist near the ground - resulting updrafts can spin up brief funnels (even if wind shear isn't present, usually a prerequisite for large, violent tornadoes). Cold air funnels rarely reach the ground - when they do winds can exceed 60-80 mph, producing minor damage.

No more retrograding systems, no more weather oddities, now that a more traditional west to east wind pattern has returned, pushing last night's clusters of T-storms into Wisconsin, resulting in more sun today, and only a minimal chance of an isolated, late-day T-shower (affecting less than 5 or 10% of the state).

We get a break today, a chance to dry out for all of 24 hours, before the next front rumbles into Minnesota late Wednesday and Wednesday night. A bubble of high pressure dries up our puddles, the sun stays out most of Thursday, Friday, and a good portion of Saturday as well. It's early to be making hand-waving proclamations and predictions about the weekend weather details, but based on the data I'm looking at right now Saturday appears to be the sunnier, drier, nicer day to loiter by the lake - the next system arrives with more showers/storms Saturday night and Sunday.

Partly Sunny - Partly Thundery. This high-resolution NASA "Terra" 250 meter image was snapped by a low-orbiting satellite midday Monday - the northwestern half of Minnesota still enjoying a beautiful, sunny sky - while T-storms were starting to sprout south/east of the Twin Cities, tracking from SOUTHEAST TO NORTHWEST! Click here to see today's "MODIS" image of the USA, click on Minnesota to zoom in. Only on a holiday...

Look at the bright side: we salvaged 2 1/2 out of 3 days, coming on the biggest holiday weekend of summer. A hot, windy, sunburnt Saturday, a mostly-grey, ominous 4th of July (but mercifully dry statewide), and a very pleasant Monday morning. Granted, the weather went (quickly) downhill Monday afternoon as that (bizarre) pattern unfolded: weather systems stalling, backing up, before resuming to normal. Whatever normal is. It has not been a normal summer, but I'm still counting my blessings, atmospheric and otherwise.

Triple Digit Heat. Be glad you're not stuck out east today - what a sizzling, antiperspirant mess, highs forecast to top 100 from Washington (101 F) to Baltimore (102 F) to 100 in Philadelphia to 101 in New York City. Just like a big snowstorm in January doesn't disprove climate change, a heat wave out east in the summer doesn't prove global warming, either. This is "weather", not "climate".

Record-Breaking Heat? Residents all up and down the east coast are coming up with creative ways to try and keep their cool. Click here for a good summary of the building heatwave gripping much of the east, impacting as many as 100 million Americans. The worst of the heat should ease within a couple of days, peaking today and Wednesday.

Bonnie? According to NHC there is now a 30% probability that an area of disturbed, thundery weather moving into the Yucatan Peninsula will strengthen into a tropical storm (down from 50% Monday). The storm is taking a track almost identical to "Alex", steering well south of the oil in the Gulf of Mexico.

Exhibit A. That's me, on my first attempt to "knee-board" on Lake Minnetonka. It took a few tries but I finally figured it out (arms still aching - what an upper-body workout). My kids make it look easy - the old man had to at least try to keep up and save face. Minutes later I did a face-plant, took me 5 minutes to pick all the milfoil out of my teeth. This was late morning Monday, before the storms arrived (from the southeast) - something that happens maybe once or twice a year.

Paul's SC Times Outlook for St. Cloud and all of central Minnesota

Today: Partly sunny - isolated T-shower possible, but most of the state will remain dry. Winds: E 5-10. high: 83

Tuesday night: Partly cloudy and pleasant. Low: 64

Wednesday: Sunny start, good chance of T-storms PM and nighttime hours Wednesday. High: 80

Thursday: Plenty of sun, a rare dry day. High: 81

Friday: Mostly sunny and beautiful. High: 82

Saturday: Probably the nicer day of the weekend - hazy sun, sticky - a few storms possible far western MN by nightfall. High: 82

Sunday: Unsettled, more clouds with more numerous showers and T-storms. High: 79

Monday: Some sun, a few more showers/storms. High: 81

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