WEATHERAmerica Newsletter, MEDIUM RANGE OUTLOOK, Saturday, July 26, 2025

[Larry Cosgrove]

MEDIUM RANGE OUTLOOK

(Four To Ten Days From Now)

 

How Far South Will The Cool Canadian Air Mass Reach?

UQAM Meteocentre (4)

TwisterData.Com (4)

TrueWx.Com (4)

College Of DuPage Weather Laboratory

I do not expect that the impressive heat ridge now straddling much of the USA is just going to get up and vanish. To be sure, the Hudson Bay Low looks strong enough to kick the hot air out of the northern third of the nation to the right of the Rocky Mountains. But most of the 500MB forecasts are careful to show the Sonoran heat ridge (south central states) and the Bermuda High making a sort of "rebound" in about 9 or 10 days. There may be a frontal structure that provided an incentive for thunderstorm formation, roughly parallel to Interstate 70. Again, if a weakness is evident close to or just west of the Mississippi River, moisture and parceled lifting/forcing could produce plentiful rain and thunderstorms close to and just below 40 N Latitude. But in any event, I do not see a cooler regime getting into Dixie, and suspect that by the end of the medium range the heat and humidity will be approaching the maajor population centers of the Midwest and the Northeast.

Rebuilding Heat Ridge Vs. Tropical Cyclone Threat

ECMWF (4)

PivotalWeather.Com (4)

NOAA/PSL (2)

By now you may have read or heard about the ramping up of Cape Verde tropical cyclone threats via the ECMWF series and the various AI incarnations of the forecast models. The analog heat ridge outlines at 500MB are favourable for a trip from Cape Verde in Africa all the way to the Gulf of Mexico. If taken literally, any such storm would threaten the central/eastern Gulf Coast and then turn up along the Atlantic Coastal Plain (negative height anomaly near Boston MA...). Another issue is the expansion of the ridge complex with the weakness possibly showing up further west into Texas (vector wind projection shows this beautifully). The extremely hot air across the south central and Dixie states might be something that would occur just before an approach of a major warm-core storm. My feeling is that if the subtropical high expands north and allows some "room" along the shoreline from TX to FL, we could see a threat.