If models prove correct with late month SSWE, a 1979 or 2010 style January-February is on the table!
The latest GFS ensemble continues to show an end of the month SSWE which could make for a very interesting January ahead. There’s still plenty of room of disappointment but our chances for cold is increasing.
Note the temperature difference at 10mb over the Arctic between now and January 1st.
Credit: Tropical Tidbits
Credit: Tropical Tidbits
Rapid warming throughout the depth of the polar stratosphere expected for the remainder of this month, significantly weakening the polar vortex. GFS, CFS and CMC ensemble means are currently simulating a strong SSW event, with an impressive 20m/s easterly component at 10hPa. pic.twitter.com/aklMOXrqH3
— James Warner (@MetmanJames) December 16, 2018
The amplified MJO is not to be forgotten about and could also help with the cold blocky pattern down the road.
A statistical model that I've developed using the observed state and amplitude of the MJO shows an evolution towards high latitude blocking from the North Pacific through the North Atlantic in 4-6 wks. Sets up a cold pattern for N America and Europe. We'll see how this plays out pic.twitter.com/C1Rvr9vRK3
— Michael Ventrice (@MJVentrice) December 14, 2018
Late December SSWE’s are textbook in timing as it drives the coldest air south at climatologically the coldest time of year.
Therefore, in theory this could have the potential at delivering a 1979 or 2010 style January-February and even March period for the UK.
ECM seasonal model update of Dec 2018 for Jan-Mar 2019 reminds me a lot of Winter 1946-47. pic.twitter.com/a80RIXN8f0
— Snowbie (@SnowbieWx) December 10, 2018
New Analogue year for Jan 2019
JAN 1977 pic.twitter.com/Yt4g067rPB— Amir Mohsen Z (@AZohouria) December 15, 2018
As pointed out in my winter forecast. In a low solar, modoki El Nino year an SSWE could support a major period of cold, a 20-40 day spell of severe winter conditions on both sides of the Atlantic with classic Greenland block in between. This much expected mild December could well fool many and has been known to be followed by bitter second halves to winter.
In fact in my forecast I also stated that winter may not kick in proper until mid January and given the usual delayed response from initial SSWE at 10mb down into the troposphere, it usually takes about 10-15 days after the initial 70C warming within 5 days for the full effects to be reached at or below 500mb. That would take us into January’s 2nd week.
Some of a great cold spells of the last 100 years followed fairly benign if not warm Decembers.
There has been some encouraging signs for us cold weather weenies of late. The lack of strength in the Atlantic stream and indeed the warming waters surrounding Greenland.
Credit: Tropical Tidbits
Both a weaker winter jet and warm waters surrounding Greenland help the development of a Greenland blocking high.
Here’s the latest CFSv2 500mb height anomaly for January. Classic!
Credit: Tropical Tidbits
I must stress however that despite the increased chance for a late month SSWE which the timing couldn’t be much better for maximum cold, there’s no guarantee that the blocking and cold pools will sit perfectly for us. As usual, time will tell.
This change will be welcome from for Tennessee and Eastern North America. Right now it is extraordinarily warm for us and doesn’t feel like pre-Christmas weather at all. Hopefully we will return to seasonable weather soon.