September 18, 2010 - With two active hurricanes and more tropical activity on the way the Atlantic ocean has been an active place and will get more active during the coming week. The forecast chart above from the US Navy (FNMOC) for this coming Wednesday 9/22 shows a tremendous amount of motion in the ocean. Dark blue corresponds to flat water, lime green to 5' seas, yellow to 10' seas...dark brown means 42' plus seas. Wednesday is after the peak swell from Igor has passed Cape Cod. The biggest waves from Igor will be hitting the National Seashore beaches on Tuesday morning with faces of 10-12 maybe even 15 feet. 

And you thought the ocean was blue...

September 3, 2010 - The biggest waves from Earl will be hitting south facing beaches on Nantucket and Martha's Vineyard. Below is a live cam operated by WHOI (updates every 20 minutes) that overlooks South Beach (aka Katama) on MVY. Reported wave height at 4:50 pm at South Beach is 11.2 feet:

September 3, 2010 

8:00 am - Earl has shifted east and forecasts for winds and waves are somewhat reduced. South of Nantucket the biggest waves are now expected to reach 16' and the odds of sustained hurricane force winds of 75+ mph across the Lower Cape are now 30%. The storm remains powerful and a Hurricane Warning is still in effect.

September 2, 2010

6:00 pm - When forecasting the arrival of a storm path that's a 1000 miles away a tiny variation can mean the difference between a direct hit and a 50 mile miss.  As things look now, for much of the Cape, Earl will have about the same impact as a typical nor'easter. The exception may be properties along Nantucket Sound where uncommonly large seas could wash ashore.

12:30 pm - Things have gone downhill since early this morning. In the 11 am forecast the path shifted west and now moves directly over Nantucket and the lower Cape. Click on the graphic for a larger image.

8 am - This morning's Hurricane Center forecast shows a capital "H" on top of Orleans. There is talk of wind gusts reaching 90 mph on Nantucket and 75 mph on Cape Cod. If Earl follows the Hurricane Center's currently forecast path those numbers are probably on the low side. Peak wind will be late Friday night.

From a surf perspective Friday will be a mess from onshore winds but Saturday should be clean, starting at well over 2X overhead from SE around sunrise and dropping quickly to head high from S by sunset.  The wind will be blowing hard offshore from the west.

Earl is moving quickly so damage from sustained high winds should be minimized and (unfortunately) the window for overhead waves is small.

September 2, 2010 - See updated wave height forecasts from NWS Boston here.

September 1, 2010 - Courtesy of NWS Boston here's a graphical forecast from this morning of wave heights expected to arrive in our region from Hurricane Earl at 5 pm Friday, 2 am Saturday and 8 am Saturday. Max wave height is late Friday night/early Saturday morning with wave heights dropping quickly by 8 am Saturday.  The graph shows 9' waves coming into Nantucket Sound. Will head high waves hit the beaches? 

Beaches around Bass River to the east of Hyannis are open to seas coming in from the south from the channel between Martha's Vineyard and Nantucket and from the southeast from the slot between Monomoy and Nantucket.

High tide is between 7-8pm. The biggest waves are forecast to arrive 6 hours later around the time of low tide - this makes head high waves unlikely - good news for marinas and waterfront property owners.

As for the Atlantic Coast and Cape Cod National Seashore - the wave energy is coming straight out of the south so the waves that will hit the regular surfing beaches will likely stay between 1X-2X head high.