WEATHERAmerica Newsletter, Saturday, October 18, 2025; EXTENDED PERIOD FORECAST

[Larry Cosgrove]

EXTENDED PERIOD FORECAST

(Between Day 11 And Day 15)

 

Reminders That, Despite Cold Frontal Passages, The Winter Outcome Is Far From Settled Yet

CIMSS (2)

NOAA/NOHRSC

TropicalTidbits.Com (Dr. Levi Cowan) (3)

NOAA/PMEL

NOAA/CPC

ECMWF

IRI/Columbia University

HPRCC/University Of Nebraska (2)

Environment Canada

WeatherBell (8)

I am simultaneously putting together the DJFM Winter Outlook, and feel it wise to give all looking at a mostly very warm October some "hope" that the 2025-26 Low Sun Period will not suffer the same fate as most of the seasons since the fabled 2014-15 "Cold And Snow" debacle over the Midwest and Northeast. But some warnings must be issued to the readers who are getting excited about the large -AO styled blocking signature and an apparent strong cold frontal passage sweeping across North America on and after October 29. Some of the features that I look for in a real cPk or cA intrusion are present, such as the aforementioned Ridge over Hudson Bay into the Arctic Islands of Canada, and the possible ingestion of a hurricane from the Caribbean Sea into the potent upper trough and surface cold front somewhere in the Mid-Atlantic or New England around Halloween. But what of snow cover (almost nonexistent in North America) or durability of the high-latitude ridge complex (questionable). Another issue: the confirmed sequence of Gulf of Alaska and then Aleutian vortices, which in the past 45 days has brought extreme warmth to much of the continent. The big concern I have is that the longer-term climate control model members seem reluctant to keep a colder trend going outside of the Midwest/Great Lakes.

The almost-moderate La Nina signal at sector 3.4 is favorable for a -EPO/-AO/-NAO styled colder winter if the deviations slowly moderate as computer schemes suggest will happen. The projections take the ENSO SST forecasts to neutral/positive territory by April 1. If you want a cold winter to occur, the best odds on occurrence of cold, snow and/or ice are when the 3.4 sector readings remain close to flat neutral, with occasional negative or positive percolations. I suspect that it will take another 2.5 months before a reliable warm West/cold Central/mild East sets up. There will be occasional visits to an amplified, cold-inducing 500MB flow, and I would not be surprised to see this DJFM mimic that of the year previous. 

Of course, I always look for a prominent "starter" event like a deep trough or combination with a western Atlantic Basin hurricane. There is good support for a major system affecting the Greater Antilles in the longer term, then accelerating north and possibly merging or phasing with a big cold trough complex close to the East Coast. It is very early in the game, but the waters are very warm and the cPk air mass will likely head toward Texas and Mexico before pushing through Dixie. If a gap is present, the big cyclonic circulation may track due north or possibly undergo a jog toward Virginia, the Mid-Atlantic or New England. For all of this to happen, we must see a strong Rex or Omega block in Nunavut AR. And should this cyclonic path occur, we can finally start to get rid of the "Indian Summer In Overdrive" pattern.

 

Prepared by Meteorologist LARRY COSGROVE on 
Sunday, October 19, 2025 at 12:40 P.M. CT

Disclaimer: 
The previous statements are my opinions only, and should not be construed as definitive fact. Links provided on this newsletter are not affiliated with WEATHERAmerica and the publisher is not responsible for content posted or associated with those sites.

Copyright 2025 by Larry Cosgrove

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