© 2019 Terry Swails

HAPPY TURKEY DAY! SIGNS OF WINTER...

November 23, 2017

Yesterday we looked at how the remainder of November and the beginning of December looked dry and on the mild side. Today, we'll explore why I'm bullish on a change to what I believe will be a more wintry pattern around the 8th-11th of December, Granted, I had expected this closer to Thanksgiving but as the saying goes, better late than never.

 

To support my point I'm going to turn to the output of the GEFS and and EURO EPS ensembles. In the  teleconnections I'm about to show, you can see the forecasts of each model and the temperature analogs they correlate to during the month of December.

 

First the EPO (Eastern Pacific Oscillation)

 

Both the EPS and GEFS have the EPO negative against the base going into December 8th. A negative phase in December correlates to significantly below normal temperatures in December.

Now the NAO (North Atlantic Oscillation) 

Both the EPS and GEFS have a significantly negative phase of the NAO going into December 8th. That translates to widespread cold over the Midwest.

Now the AO (Arctic Oscillation)

Both the EPS and GEFS show the AO going strongly negative by December 8th. The negative AO in December yields another cold scenario, much like the negative phase of the NAO.

Two other teleconnections, the WPO (Western Pacific Oscillation) and PNA (Pacific North America) both are neutral approaching December 8th which implies near normal temperatures. So the -EPO, -NAO, and -AO should be the dominate drivers  going into the second week of December. As you can see, that very much points to the development of a cold pattern around that time. 

 

The other big driver to watch is the MJO (Madden Julien Oscillation)). Into early December it will be traveling through the warm phases of 4, 5, and 6. That's why the next 2 weeks stand a high chance of being mild overall. You can see the progression by following the dotted green line. It ends in phase 6 December 6th.

After December 6th, there is a good chance the MJO will transition into Phase 7, a cold phase for the Midwest. You can see it making the bend and heading in that direction. You can also see in the above graphic what temperatures in phase 7 look like in December.

 

If the progression continues to go the way of the cold MJO phases of 8, and 1, (not a certainty yet) we could find ourselves in some legitimate cold. The 18z GFS operational run shows the potential day 16.

To get snow, you absolutely need to have the cold. This would be the first step in that direction. You can also see below that phases 8 and 1 are wetter (stormier), especially 1. That could be a signal that the pattern would become more active and perhaps snowier. 

Phase 8

Phase 1

In the meantime, we enjoy what will be a fantastic period of holiday weather. Dry conditions will be with us through the weekend and you travelers will have no weather worries. In fact, you Black Friday shoppers won't even need the coat Friday afternoon when temperatures in my area my reach record breaking levels in the low 60s. The latest GFS shows this for highs Friday afternoon.

Before I sign off, I just wanted to wish each and every one of you a happy Thanksgiving. I sincerely hope you have as much to be thankful for as me. If I could just get a snowstorm life would be a dream! Roll weather and go easy on the gravy! TS...

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