La Nina is gradually returning. The Multivariate ENSO Index (MEI) has dropped to -0.74 in October, well into weak La Nina territory. The tropical Pacific sea surface temperatures all the way from South America to beyond the dateline are back below normal. The North Pacific as a whole remains strongly in the cold mode (negative PDO).
The Atlantic is weakly in its warm mode (Atlantic Multidecadal Oscillation is positive). The sun recently showing slight signs of life is still at solar minimum levels. The winds in the stratosphere over the tropical Pacific are blowing anomalously westerly) in their Quasi Biennial Oscillation.
All these conditions point to another cold winter in all but the southeastern United States, most of Canada, most of western Europe, eastern and southern Asia. Expect a coolish summer in South Africa, Indonesia and South America. Snow should be heaviest relative to normal from the northern and central Rockies, northern and central Plains, Ohio Valley to the Mid-Atlantic and southeastern New England. Snow to north should be less than last year but snowcover will be most persistent there.
WHAT TO WATCH FOR
Should La Nina become stronger than expected, the southeast warmth will be more pervasive and extend further north and west the second half of winter. That is the classic pattern in west QBO La Ninas.
Most strong La Ninas as was the case last winter reprise in a weakened form the second winter especially if they weakened as much a this one did during the intervening summer.
The dominant factor may be the solar minimum west QBO which shows the Canada and northern tier cold trough and the North Atlantic Blocking.
The low solar during this solar minimum phase of the 22 year Hale solar cycle shows low variability. This was the case last winter/spring certainly. (Willett)
Fighting this persistence is the weak La Nina which suggests more variability than last year when the La Nina was stronger.
One of the most persistence feature from the fall season to the winter season is the storm track. Storm tracks preview future tracks although you need to make some adjustment for low level cold air which shifts the tracks slightly south and east.
For some amazing photographs from the New England snows of last winter courtesy of Ric Werme near Concord, NH see his site here.