Friday, September 3, 2010

Slow Warming Trend (not bad for a holiday weekend!)

Hints of October. I know - yesterday felt like a cold slap across the face (not that I have any idea what THAT feels like). Warm, moist air wrapping all the way around a vigorous Great Lakes storm approached from the NORTH on Friday, keeping central and eastern MN and all of Wisconsin socked in with low, ragged, stratocumulus clouds, leaking a few light showers and sprinkles. Yes, it was partly-nasty out there - but today should be a step in the right direction with more sun and less wind.

June 17 Case Study. Fascinated by tornadoes? On June 17 as many as 45 tornadoes skipped across Minnesota, setting a new one-day record for the most twisters ever observed. Three of those were 1/2 mile-wide EF-4 (Kansas-size) tornadoes. How did this happen - what were the dynamics in place that could have resulted in such an Oklahoma-like outbreak? Click here to read of the best overviews of June 17 I've come across from "Convective Addiction" (great name, by the way).

The Eye That Never Blinks. On Friday the International Space Station flew right over the eye of Hurricane Earl as it buffeted the Outer Banks of North Carolina. Note how the eye was ragged and covered with clouds, not the sharp, well-defined structure that often corresponds with an intensifying storm.

Rainfall Measurements from Space. Yesterday the TRMM weather satellite passed directly over Hurricane Earl, special sensors onboard the low-orbiting satellite capable of estimating rainfall rates 220 miles below - literally Doppler radar pointing straight down. More from NASA here.

Spiral Swirl. No, it's not just your generic, run-of-the-mill storm approaching the eastern seaboard of the USA. Friday hurricane-force winds were still affecting an area roughly the size of Colorado - Cape Cod will be sideswiped by 50-80 mph gusts this morning, before Earl accelerates toward Newfoundland. Satellite image courtesy of NASA's "MODIS" Terra.

Shades of October. 61 for a "high" in the Twin Cities? That's the average high for October 7. Nearly a quarter inch of rain fell from Duluth to Grand Marais, .01" at St. Cloud and a trace of sprinkles in the Twin Cities.

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

Today: Coolest day. Mix of clouds and sun, still windy, cool & comfortable. Winds: NW 10-20. High: 68

Saturday night: Clear and chilly for early September. Frost possible near the Canadian border. Low: 49 (metro). 30s possible north of the Whitefish Chain of Lakes.

Sunday: Nicest day? Plenty of sun, less wind - still low humidity. Winds: E/SE 8-123. High: 75

Labor Day: Dampest day. Clouds increase and thicken - a few showers possible PM hours, maybe a stray T-shower. Winds: SE 10-20. High: 77

Tuesday: Shower early, then rapid clearing, turning breezy and cooler. High: 71

Wednesday: Blue sky early, then clouds increase late. High: 73

Thursday: Mostly cloudy with a few showers, thunder possible. High: 75

Friday: Still damp & unsettled with showers and T-storms likely. High: 77

If it's summer, why is my furnace growling away in the background? Why are we seeing an unusually early outbreak of jackets and sweatshirts (frost in the forecast up north late tonight?) Truth be told "meteorological summer" runs from about June 1 to September 1, marking what is (historically) the 90 warmest days of the year in Minnesota. As far as the atmosphere is concerned autumn really began a few days ago, and that wasn't too hard to believe, going out to retrieve the newspaper this morning. Good grief. Hard to believe it was 94 F last Sunday.

By the way, August was 6.4 degrees F. warmer than average in the Twin Cities with nearly 5" of rain, more than .80" more rain than average for the month. According to Professor Mark Seeley in his weekly WeatherTalk update there were 15 days in August with a dew point greater than 70 in the Twin Cities. Statewide temperatures last month ran 2-7 F warmer than average. Tornadoes reported on the 7th, 12th and 13th of last month.

Yesterday was the definition of "blustery" - it felt like Tropical Storm Bubba was whipping up the Mississippi (by the way, the Great Lakes are way too small, and way too chilly, for hurricane development to take place). A few years ago there was a made-for-TV movie about a hurricane forming over Lake Michigan, pounding Chicago. I almost fell off my sofa laughing - but it's amazing how gullible people can be (especially network executives). Good grief.

Today will be a step in the right direction - more like late September with a stiff northwest breeze (10-20 mph) - not quite as windy as yesterday, with a mix of sunshine and popcorn-cumulus clouds. Highs should hold in the 60s, with some 50-degree highs up north of the Whitefish Chain - we're talking sweatshirt weather much of the day. Winds ease tonight, and if they go to calm we could - in fact - see a premature frost from the Iron Range to the BWCA to Rainey Lake and the International Falls area, coming 1-2 weeks ahead of schedule. Sunday still appears to be the nicest day of the weekend - highs in the low to mid 70s with less wind (blowing from the east/southeast at 8-13 mph). The sun should be out much of the day, but an approaching storm may spread a canopy of mid-level altocumulus and high-level cirrus clouds across the state by afternoon, dimming the sun at times. Not perfect, but pretty nice - par for the course in September with temperatures only a couple degrees cooler than average.

