Humberto rapidly strengthened to a hurricane early Friday and is forecast to ramp up into a formidable major (Category 3 or stronger) hurricane this weekend, but it’s the disturbance to Humberto’s west that’s expected to develop and threaten the southeast U.S. – likely as Imelda – by late weekend and early next week.

Though still entangled with the mountainous terrain of Haiti and eastern Cuba, the strong disturbance dubbed Invest 94L will lift northward into the Bahamas today and Saturday, where conditions will favor the formation of Imelda, the next named storm.

Just how strong Imelda becomes is complicated by the orientation of upper-level winds associated with a sharply tilted jet stream dip over the northeastern Gulf. Until the system pulls away from land and consolidates a defined circulation either later today or on Saturday, we won’t know where it’ll stand relative to the upper-level wind configuration that’ll dictate its future strength.

Friday morning intensity aids for Invest 94L (would-be Imelda). Until the circulation is clearly defined, expect wide swings in intensity forecasts. A tropical storm or hurricane looks likely by later this weekend as it moves through the Bahamas. Credit: cyclonicwx.com.

Nevertheless, guidance is in good agreement with at least steady organization and strengthening of Imelda this weekend as it stays east of Florida then possibly bending back west toward the Carolinas and southeast U.S. by next Monday into Tuesday.

Probability of the center of Invest 94L or future Imelda passing to within about 100 miles of any given location based on our most reliable global forecast models. The deterministic European model is noted in red and the American GFS deterministic run is noted in green. The black line is the average of all tracks. Although the average line indicates a track offshore and to the east, it’s being distorted by timing differences in the ensembles, with some slower members skewing the average. In this case, the average line is misleading, as most scenarios suggest a turn toward the Carolinas. Credit: Tomer Burg.

Growing concern for major flood threat to the Carolinas

We first discussed in this newsletter on Wednesday the pattern that could promote an upcoming flood event regardless of 94L’s development. The signals for a significant heavy rain and flood risk continue to grow for parts of the southeast, especially for the South Carolina Lowcountry to North Carolina and southern Virginia.

The setup this weekend could produce a Predecessor-like Rain Event or PRE well ahead of future Imelda. A PRE is a heavy rainfall event that can occur hundreds of miles north of a tropical system from a channel of rich tropical air flowing toward a frontal zone.

Total Precipitable Water or TPW forecast for Saturday afternoon from the European Centre (ECMWF) forecast model. TPW is a snapshot of how much water could be wrung out of the atmosphere instantaneously and is a gauge for the “soupiness” of an airmass. Red/magenta/purple/blue colors tell us there’s abundant moisture for weather systems like tropical cyclones or fronts to tap. The tropical air from 94L or future Imelda will be funneled toward the Carolinas this weekend where an upper-level low pressure area may worsen heavy rainfall as part of a Predecessor Rain Event or PRE ahead of the storm’s impacts early next week. Credit: Weathermodels.com.

These PREs are usually worsened by the presence of a nearby upper-level area of low pressure – like the one forecast this weekend over the Tennessee Valley – that help trigger the atmosphere to wring out the copious tropical moisture overhead. An extreme version of this happened last September in western North Carolina ahead of Hurricane Helene.

The other concerning part of this forecast for heavy rainfall is the possibility that future Imelda could slow or stall as it approaches the coastal Carolinas on Monday and Tuesday. This is a scenario favored by some of our better-performing forecast ensembles like Google’s AI-based DeepMind hurricane model and the European model ensemble system.

Forecast low-pressure tracks for Invest 94L/future Imelda from Google’s AI-based DeepMind hurricane model. Most scenarios depict a path east of Florida that turns westward toward South Carolina for early next week but slows or stalls near the Carolina coast or just inland, which would heighten the heavy rain and flood threat. Credit: Weathernerds.org.

Forecast low-pressure tracks from the European model ensemble system through early next Wednesday, October 1, 2025. Models have largely come around to suggesting a threat to the southeast coast centered on South Carolina for next Monday and Tuesday. Credit: Weathermodels.com.

We won’t be able to nail down the details of the flood threat until we have a better sense of how much future Imelda might strengthen and where it will track, but interests from southeast Georgia through the Carolinas and into southern Virginia should closely monitor the forecasts this weekend. Expect forecast rainfall totals to increase as we iron out the details in the days ahead.

Total rainfall forecast through next Wednesday morning (October 1, 2025) from the National Weather Service Weather Prediction Center. Credit: Pivotal Weather.

Humberto rapidly strengthening over the central Atlantic

Humberto is wasting no time strengthening today. It became a hurricane earlier today and already has cleared out an impressive eye as explosive thunderstorms encircle the center.

The borderline Category 2 hurricane is well on its way to major (Category 3 or stronger) hurricane status and the forecast now calls for it to top out as a formidable Category 4 hurricane this weekend over the western Atlantic.

The good news is models suggest the core of Humberto should split the uprights between Bermuda and the U.S. next week, but the hurricane will pass close enough to Bermuda to bring bands of heavy rain and strong winds to the British Overseas Territory by next Tuesday into Wednesday.

Probability of Humberto’s center passing to within about 100 miles of any given location based on our most reliable global models. Guidance suggests Humberto’s center should track west of Bermuda next Tuesday and Wednesday but it’ll pass close enough to bring strong winds, heavy rain, and dangerous surf to the British Overseas Territory. Interests in Bermuda should continue to monitor the forecasts closely as Humberto is expected to be a powerful major hurricane as it nears. Credit: Tomer Burg.

Residents and interests in Bermuda will want to follow this one closely, as Humberto is expected to be a powerful hurricane as it makes its closest approach next week.

Although Humberto’s nearby passage could possibly slow future Imelda as it approaches the Carolina coast, as we discussed in Thursday’s newsletter, the two systems should maintain enough distance that they don’t interact significantly.

It’s worth noting that if Humberto strengthens into a major hurricane this weekend as forecast, it would be the first time since 1935 that the Atlantic has gone 3 for 3 in the first 3 hurricanes of the season becoming majors (Category 3 or stronger).

Gabrielle wallops the Azores

Although Gabrielle technically lost its tropical characteristics yesterday as it approached the Azores, transitioning into a powerful extratropical storm, its center ripped through the central group of the Portuguese islands, bringing wind gusts to 122 mph at Horta Airport, which is located at about 118 feet elevation on Faial Island, around 5 AM local Friday (1 AM ET Friday).

The center of the now extratropical storm is several hundred miles east of the Azores and quickly accelerating away. The weakening extratropical storm will bring blustery weather, heavy rain, and large waves to coastal Portugal this weekend.

Imelda could form by this weekend and threaten the southeast US early next week

Humberto rapidly strengthens over the open Atlantic, but it’s the system to the west that could threaten parts of the southeast US as Imelda early next week

Growing concern for major flood threat to the Carolinas

Humberto rapidly strengthening over the central Atlantic

Gabrielle wallops the Azores

About The Author

Michael Lowry