What a tough call today for the MA North coast.  We had a prevailing WNW flow much of the day and no model really showed consistency on the amount of flow aloft.   Our questions in these kinds of days are along the lines of how deep will the mixing occur to keep the NW flow going and for how long?   Because, with the cold water temps and solid June sunshine that sea breeze is just waiting to rush ashore.

One of the key stations that typically is one of the first to show the undercut when a sea breeze establishes is our station in Gloucester called Dog Bar Breakwater just inside of Eastern Point Lighthouse.   Check out today’s graph:

dogbar

 

Note the number of times the winds swapped from NW to SE as the 2 forces battled it out.   (note you can use the graph’s zoom function to zoom in to see the details of a day’s winds better).

Did I get the forecast right?  Umm… not as right as I would have wanted.  I did say the Sea Breezes would undercut but they took about 2 hours longer to do it than I put in my tables.   In fact, check out the snapshot for the area at 8:30pm this evening:

830pm

Note that the SE flow solidified and came on fairly strong and is finally filling in north to south.

What do we look for in this kind of situation:   Using our new 1mb pressure plots on our professional viewer we can see the model showing a hint of a surface trough just inside the coast:

front

This subtle little “kink” marked in red usually lets me know that a sea breeze front is likely to occur and this area from Eastern Point down into Nahant is the sweet spot for the sea breeze to initiate.    I’ll also point out that if you just went by the Buoys today and public sensors, you would have thought the sea breezes kicked in much earlier.  Only our WeatherFlow stations showed the persistent offshore flow.

Matt Corey