WEATHERAmerica Newsletter, Saturday, October 2, 2021 at 9:00 PM CT; Extended Range Discussion

[Larry Cosgrove]

EXTENDED PERIOD FORECAST

(Between Day 11 And Day 15)

 

The Expected Pattern Change, And Where It May Lead To For North America

CIMSS (2)

WMO/GRAPES

NOAA/CPC

TropicalTidbits.Com (Levi Cowan) (4)

NOAA/PMEL

HPRCC/University Of Nebraska (2)

Environment Canada

TropicalTidbits.Com (Levi Cowan) (5)

TrueWx.Com (3)

If I had to pick a title for this longer term forecast, and the upcoming NDJFM seasonal outlook as well, it would likely be "Getting To Know The Gulf Of Alaska Low". Along with that designation, I might throw in a subtitle, "How Those Typical La Nina Remarks Are Most Likely Going To Be Stupid". 

When looking at the attached graphics, you see that we have a fairly well-defined La Nina episode in its building phase, probably reaching moderate status at its peak in December and January. Also, a review of satellite imagery has a very impressive subtropical jet stream that originates with convection inspired by the Madden-Julian Oscillation straddling the Maritime Continent into the central equatorial Pacific Basin. A vigorous streak of the polar westerlies has been boosted by the recent injection of energy from Typhoon Mindulle, now an extratropical cyclone passing over the Aleutian Islands. Lastly, the former Major Hurricane Sam is about to merge with a deep 500MB low nearing Newfoundland. These events are a very neat, easy-to-read feature map of the upcoming weather pattern for North America.

The numerical model graphics show the near-constant presence of a Gulf Of Alaska Low. This cold pool gets re-energized every time tropical disturbances (some of them typhoons) move up from east of the Philippines and Japanese Archipelago. Some of the impulses will progress east-northeast toward a closed low near Hawaii (the start of a Kona Low formation). It may take a while, but by November the cloud streak across Baja California into Texas will be thicker with embedded important precipitation. With the Southwest missing the dewpoint fetch, eventually the pulsing cold upper gyre entering the Pacific Northwest will have an incentive to phase with the southern branch. When it does, the Upper Midwest, Great Lakes and St. Lawrence Valley will be faced with a colder trend, and glimpses of snow threats that will escalate next month and in December as well.

You will realize bits and pieces of these trends during the next four weeks. There will be an ongoing danger that a tropical cyclone may organize in either the Caribbean or Sargasso Seas. These impulses could be quite strong, and interact with upper level lows that are passing under ridging over the eastern half of Canada and Greenland. This is essentially a cool West vs. mild/warm East alignment, but some of the polar air masses may arrive in areas to the right of the Mississippi Valley and Great Lakes during the week of Halloween.

Synoptic analogs (not ENSO, solar, or modeled) for this autumn and winter are 1976, 1995, 2007, and 2020. Project forward to get an idea how the December through March time frame might turn out. 

 

Prepared by Meteorologist LARRY COSGROVE on 
Saturday, October 2, 2021 at 9:00 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 2021 by Larry Cosgrove

All rights reserved.
This publication may not be reproduced or redistributed in whole or in part without the expressed written consent of the author.

ReplyForward