I was digging through some data today and it leads me to believe that November (and winter) has a good chance of getting off to a cold start. Here's my thinking.
Recent runs of models, especially the EURO EPS weeklies have shown blocking developing at high latitudes. Above normal 500mb heights bridging the Arctic forces cold air and storminess to undercut the block and penetrate the U.S. Below you can see what the EPS shows at 500mb the last week of November. You can clearly see the blocking aloft (in red) and lower heights associated with colder stormy weather (blue) over the continental U.S.
If this holds it plays into a colder winter as well. You can see the blocking at northern latitudes forecast December-February on the EURO. JMA and Pioneer model developed by Joe D'Aleo.
The Pioneer of Joe D'Aleo
It's interesting to see the EPS going to that solution in November. That could be the start of the colder than normal winter these models are projecting.
The EPS weeklies also forecast negative phases of four major teleconnections starting in November. I'll put up the forecast teleconnection and then the associated temperature departures in November.
The EPO (Eastern Pacific Oscillation)
The NAO (North Atlantic Oscillation)
The AO (Arctic Oscillation)
The WPO (Western Pacific Oscillation)
The one teleconnection of five that does not lean cold in November is the PNA (Not until the very end of the month does it grow negative and cold.)
The other key indicator I'm looking at in the coming winter is sea surface temperatures, especially in the Pacific. Two things stand out. One is the developing week El Nino. The warmest water is focused on the central Pacific with cooler waters to the east (near South America) and west (near Indonesia). The other is the large amount of warm water in the North Pacific into the Gulf of Alaska.
Combined the two areas of warm sea surface temperatures would promote the west coast ridging that drives cold air masses into the country. Once again you can see the ridge over the warm SST's forecast over the Gulf of Alaska below.
The colder water in Indonesia would also tend to keep the MJO in the colder winter phases of 8, 1, and 2. That's a key factor when it comes to deep prolonged cold.
Precipitation and snowfall is a much more challenging aspect of long range forecasting as there's no way to know the precise track of individual storms. However, if indeed my belief of a colder winter verifies that increases the chance of at least normal snowfall. If the developing west coast ridge is where it seems to be heading, that would allow phasing of the polar and sub-tropical jets increasing the chances of more significant storms and heavier snows. If not, clippers would be more influential producing narrower bands of snow with lighter accumulations.
My hunch is that snowfall will end up near to above normal with widespread winter totals in the 30-40" range. Normal is about 32 here in Cedar Rapids.
Getting back to November if the cold comes as it appears, the odds of early snows increase. The EPS weekly means show this for snowfall through November 30th. The average date of the first 1" of snow in Cedar Rapids is December 2nd.
The control as common is even more aggressive with amounts that look like this. Significant early snows fall well into Missouri and southern Illinois. Needless to say this is a very bullish run of the weeklies. One that I would be thrilled to see verify but also one that I have serious doubts about.
Suffice it to say the signs are there for a pretty healthy winter. Hopefully the El Nino does indeed remain weak and focused over the central Pacific (Modoki). If so winter has plenty of promise. Roll weather...TS