US January 2019 Outlook

Written by on December 25, 2018 in United States of America with 0 Comments

After a cold October and November for much of the Lower 48, December started off on a similarly cold note with the aid of a retrograding blocking high from the Canadian Archipelago to Alaska.

However, as you can see from the below 30 day animation, around the 10th saw a 360 flip with ridge replaced by trough over Alaska and this open the door for Pacific air to flood the country.

As a result of this change, December as expected has turned out mild, especially so in the areas which were coldest during the autumn.

Credit: Michael Ventrice

No surprise that we had a predominantly positive AO/NAO which drove the mild month.

However as we head for 2019 there is a big shift coming in the not so distant future. The reason? We have an ongoing SSWE.

The models have been showing for a solid few weeks now that a potential split in the vortex may occur with one piece diving into Canada and the other Europe.

The potential cause of this SSWE could be linked to the MJO and increased convection over the Indian Ocean which drives heat from troposphere into the stratosphere. This also supports a mild US pattern which we’ve seen in the last couple of weeks. However, as the MJO continues to track east and the SSWE continues, we’re heading for a big shift from December into January.

Credit: Judah Cohen

Check out the CFSv2 10mb temp anomaly for the month of January.

Credit: Judah Cohen

Notice in the below charts that the Indian Ocean clears of thunderstorms and this focuses over Indonesia currently and into early January, the west Pacific. This supports a colder pattern and combined with SSWE, a much colder pattern.

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

No surprise that we’re going to the below 500mb scenario through January… The building of heights over the Arctic but most importantly over Alaska and Greenland with a trough over the Eastern US.

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

An active southern branch jet stream could bring not only frequent outbreaks of cold but major snow events too, especially up the East Coast.

Just how cold could it get and when.

I’d be looking for an increasingly colder pattern to start developing southwards over the continent quickly after the New Year and by weeks 2, 3 and 4, some major outbreaks of arctic air could be punishing much of the nation given the SSWE and it’s timing in the heart of the winter within a low solar, modoki El Nino year.

This is the setup which could support an outbreak which drives the temp into the -20s for Minneapolis, -10s for Chicago, Cleveland, Detroit, 0 for NYC and possibly down to Nashville, 5 in Atlanta and 10 in Tallahassee. Watch this space.

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