WEATHERAmerica Newsletter, Saturday, September 14, 2024; EXTENDED PERIOD FORECAST

[Larry Cosgrove]

EXTENDED PERIOD FORECAST

(Between Day 11 And Day 15)

 

Two Likely Outcomes: The Atlantic Basin Is Still Tropically Active, And Cold Air Will Stay Above The Arctic Circle (For Now, That Is....)

CIMSS (3)

WMO/CMA

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

NOAA/PMEL

NOAA/CPC

ECMWF

HPRCC/University Of Nebraska (2)

Environment Canada

ECMWF (3)

TropicalTidbits.Com (Dr. Levi Cowan) (6)

With the first half of the 2024 hurricane season coming in far short from official projections, many that I have talked to have (predictably) written off the entire forecast as a huge bust. You will read various and sundry excuses such as the "QBO was stopping the tropical waves" to "Africa kept all of the moisture" and of course the ever-popular "MJO was not in the proper phase". But when looked at objectively, the Saharan Air Layer was immense and infiltrated most ITCZ impulses, the (shearing) upper westerlies hung around in July, and the ITCZ remained focused on equatorial Africa and not the Atlantic Basin. La Nina does not mean instant overdevelopment of disturbances, and you will find other such episodes that had a slow start.

But then again, most -ENSO years are going to surprise you with cases of super-intense storms and widespread/numerous output of late season tropical cyclones. I will stand by my original call of 18 named storms, 10 hurricanes, and 6 major storms. The current roster of developed warm-core cyclonic circulations is 6 named, 4 hurricanes, and 1 major. I emphasize a long-lasting season with clustering between now and Halloween. There is still a threat for a high-impact system affecting the entire Eastern Seaboard between September 30 and October 15. Most schemes show a broad, but negative-tilt trough complex over the eastern half of North America, with a weakness across the eastern Gulf of Mexico and Florida Peninsula. This plays into the linear wave progression that has linked with the remnants of Francine and a disturbed area below South Carolina. I also should mention that the subtropical westerlies in the Pacific Basin have only advanced to just past the International Dateline; the earliest these winds could reach the middle of the equatorial Atlantic Basin would be in about a month. Lastly, La Nina is approaching the moderate strength range in sector 3.4, while the entire field of  warm waters between the Americas and the Cape Verde Islands is much warmer than normal. All of this should tell you that the useful malaprop "It ain't over 'til it's over" applies here. Give it time, folks. But next time, I would advise not throwing "record numbers" out like candy.

Speaking of warm, the abundance of very warm air temperatures on the American forecast models would give many the impression that there is no cold air anywhere in North America. The GFS and CFS series often go into this "blowtorch" mode in the fall, as a result of a built-in model error. I suspect that many living in Canada and the USA will have a warm fall, with the only disruption being the passage of a Pacific Ocean-associated cold front or tropical cyclone landfall and track. The CanSIPS October forecast shows what I think is the proper set-up from now until Halloween.

One last thing: I am seeing some changes in the global pattern which have led me to alter some aspects of the North America DJF 2024-25 winter season. I would advise keeping an eye on the evolution of a southern branch jet stream and a deep Gulf of Alaska vortex. There are some aspects of the 2007-2008 period that could appear in the months ahead.

 

Prepared by Meteorologist LARRY COSGROVE on 
Sunday, September 15, 2024 at 1:00 A.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 2024 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.