NOAA WINTER OUTLOOK WARMER...
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NOAA WINTER OUTLOOK UPDATE (MY THOUGHTS)
Some of you have heard and even messaged me about the revised winter outlook recently issued by NOAA. Based largely on what it believes will be a stronger than than originally anticipated La Nina, the outlook is warmer here in the Midwest.
Precipitation has increased some since the previous outlook and looks like this
The results were heavily based on the IRI seasonal forecasts with inputs from the NCEP-CFSv2, CanSIPsv2, and COLA-RSMAS-CCSM4, and GFDL-SPEAR models. This month’s forecasts also use the new climatological normal period 1991-2020.
As I mentioned, the biggest driver in this warmer outlook is the developing La Nina which is forecast to reach near moderate strength. Here are the model plumes, focus on the statistical average which near the heart of winter is around -0.6 below the neutral phase of 0.
Stronger La Nina's associated with cold water over the tropical Pacific tend to create a formidable zonal flow (west to east jet stream) which makes it harder for Arctic intrusions to enter deep into the United States. This favors cold in the northern tier and warmth over the southern half of the nation. In general, strong La Nina's tend to bring above normal temperatures to much of the nation.
For those of you who read my winter outlook several weeks ago, you recall I favored a winter that would be somewhat colder than average with near normal precipitation, perhaps a bit above. I also indicated that with the proper sea surface temperatures and teleconnections of the MJO and Arctic Oscillation, a relatively harsh winter was on the table. I looked for a faster start to winter as well with a colder and potentially snowier December than in recent years. Under the what could go wrong section, my "biggest concern" was that the La Nina turned out to be significantly stronger than forecast creating a temperature bust with much of the winter being influenced by modified Pacific air masses substantially warmer in nature.
I still haven't seen any strong reason to throw my outlook under the bus. Overall, the La Nina is doing about what was anticipated and until I see it go higher than anticipated I will hang tough. We've also got the sudden stratospheric warming going on which is unusual this early in the year and a wild card for cold.
Something else that's encouraging to me is the current seas surface temperatures in the Pacific. The top analog right now to where we are this year is 2008. Both were La Nina years and both show strong similarities, 2021 being a steroidal version of 2008. Also, the Atlantic this year is warm off the east coast which argues for a southeast ridge. Back in the Midwest that would put us within the mean trough and near the storm, a fun place to be. Ideally not overly cold but cold enough for snow systems.
2007 also is in the mix and incidentally was a moderate El Nino winter. I looked up seasonal snowfall in the winters of 2007-2008 and 2008-2009 in Cedar Rapids. Those were big hitters with 56.6 and 45.5 inches respectively.
About three weeks ago 2013 was my best SST analog, you can see the early October comparison of 2013 to 2021.
The winter of 2013-14 was a tough one in my area, cold and snow ran the table all winter. What's interesting about 2013 is that the warm water in the NC Pacific in October moved into the Gulf of Alaska by early winter forcing a strong ridge to form off the west coast. That generated strong Arctic highs that repeate