WEATHERAmerica Newsletter, September 6, 2025; EXTENDED PERIOD FORECAST

[Larry Cosgrove]

EXTENDED PERIOD FORECAST

(Between Day 11 And Day 15)

 

Waiting For Another Polar Air Mass. Or Maybe An Atlantic Basin Tropical Cyclone?

CIMSS (3)

WMO/GRAPES Beijing

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

NOAA/PMEL

NOAA/CPC

ECMWF

HPRCC/University Of Nebraska (4)

Environment Canada

WeatherBell (4)

TropicalTidbits.Com (Dr. Levi Cowan) (5)

Now that "meteorological summer" is finished, some conclusions can be drawn as to patterns emerging or receding, with emphasis on temperature, precipitation, and tropical feature anomalies. August brought the very warm temperature averages down in North America, with everything from a vibrant Rio Grande/Rocky Mountain-oriented monsoon to an impressive northern Pacific Rim storm track and Texas 500MB weakness in view. The Sonoran heat ridge tended to build into a West Coast thumb-projection signature (see the heat and fires in the Pacific Northwest as proof), while the Bermuda High pulsed strongly, but erratically west into the Corn Belt and Appalachia. The discontinuity between the ridge complexes led to a high dewpoint fetch shifting from the Mexican Cordillera to the Continental Divide and then through central Texas, which led to flood disasters and severe weather.

Then of course is the tropical cyclone season, running at a below normal pace with one major storm (Erin) that had few impacts to speak of. The parceled Saharan Air Layer has not been as  strong or as complete as last summer, but has managed to destroy many of the impressive ITCZ waves coming out of central Africa.Given the abundance of warm water in the Atlantic Basin, and the lack of shearing profiles aloft below 40 N Latitude (remember that the earlier advance of the upper westerlies in the Pacific Ocean has receded), I think we are far from done with the 2025 hurricane season. The peak day of September 9 through the secondary rise in storm number of October 5 should see an uptick in the amount of waves, depressions and named storms. It might mean that I need to walk down my earlier totals (22 named, 12 hurricanes, and 6 major cyclones), but the expected elimination of the Saharan Air Layer and strengthening of the Bermuda High will likely give new life to North American and island storm threats.

Most of the forecast guidance (analog and numerical model) points toward some hotter weather on both coasts over the next six weeks. But the importance of transient high-latitude ridging (see the Northwest Territories and Nunavut AR positive 500MB height anomaly) suggests that another polar air breakthrough will occur from the Prairie Provinces and Ontario into the Midwest and Northeast in Week 3.

 

Prepared by Meteorologist LARRY COSGROVE on 
Saturday, September 6, 2025 at 11:10 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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