Saturday Morning Long Range Discussion: Evidence building on big mid month cold outbreak

Back on post on november 19th I discussed how the uptick in warming in the stratosphere was going to influence our weather pattern by the time the 2nd week of December rolled around. Since then, the stratosphere has continued to warm and it now will have effects on our December weather. Lets take a look at 50mb temperatures over the last month. This is basically mid way up in the stratosphere. You can clearly see the warming taking place up in the north Pacific into the Arctic..

This has resulted in stress to the polar vortex and you can see evidence of a vortex split below at 50mb as seen by the two circles..

This should lead to very cold air if not another impressive arctic outbreak by the 2nd week of December. The models are really struggling with this, but some are starting to catch on. Below is the gfs ensemble forecast for December 8th,,

I pointed out a few key areas here. The trough south of Aleutian islands of Alaska is huge as that normally is the key to pumping up a massive ridge over the west coast into Canada and finally a big trough over the eastern part of the country. We saw this happen with our mid-late November arctic outbreak and I expect this pattern to continue throughout the winter. All due to stratospheric warming which is the result of many of the factors I discussed in my Winter Outlook 2015. 

So enjoy the moderation in temperatures this week. Things could get quite nasty down the pipeline with bitter cold temperatures and frequent shots at snow.

More on Monday.