Labor Day? The weather continues to deteriorate, some sun possible during the morning, but clouds on the increase as the day goes on, a pretty good chance of late-PM showers and even a few thundershowers as a storm approaches from Nebraska. It will NOT be an all-day rain-out, and you'll probably be ok during the morning hours, but all bets are off after the lunch hour. Monday still looks like the mildest day, highs in the mid to upper 70s with a stiff southeast breeze.

A cool frontal passage kicks up a few showers/storms Monday night into early Tuesday, but skies should quickly clear Tuesday morning, fair skies the rule from Tuesday afternoon into midday Wednesday. The next frontal boundary shoves showers back into town next Thursday/Friday (some locally heavy rain can't be ruled out). It's early to be pontificating about the following weekend (Sept. 11-12) but Saturday may be gray and mostly cloudy with residual moisture keeping us socked in (but probably no significant rain). If I had to wager a small bet I'd predict Sunday, the 12th, as the sunnier, nicer day.

I wouldn't read too much into this latest cold front. It does NOT mean an early winter, or a harsher-than-normal winter is imminent. Chalk this up to random variability (and losing over 2 hours of daylight since June 21). It was the first real puff of autumn, but there's plenty of lukewarm, shirtsleeve weather left this month. Right now I don't see any 80s imminent, but count on lot's of 70s, and I am fairly positive we'll enjoy at least 3-6 more 80+ days in the weeks to come. Don't write summer off just yet...

September Averages. Looking for average temperature/rainfall/snowfall data for a specific month here in Minnesota? I didn't think so - but hypothetically, if you WERE looking for that kind of information you could hit the weather-geek-jackpot by clicking here. Go for it. Maps & data courtesy.

Precipitation Rainfall. I found this vaguely interesting - eastern MN routinely picks up TWICE as much rainfall as western Minnesota. The Twin Cities metro area routinely picks up 3 to 3.5" of rain.

Earl Rainfall Totals. NWS Doppler radar estimates shows some 2-5" rainfall amounts from Earl's spiral bands of moisture wrapping around the eye. Earl is accelerating to the north/northeast, which is cutting down on the rainfall totals (a slow-moving hurricane can easily dump out 10-20" of rain on a given community).

Global Hawk. Yes, unmanned drones are good for things other than chasing terrorists in Afghanistan. NASA is using a high-altitude (joy-stick controlled) aircraft (minus a human pilot) to fly high above hurricanes, scanning the storms below to get a 3-D slick of temperature, winds and moisture fields, trying to get a better grasp of how these storms are powered and why some strengthen dramatically, while most fizzle. This is part of the "GRIP" program that runs through September 30 - more on this cutting edge research here (scroll down a little). Click here to see a near real-time image, the latest flight reconnaissance from the Global Hawk.

"GRIP" Satellite Overview from JPL. Click here to see a composite image of the latest experimental imagery from GRIP, showing Earl swirling off the Carolina coast. Things are definitely heating up in the tropics, a sudden spike in hurricane activity, but through the end of next week steering currents should nudge any hurricanes away from the east coast of the USA.

Hurricane Tips (from the Onion). My favorite is the last tip: "to minimize risk of hurricane damage, avoid building vacation home atop ocean." Makes sense to me. O.K. It's a little naughty but you would expect nothing less from The Onion.

Major Quake. Saturday morning (local time) a major 7.4 quake struck New Zealand, resulting in very significant damage in Christchurch and surrounding areas. Since the epicenter of the tremor was over land, no tsunami warning was issued for the surrounding waters of the South Pacific. The New York Times has a summer here.

Mission To The Sun. Don't worry we'll go at night. Trust me - this will all work out. When I first saw this headline I had to do a triple-take. Say what? By 2018 NASA is planning a flight to within 5 million miles of the sun's atmosphere to try and answer a few vexing questions: why is the sun's outer atmosphere hotter than the surface? And what is the mechanism that propels the "solar wind" through the atmosphere? I know both questions will probably keep you up tonight. Sorry. For more on the planned sun-expedition, click this NASA link.

How Can Los Angeles Adapt To Coming Climate Change? Scientific American has a very interesting story about how L.A. (and other major cities in the southwest) may adapt to a drier climate in the decades ahead. We tend to focus all our attention on oil - when it turns out that the most precious natural resource of the 21st century may wind up being water.

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