My December Thoughts

[donsutherland1]

The combination climatology associated with moderate/strong La Niña events, the development of a negative PDO (-1.45 in October), a composite of three analogs (1953, 1954, and 1998) that has doen well to highlight the location of warm-cold anomalies since August, and, to some extent, the CFS Model's monthly idea for December leads me to believe that much of the USA will feature milder than normal readings for December as a whole.

There could be a few colder outbreaks, especially in the first half of December. In fact, both the CFS and experience with Winter 1949-50 suggest the potential for a larger area to wind up cooler than normal than I have depicted. The area in question encompasses northern Idaho, Montana, North Dakota, and South Dakota. Given the observed warming in recent decades, I've leaned toward the milder outlook in that region given some of the conflicting signals.

[donsutherland1]

The Climate Prediction Center's (CPC's) December outlook is now out. CPC's forecast follows:

[PTPatrick]

Would this be sign that CPC expects a mean trough over the west for December? Any guesses as to the storm tracks? Denver seems to be in the in between area for most of the forecasts a look at...most say average to slight above average temps...but average precip. We have been low on snow so far and quite warm over all...but we could make up our snow deficit with just next weeks storm...and there are 2 weeks left in november.

[donsutherland1]

PTPatrick,

The CPC outlook might indicate a trough near the Pacific Northwest or perhaps centered over the Gulf of Alaska. CPC didn't mention trough-ridge positions in its discussion.

As for precipitation, CPC stated:

PRECIPITATION TENDS TO BE LIGHT OVER MUCH OF THE SOUTHERN PART OF THE COUNTRY IN LA NINA WINTERS, SO THE CHANCES OF BELOW MEDIAN PRECIPITATION IN DECEMBER IS ENHANCED IN THE SOUTHERN PART OF THE CONUS FROM SOUTHERN CALIFORNIA THROUGH TO THE EAST COAST, EXTENDING NORTHWARD ALONG THE EASTERN SEABOARD TO SOUTHERN NEW ENGLAND. THIS SIGNAL IS SUPPORTED BY A BROAD RANGE OF TOOLS INCLUDING DYNAMIC MODEL FORECASTS FROM THE CFS AND IRI MULTI-MODEL ENSEMBLE. THE CFS SUGGESTS ABOVE MEDIAN PRECIPITATION AMOUNTS FOR THE PACIFIC NORTHWEST AND NORTHERN ROCKIES, WITH ADDITIONAL SUPPORT FROM COMPOSITES.. ESPECIALLY NEAR THE NORTHERN ROCKIES. THE CFS AND IRI MODEL PREDICT ABOVE MEDIAN PRECIPITATION AMOUNTS FOR SOUTHWESTERN ALASKA, WITH SOME ADDITIONAL SUPPORT FROM SMLR.

In my opinion, I believe the predominant storm track will see systems come ashore in the Pacific Northwest (U.S. and Canada) and sweep across the plains, sometimes digging southeastward before making a turn toward the Great Lakes area.

[VoodooCadillac]

Don - you're consistently amazing and much appreciated - but we have a much higher authority in the mountains of North Cackalacky:

http://woollyworm.com/

Don't be intimidated - it's not really a fair comparison. You're the best in the "human" category.

[Steve H.]

Don, I appreciate your climatological and statistical use of data in predicting weather for the upcoming winter, and its the correct way to approach forecasting since there are really no other tools available to make a plausible forecast outside of observed data, but this is a winter that I really wished I lived back in the Northeast cause my gut tells me that they may experience a good "old Fashioned" winter this year. Don't know why I feel this way. Maybe it is the sudden "off" switch on the hurricane season and the onset of the dry season here in Florida. But it seems that the potential for blocking in the north atlantic, coupled with La Nina, could put enough cold air in the NE with an active southern branch of the jet stream that could set the stage for some stormy weather for the folks in the midwest and Northeast. Just a gut feeling here, but I feel the folks from the PA line north may be in for some treats this winter season. Thanks for all your insight during the Hurricane season. I look forward to hearing from you in June again.