Updraft: December 1, 2009 Archive

December 1st: One more mild day

Posted at 8:34 AM on December 1, 2009 by Paul Huttner (1 Comments)

NWS wind chill chart. We will reacquaint ourselves later this week.

Call it a cameo. Indian Summer lite. One last day to stroll aimlessly and enjoy the balmy 40s to open December.

Meteorological winter starts today, and the weather will catch up with the calendar starting tomorrow. As if on cue, the season's strongest cold front will ooze colder air into Minnesota Wednesday.

Meteorological winter begins after the wild roller coaster weather ride that was meteorological fall. The Twin Cities' fall temperature numbers are remarkable.

September: +5.5 degrees (11th warmest)
October: -5.5 degrees (4th coolest)
November: +10.2 degrees (2nd warmest)

Top 5 Warmest Novembers
Minneapolis
Average Temperature (°F)

Rank/Value/Year
1. 46.4° 2001
2. 42.7° 2009
3. 41.8° 1999
4. 41.2° 1899
5. 40.3° 1931

Period of Record: 1871-Present

It is remarkable that November's average temperature of 42.1° was nearly warmer than October's average temperature of 43.2°. The Twin Cities NWS has a great wrap of November's wacky temperature pattern.

Get ready for a chilly slap in the face this week. NOAA's North American surface analysis shows sub-zero air pooled up in the Yukon Territory ready to move south. The air mass will modify some as it moves south, but we could see our first sub-zero overnight lows in northern Minnesota this week. It looks like we'll have to settle for lows in the teens in the Twin Cities.

The colder weather pattern looks as if it will last a while. Temperatures may be colder than average in much of the Midwest for at least the first 10 days of December. Some moderation is possible as we approach mid-month.

PH

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Pattern Change: Here comes winter

Posted at 4:21 PM on December 1, 2009 by Paul Huttner (1 Comments)

Latest NOAA 30-day outlook for December favors colder than average temperatures over much of the USA.

It appears our on again, off again seasons are about to turn on again. In a big way.

The latest series of medium range forecast models are screaming winter for the Midwest. The so called "polar front" jet stream is about to buckle, and send wave after wave of frigid air into the nation's midsection. At this time it appears the pattern may last right into mid-December.

NOAA GFS model 500 millibar (18,000 feet) chart shows deep trough over the central U.S. Friday. This upper air pattern can drive cold air all the way down to the Gulf of Mexico.

The colder than average pattern would be a departure for moderate strength El Nino events in Minnesota. There is about a 71% correlation between milder than average winters in Minnesota during moderate strength (Tropical Pacific SST's +1.2 to +1.8 degrees) El Nino years.

In a recent look at moderate strength El Nino years since 1950, the Twin Cities NWS found that every December has been milder than average in those events. If it happens, this would be the first cooler than average December in a moderate El Nino year.

The cold blast this week should be enough to begin to freeze up open water in ponds and small bays this week in area lakes. Safe skating and ice fishing is likely at least two or three weeks away though. The average date of initial soil freeze in the Twin Cities is December 8th. The coming cold wave and lack of insulating snow cover may put us right on schedule this year.

Hopefully your outdoor holiday light display is all done by now!

PH

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