Monday, November 19, 2012

Some talk about winter weather

I've noticed over the past few days that there is increasing talk on weather bulletin boards about the first arrival of really cold air into the Southeast.

The Global (GFS) computer model has been playing around with a scenario in which strong high pressure forms next week over southern Alaska, while a deep low pressure system develops in eastern Canada. If the two systems connect, that is the recipe for a surge of arctic air into the Southeast.

Add a low pressure system from the Gulf of Mexico, and you've got wintry precipitation in our region.

The odds favor this not happening -- not in early December.

The European model, for example, predicts the cold air will move into the Rockies. There's also a chance that the cold air remains trapped in Canada. That is the most likely scenario of the first few days of December, with Carolinas temperatures remaining around average for this time of year.

But for the first time this season, there's at least a wintry look for the eastern United States on some of the computer models.

There has been a significant change in the winter outlook across the country. Originally, meteorologists expected a weak El Nino condition, which would bring wet and chilly weather to much of the South. But now the forecast is for a neutral El Nino-La Nina situation.

That makes the North Atlantic Oscillation an important player in our weather. The NAO has been negative recently, which means weather systems have been dropping from Canada into the Southeast, then curving eastward to the Atlantic Coast, and then sweeping up the coast. That was the track of Hurricane Sandy, and it's been the same path for a couple other recent storm systems.

If that situation continues, the Carolinas will be near the "battle ground" between mild and cold air -- and in the path of storm systems. And that is a recipe for "close-call" winter storm systems, the kind that can bring sleet and freezing rain.

It's a lot of speculation now, but we should have a better idea of the pattern -- at least for early-winter -- fairly soon.


Anonymous said...

Well its not too bad right now.-1F Clear but windy. If the winds drop off it will drop to -30F or so. Typicall November in Fairbanks Alaska. Warmer than last winter when it was -40F this time of year....