Significant Weather Blog: Sunday, October 12, 2025 4 PM

SIGNIFICANT BEACH EROSION THROUGH MONDAY ALONG OCEAN FACING SHORELINES OF CAPE COD AND THE ISLANDS

Coastal Storm Overview

The coastal storm was evolving close to model projections, and no major changes from the prior forecast are expected.  The tight pressure gradient between blocking high pressure over the Canadian Maritimes and coastal low pressure stalling just off the mid-Atlantic coast will continue to cause strong east to northeast winds through Monday, slowly tapering off Monday night into Tuesday.  This will result in beach erosion and areas of coastal flooding during high tides this evening through Monday evening.  Severe beach erosion and moderate to major coastal flooding is expected along vulnerable shorelines from North Carolina north to New Jersey.  Minor to moderate beach erosion and pockets of mostly minor coastal flooding are expected along vulnerable shorelines of Long Island, Rhode Island, Cape Cod, and the Islands.

Current Conditions at 4 PM Sunday

Northeast or east northeast wind gusts had increased to 40 to 45 mph over the Islands, 35 to 40 mph over the Cape, and generally between 30 and 35 mph elsewhere along the exposed Massachusetts east coast.  The storm surge had increased to around one foot from the Cape and Islands to Boston.  Coastal waves had increased to 10 to 13 feet over the ocean east of Cape Cod as well as east and south of the Islands.  Rain had overspread most of southern New England and was falling heavily in a band across the Cape and Massachusetts south coast and moderate to heavy across southern Rhode Island and much of Connecticut.

Specific Southern New England Impacts

Wind:  Northeast or east-northeast winds will gust tonight and Monday to around 55 mph at times over the Islands and to around 50 mph at times over the Cape tonight and Monday.  This will cause scattered tree damage and likely pockets of power outages, especially since the trees are still leafed out.  Northeast winds will gust between 40 and 45 mph at times along the exposed east coast of Massachusetts from Plymouth north to outer Cape Ann.  Isolated tree damage and power outages are possible in this area but not expected to be widespread.

Coastal Impacts:  The main concern is beach erosion, especially along the ocean side of Cape Cod and exposed Island shorelines due to elevated water levels and large waves over at least three high tide cycles.  Pockets of mostly minor coastal flooding are expected around the time of high tide very late this afternoon/early this evening and then again early Monday evening.  The storm surge may peak 2 to 2.5 feet along the Cape and Islands Monday morning but may start to slacken by the time of the early Monday evening high tide.  Waves will continue to build and are expected to approach 20 feet over the waters just off Cape Cod and the Islands and possibly even to 25 feet across the offshore water south of the Islands and Long Island.  Along the Massachusetts east coast, waves will peak to between 12 and 16 feet during Monday.

North of the Cape to Plum Island along the eastern Massachusetts coast, some beach erosion may occur as well as pockets of minor coastal flooding or splashover at the time of high tides through early Monday evening.

Waves and storm surge (along with the amplitude of the astronomical tide) will be on the wane Monday night into Tuesday as the coastal low weakens and pulls off to the east, but there could still be some lingering beach erosion along the Cape and Islands.

Rain:  Rain heavy at times across CT and RI, and southeast MA may accumulate between 1.5 and 2.5 inches with pockets of poor drainage flooding.

Marine:  This coastal storm will continue to 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 through Monday.  Waves will build late tonight and Monday to 15+ 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 at times 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 this early season nor’easter and will update this message if there looks to be a significant change.  If no significant changes to the forecast are anticipated, then this could be the last message on this system as it is now well underway.  For timely weather information on this event, 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 12, 2025 by:
Bob Thompson
Retired National Weather Service Meteorologist
Blue Hill Observatory and Science Center Board member