Significant Weather Blog: Friday, October 10, 2025 7 PM

SOME COASTAL FLOODING AND BEACH EROSION LIKELY ALONG PORTIONS OF THE SOUTHERN NEW ENGLAND COAST SUNDAY AND MONDAY ESPECIALLY CAPE AND ISLANDS DURING THE LATE MONDAY HIGH TIDE

Coastal Storm Overview

The various numerical weather prediction global models have come into reasonably good agreement with the development of a coastal low off the east coast.  The incipient surface low pressure center will move northeast from Florida and then intensify off the North Carolina coast as it is infused with energy from a fairly vigorous mid latitude trough moving southeast from southern Canada.  Although this system may have some subtropical characteristics, it will likely manifest itself more as an extratropical storm. Although explosive cyclogenesis isn’t expected, hybrid storms such as these often carry a bit more of a punch than first meets the eye and so should not be dismissed too quickly.  An important ingredient to this event is fairly strong high pressure that will be anchored over the Canadian Maritimes.  This high pressure will help block the coastal storm from moving too quickly and will also result in a relatively tight pressure gradient between the high center and coastal low center.  It is that tight pressure gradient that will cause strong east to northeast winds from the Carolina coast to the southern New England coast.

Impact Overview

Portions of the Carolina coast (including the Outer Banks) and the mid Atlantic coast will likely experience high winds, heavy rain, coastal flooding, and very serious beach erosion.  For southern New England, fairly strong gusty winds, pockets of coastal flooding, and beach erosion appear likely late Sunday through Monday.  The strongest onshore east to northeast winds will likely occur during Monday, and the greater risk of any minor to moderate coastal flooding as well as significant beach erosion looks to be about the Monday late afternoon high tide.  Although there is a risk of some coastal flooding along vulnerable Massachusetts east coast locations, it looks as though the Cape and Islands will be most prone to beach erosion (especially during the late Monday afternoon high tide).  At least some beach erosion may occur along the Rhode Island coast as well, and coastal flooding looks to be fairly likely along the Long Island Sound shoreline, especially west of New Haven.

The rainfall forecast remains rather uncertain as there could be a fairly sharp cutoff to the north.  The model consensus, however, indicates periods of rain spreading north from the south coast Sunday evening and continuing through Monday into Monday night across most of southern New England.

Specific Impacts

Wind:  East to northeast winds will increase Sunday and probably peak late Sunday night into Monday.  Over the Cape and Islands, gusts to 40 mph are likely by mid or late Sunday afternoon and increasing to 50 to 55 mph Sunday night into Monday (highest over the Islands).  Along the Massachusetts east coast north of Cape Cod, east to northeast winds may gust to around 45 mph late Sunday night through Monday.  Scattered tree damage is possible in coastal areas, especially south of Boston.  The strong winds will result from what will be a tight pressure gradient between the low pressure center just offshore and a relatively strong high pressure center anchored over the Canadian Maritimes.

Coastal Impacts:  The strong onshore wind will cause areas of coastal flooding and beach erosion along much of the United States east coast.  Although the greatest impact may be along the North Carolina outer banks and the Delaware/Maryland open coast, beach erosion and some coastal flooding will likely extend further north to southeast New England as well.

More specifically for southeast New England, the increase in onshore east to northeast winds may occur sufficiently soon to produce a storm surge of 1 to possibly 2 feet and waves to 10 feet along east and southeast facing ocean shorelines of the Cape and Islands by the time of the mid to late Sunday afternoon high tide, which is fairly high astronomically to begin with (10.9 feet above Mean Lower Low Water (MLLW) in Boston Harbor).  This may cause pockets of coastal flooding and at least some erosion, especially along vulnerable Cape and Island shorelines.

The storm surge will likely build to between 2 and 3 feet along the Massachusetts east coast (including the Cape and Islands), and near shore waves may build to 15 to 20 feet during Monday with the highest storm surge and waves along exposed Cape and Island shorelines.  The early Monday morning high tide is not particularly high and so the impact then may be fairly minor even though the wind may be really cranking by then.  The higher astronomical high tide in the late afternoon/early evening on Monday may be more problematic with considerable beach erosion and areas of minor to possibly moderate coastal flooding along vulnerable areas of the Massachusetts east coast from Newburyport/Plum Island to the Cape and Islands.  By that time there will have been a longer duration of elevated water levels and significant wave action by the persistent east to northeast winds.  The most severe erosion will likely be experienced along open ocean facing beaches on the Cape and Islands but at least some erosion as far north as Plum Island cannot be ruled out.  Some erosion may persist even into Tuesday along the Massachusetts east coast depending just where and how long the storm remains in the vicinity.

There may also be some erosion issues along the Rhode Island coastline even though the wind will not be so much onshore due to large waves propagating to the shore.  The Misquamicut Beach area could be especially vulnerable.

The Long Island Sound shoreline of western Connecticut may also be vulnerable to at least minor to moderate coastal flooding Sunday afternoon and late Monday afternoon as strong east to northeast winds pile water into the western portion of Long Island Sound.

As noted in the previous blog, we are fortunate that this system will occur after the peak of the astronomical high tides that have been occurring the latter part of this week.  These “King Tides” occur when the gravitational pull of the Moon and Sun act in conjunction.

Rain:  The extent, duration, and amount of rain is highly sensitive to the exact track of the storm and still remain rather uncertain.  A consensus of models suggest rain reaching the south coast of New England sometime mid to late Sunday afternoon and spreading across most, if not all, of southern New England Sunday night into Monday morning.  Periods of rain may persist into Monday night or even Tuesday morning.  A model consensus places the heaviest rain across CT and RI, and southeast MA where 1 to 2 inch totals are possible, but this is subject to change.

Marine:  This coastal storm will likely have a very significant marine impact given the strength of surface winds and the duration.  Gale to Storm Force winds are likely across the southern New England coastal waters, strongest east and south of the Cape and Islands late Sunday through Monday.  Waves may build late Sunday night and Monday to 15 to 20 feet across the eastern Massachusetts near shore waters exposed to the open ocean and even higher between 20 and 25 feet offshore to the south and southeast of the Islands.  Ferry service to Block Island, Martha’s Vineyard, and Nantucket may be affected Sunday afternoon through Monday.  Travelers to any of the islands should check with the appropriate ferry office and be prepared to adjust plans at the advice of ferry personnel.

Next Message

Will continue to monitor and will update this message if there looks to be a significant change.  All those interested in this event or possibly impacted should monitor the latest forecasts, warnings, and statements from the National Weather Service (weather.gov/box for most of southern New England).

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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 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.

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.

Southern New England Weather Conference

If you are reading this message, then you probably have an interest in the weather and/or climate of our region.  Consider signing up for the Southern New England Weather Conference to be held Saturday October 25 at the Meditech facility in Canton.  There is a fascinating slate of prominent speakers lined up! Go to bluehill.org to register.

Message issued October 10, 2025 by:
Bob Thompson
Retired National Weather Service Meteorologist
Blue Hill Observatory and Science Center Board member