Weather Blog: September 28, 2025 4 PM (Tropics)

REDUCED THREAT OF MAJOR IMPACTS FROM IMELDA FOR THE U.S. 

Tropical Depression Nine has strengthened into a tropical storm, named Imelda.  It now looks as though Imelda will make a sharp right turn before getting all that close to South Carolina and then head into the open ocean.  Meanwhile, Hurricane Humberto remains a major hurricane of category 4 intensity at the time of this issuance.  We will take a look at Humberto first and then Imelda

Humberto

Although there could be a few fluctuations in intensity, Humberto is expected to remain a major hurricane for another day or so.  As Humberto eventually turns more north and then northeast, it will encounter greater vertical wind shear and cooler ocean temperatures.  Also, as Humberto gains latitude, it will become larger with increasing radii of hurricane and tropical storm force winds.  This will result in exceptionally large waves (possibly between 40 and 50 feet along and just to the right of its track!) and swells that propagate very far from the storm.

In four or five days, Humberto will undergo an extratropical transition as it interacts with a vigorous upper trough passing through eastern Canada into the northwestern Atlantic.  Humberto will still be a formidable post tropical storm after transition with a large swath of storm force winds and hurricane force gusts.

Humberto will track west, northwest, and north of Bermuda.  Although Bermuda will be a considerable distance from the core of Humberto, the intensity and size of the hurricane will likely result in tropical storm force winds very near, if not over Bermuda, in addition to very high (possibly even damaging) surf.

Another consequence of Humberto will be large swells that will approach the eastern U.S. and Atlantic Canada coastline this coming week and likely increase the risk of dangerous rip currents once again along ocean exposed beaches.

Imelda

There have been a few consequential developments since yesterday’s message.  Tropical Depression Nine has intensified into a tropical storm and is now named Imelda.  There’s much greater clarity in the expected track.  Essentially all global and hurricane-centric models bring Imelda north-northwest to somewhere well east of northeast Florida and then depict a sharp turn to the east-northeast and continued motion to the east-northeast and further out to sea.  Having formed further south than projected by some of the models, Imelda will be influenced by major hurricane Humberto, which will halt Imelda’s northward motion and create a steering current for Imelda to move east-northeast.  There is now strong model consensus on this scenario.

A consequence of this shift in track further away from land and remaining over warm water is expected to be greater intensity than originally projected.  Imelda will likely not only intensify into a hurricane but very possibly to at least category 2 status.  However, Imelda will likely at some point cross Humberto’s wake of cooler water (since hurricanes induce upwelling of cooler water below the surface), which may cause some weakening of Imelda.

Impacts from Imelda

The threat of major impacts from Imelda to any portion of the Southeast U.S. coast has diminished due to Imelda staying further offshore than originally projected.  Imelda will be growing in intensity and to some extent in size, however, and bands of heavy rain with localized urban or poor drainage flooding is possible along the South Carolina and southeast North Carolina coastal region.  Gusty winds and high surf are also possible along the Georgia, South Carolina, and southeast North Carolina shoreline, but a worst case scenario would probably be a few tropical storm force gusts in the late Monday through Tuesday time frame.  People living or visiting along the South Carolina and southeast North Carolina coastal region are encouraged to monitor latest information from local National Weather Service offices.

Swells from Imelda will add to those from Humberto and cause a risk of high surf and elevated rip current risk along ocean exposed beaches of nearly the entire U.S. east coast, including ocean exposed beaches of Cape Cod and the Islands mid to late week.

Current track projections bring Imelda very close to Bermuda late Thursday with the potential risk of hurricane force winds, high surf and storm surge flooding, as well as flooding rains only a day or two after potentially experiencing tropical storm conditions from Humberto.  One potential saving grace is that Imelda may weaken a little as it crosses Humberto’s wake of cooler water.  Interests in Bermuda should closely monitor information from the National Hurricane Center and the Bermuda Weather Service given probable impacts from both Humberto and Imelda.

Next Message

This will likely be the last of the series of messages on Humberto and Imelda.  As always, check your local National Weather Service by going to weather.gov and clicking on the area of interest for latest forecasts and any watches and warnings.  For the latest information on any occurring or incipient tropical cyclones, check with the National Hurricane Center (nhc.noaa.gov).  Interests in Bermuda should very closely monitor information being provided by the Bermuda Weather Service (weather.bm).

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The National Weather Service monitors the weather 24/7 and updates forecasts, watches, and warnings as necessary.  For most of southern New England, refer to your local Weather Forecast Office for the latest forecast/warning information at weather.gov/box.  For information from other Weather Forecast Offices, go to weather.gov and click on the location of interest on the map.  For the latest information on Atlantic basin hurricane activity, access the National Hurricane Center website at nhc.noaa.gov.

A blog is issued when there is a potential risk of hazardous weather to southern New England and serve to provide background information regarding the significant weather with somewhat of an educational slant.  In the case of hurricanes, the author will attempt to issue a message when any portion of the United States coastline may be seriously impacted.  It’s intended to complement and not serve as an alternative to official forecasts issued by the National Weather Service.  Readers are urged to check National Weather Service forecasts and warnings for the most timely and updated weather information.  This weather message is solely produced by the listed author and does not constitute an official product of the Blue Hill Observatory and Science Center (BHOSC).

The frequency of this blog will depend upon the nature of the weather threat and availability of the author.  Thus, for the latest information on weather forecasts and warnings, refer to the National Weather Service, which monitors and forecasts the weather 24/7.

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Message issued September 28, 2025 by:
Bob Thompson
Retired National Weather Service Meteorologist
Blue Hill Observatory and Science Center Board member