North Atlantic Marine Weather Discussion

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AGNT40 KWNM 132007

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
407 PM EDT Tue Apr 13 2021

.FORECAST DISCUSSION...Major features/winds/seas/significant 
.weather for the North Atlantic Ocean W of 50W from 30N to 50N.

12z models in good agreement a high pressure ridge builds across
the waters tonight into Wed, then shifts E/SE of the waters 
early Wed night as a triple point low pressure develops near the
New Jersey coast. Models generally remain consistent this low
lifts slowly NE along the coast and into the Gulf of Maine Thu
into Fri night, then slowly moves E of the area Sat and Sat
night. With narrowing solutions among the models, and to wash 
out any major differences among the timing and location of
strongest winds, will run an even blend of the 12z GFS, adjusted
for stability, with the 12z wind-bias corrected ECMWF. This will
maintain gales, but offer a much more conservative forecast with
respect to the duration and spatial coverage of the hazard winds.
By late weekend and into early next week, will trend the grids
toward the GFS as another weak low and front move across the
southern portions, while high pressure settles over the central
and northern areas. Beyond the forecast range, by next Mon into 
Tue, the ECMWF becomes quite the outlier uncorking a rapidly 
intensifying, storm force low across the Mid-Atlantic waters.
This is not supported in ensemble means or other deterministic

Seas: Similar to the winds, will use an even blend of the 
WaveWatch and WAM into Sat, then trend toward the WaveWatch for 
the remainder of the forecast. During the periods of strong
easterly gales across the Gulf of Maine, will run an increase 
in seas up to 20 to 25 percent Friday to yield significant wave
heights up to 15 ft. Even this adjustment is likely too low 
based on the very low bias in wave models in these strong 
easterly wind events. 

Extratropical Storm Surge Guidance: NOAA stations along the Mid-
Atlantic coast continue show water levels 1-1.5 ft above
predictions, fairly close to ongoing guidance from the 12z
ESTOFS. Surge models show these positive values continuing into
Wed night, then possibly increasing Thu night into early Fri
(into the 2 to 3 ft range) along the northern New Jersey coast
through Long Island, highest centered into the NY Bight poleward
of a triple point low developing along the coast. As always,
please monitor products from coastal National Weather Service 
offices for detailed water level information.


.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale Possible Friday.

.NT2 Mid-Atlantic Waters...
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale Possible Friday night.
.ANZ905...The Great South Channel to the Hague Line...
     Gale Possible Friday night.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale Possible Friday night into Saturday. 


.Forecaster Collins. Ocean Prediction Center.