With blocking now showing up over the arctic and extending down over Greenland, the stage is set for a cold or very cold January across the Lower 48. Up till now, the main driver of what has been a cold December, has been the Eastern and Western Pacific Oscillation (WPO and EPO) with no guidance from the NAO or AO. The cold has been all the more impressive across the US given that the AO (arctic oscillation) has been firmly positive with a strong polar vortex centred directly over the pole.
One significant feature we tend to look at during the winter months for longer term guidance is stratospheric temperature across the pole. Up till now, the polar vortex has been strong over the pole.
Here’s the initial.
By 240 hrs, note the strong warming over Siberia at 10mb which is distorting the vortex, stretching it out. That tends to force arctic air south into the United States as well as Europe when you’ve that kinda of warming on the Asia side of the pole.
Now that we’re entering true winter, the hand off is now shifting from Pacific to Arctic and Atlantic signals and yes, there is no doubt that January will support a cold pattern compared to last year. Keep in mind that January was largely warm from the Plains on east while it was cold in the West, opposite to what we’ll see this year.
This morning was the coldest yet for the Dakotas. It plummeted to -38 at Glen Ullin, ND.
- Source: weather.com
As for tonight, well it’s frigid from International Falls where it’s already down to -28 to Des Moines at 1 and Chicago at 2. By dawn Christmas Eve, it will be considerably colder. This has been the trend this season, with well below normal temps compared to this time last year. Amazingly Chicago is running a solid 15 degrees colder than last December and tonight will bag a 3rd subzero night.
Following the incredible warmth up the East Coast yesterday with 81 at Norfolk, VA and 71 at New York, it’s a cold Christmas coming up for the Northeast with many likely to not even reach freezing, what a drop in just 48 hrs.
Here’s the turnaround between Sunday and Tuesday. Check out the Appalachians.
- Source: AccuWeather
FRIGID NEW YEAR
The pattern keeps the shots of arctic air coming south into the N Plains and Great Lakes with another significant push in the run up to New Year and into the first few days of January. Like we’ve been seeing, any mild surge is weak and very short lived.
Check out these 850 temps off the ECMWF control.
- Courtesy/Owned by AccuWeather Pro
Here’s the cold signals you want to see with the NAO, AO and PNA.
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As you can see, the CFSv2 shows the strong warming over the pole with hooking up of the ridges between Alaska, Greenland and east Europe which forces the arctic reservoir south into the US and Europe and likely trapping it there..
Week 1-2
Week 3-4
And so the temperature trend goes down down down from Jan 1-15.
Week 1-2 temps
Week 3-4
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