Weather Blog: September 26 2025 4 PM (Tropics)

WHAT MIGHT BECOME IMELDA COULD POSE A RISK TO THE SOUTHEAST UNITED STATES 

A tropical wave (currently identified as Invest 94L) approaching the southeast Bahamas might develop into a tropical storm or even hurricane and affect portions of the Southeast United States, especially South Carolina and North Carolina, early next week.  If that should happen, it will be named Imelda.  Let’s first, however, take a look at Humberto, now a hurricane.

Humberto

As of this issuance, Hurricane Humberto is showing signs of rapid intensification as it moves closer to a region of warm sea surface temperatures, ample moisture, and less vertical wind shear.  Humberto will likely become a major hurricane this weekend and is likely to reach category 4 intensity.

There is now fairly high confidence on the track of Humberto, which should move west, northwest, and then north of Bermuda with the center remaining over the open ocean.  Humberto is expected to track around the western periphery of deep high pressure (essentially a “Bermuda High”) and then be “picked up” by a vigorous mid-level trough of low pressure that passes through Atlantic Canada and into the North Atlantic next week.  This will cause Humberto to eventually accelerate to the northeast and be mainly a concern for the shipping lanes.

Bermuda may be influenced by the outer fringes of the storm with gusty winds and high waves but should avoid anything like a close (or even near) hit.  Besides impacting Bermuda, swells from Humberto may produce moderate to high surf along portions of the U.S. east coast, especially the ocean side of Long Island and the ocean shorelines of the Cape and Islands next week.  Also, the radius of hurricane and tropical storm force winds should increase as the storm gains latitude to the northwest and north of Bermuda.   Any mariners contemplating a trip from New England to Bermuda this weekend or next week should monitor latest developments and consider alternate plans.

Invest 94L (Likely to be named Imelda)

This tropical wave will likely move into the vicinity of the Bahamas this weekend and be in an environment of warm sea surface temperatures and light vertical wind shear, which should favor development into at least a tropical depression and likely a tropical storm and possibly a hurricane.  Reviewing the various hurricane-centric and global models, there is considerable uncertainty as to how strong this system will become.

There is also uncertainty in its track in part due to the proximity of Humberto to the east.  The consensus of numerical prediction models depicts Invest 94L to move to the northwest to somewhere along the South Carolina coast early next week – in essence being steered toward a weak upper trough over the Southeast.  However, there is a significant subset of models (including a few ensemble runs of the ECMWF and GFS) that keep this system offshore and then shift it to the east in essentially an orbit about Humberto with the result of the system never making landfall.  There are even a very small minority of ensemble runs that start to bring the system close to the South Carolina coast only to shift it east under the influence of Humberto but then “break away” from Humberto’s influence and head back west or even north to track just off the mid-Atlantic and Northeast U.S. coast.  The bottom line is that there is much uncertainty but the trend of recent model projections has this system getting very close to or onshore the Southeast coast (most likely South Carolina).  Hence, people along the Southeast U.S. coast should monitor later information on this storm from the National Weather Service.

Potential U.S. Impacts If Imelda Forms

It’s not possible to get specific on location, timing, or severity of impacts given uncertainties in the projection of both intensity and track.  Nevertheless, people in South Carolina, North Carolina, and even Georgia should monitor future developments of this system and ensure they have a hurricane plan in place.  The system potentially could produce a storm surge, damaging winds, and heavy rain.  If the storm should move onshore, it could produce serious flooding rains even well inland across the southeast U.S.  Even if this system remains offshore, it will likely produce large swells that in turn could result in high surf and dangerous rip currents along portions of the exposed eastern U.S. coast.

Next Message

This message will be updated Saturday.

About this Blog and Disclaimer

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 serves 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 eastern 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.

Blue Hill Observatory and Science Center (BHOSC)

The BHOSC maintains a continuous daily observation record that dates from February 1, 1885 without interruption and provides educational information on weather and climate to area students and the community at large.  Your support of BHOSC is much appreciated and enables this nonprofit organization to maintain the long-term climate record at the Blue Hill Observatory (longest continuous record in North America) and provide valuable educational resources on weather and climate via outreach to schools, site visits/tours, webinars, and conferences.  For more information on the Blue Hill Observatory and Science Center, explore bluehill.org.

Message issued by:

Bob Thompson

Retired National Weather Service Meteorologist

Blue Hill Observatory and Science Center Board member