WEATHERAmerica Newsletter; Saturday, September 27, 2025; SHORT RANGE, TROPICAL SYSTEMS OUTLOOK

[Larry Cosgrove]

SHORT RANGE, TROPICAL SYSTEMS OUTLOOK

(Through The Next 72 Hours)

 

Major Hurricane Humberto

Humberto is the second hurricane to reach Category 5 levels, and its excellent presentation over a shear-free, warm-water environment is bad news if the system targets Bermuda in about 72 hours. But Humberto is being steered by the frontal structure and Tropical Depression 9, an alleyway running from Cuba and Haiti northwards into New England. There is near-complete agreement among the various forecast models that this intense storm will be picked up by a broad 500MB southwest flow once it passes through or east of Hamilton. Just like Erin and Gabrielle before it. 

Tropical Depression 9

Humberto could briefly pull what will most likely be "Imelda" eastward away from North Carolina around October 1. But caught in that very obvious weakness and diffuse frontal structure across the Southeast, a lurch back into VA and NC seems likely. Could the circulation produce a torrential rain event in the Carolinas and Virginias? Possible if the low stalls with a front attached. If the remnant sticks around long enough, interaction with a sharp oncoming 500MB trough and surface cold front out of the Prairie Provinces and Ontario could prove to be a huge problem for Appalachia through the Interstate 95 corridor during the second week of October.

Hurricane Narda

Southwest flow aloft is shearing Hurricane Narda apart between Hawaii and Baja California. This feature is partly responsible for the false monsoon across the Desert and Intermountain Regions, since the shearing mechanism also is an advection agent. Narda should soon cease to exist.

Possible Gulf Of Mexico /Tehuantepec Disturbance

There is more trouble than you might think over the equatorial eastern Pacific Ocean. There is still a somewhat fragmented Central American gyre that continues to produce tropical disturbances from the Rio Grande Valley southward to Panama. I suspect that this highly convective feature will produce as much as three tropical cyclones during the next two weeks. If a 500MB weakness also lines up through the Gulf of Mexico, it may be possible for any new storm to move through the Isthmus of Tehuantepec into the Bay of Campeche. And possibly, by extension, reach the very warm waters of the Gulf of Mexico. The western and central Gulf Coast will still be vulnerable for a warm-core storm through the month of October.