© 2019 Terry Swails

ON THE ROAD TO WINTER....

October 31, 2017

I told you the cold was coming 2 weeks ago when it was apparent a typhoon was passing east of Japan and the MJO was headed to the cold phases 7, 8, and 1. Bam...right on schedule! The chill hit last weekend and now a reinforcing blast will bring us the coldest Halloween in at least 10 years, in some spots going back to 1996.

 

Here's the temperature departures for the past 7 days. Were it not for a couple really warm days at the beginning of the period this would be far more dramatic than it is.

You can compare the recent change with the rest of October below.

The next 2 weeks it looks as though there will be a period of give and take where the northwest flow relaxes and the pattern recharges. In general temperatures will remain below normal but not as cold as the past 5 days. Here's the day 5-15 temperature departures off the CFSv2.

The overall appearance of the above temperature departure is interesting to me because it's remarkably similar to what you would expect in a La Nina winter. which seems to be coming on as expected. The climate models are closely clustered showing the trend towards a weak to perhaps moderate La Nina through winter.

Notice the propensity for colder than normal temperature from Alaska to the Upper Midwest like the 5-15 departure is showing. This could be a preview of the upcoming winter. Odds certainly favor it.

Here's another perspective showing the predictable La Nina ridge off the west coast and a polar jet delivering cold to the northern U.S. Snow falls to the north of the jet.

There is a statistical La Nina correlation that shows winter snowfall anomalies higher by nearly a foot in the upper Midwest. Central and southern areas show near to slightly above normal amounts.

The GEFS means are pointing the way with 16 day snowfall totals that look like this.

My area remains south of the snow belt through that period but the building snow pack seeds the air masses where it accumulates. That makes them colder and allows penetration further southeast with time. Eventually, that brings the snow into my area and the central Midwest. The new EURO weeklies are showing that potential. Look at the heavy snow accumulations the control run spits out across the Midwest the next 46 days...ending December 15th

I do not pay attention to the amounts or heaviest bands at this distance, what I do respect is the general trend of a snowy start to winter...very heartening if you are a fan of snow.

 

Anyway, now that October is in the rear view mirror it's time to start getting serious about winter. I'm hoping snow will be on the ground in my area no later than Thanksgiving. Roll weather...TS P.S. Happy Halloween!

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