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AGNT40 KWNM 230022

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
822 PM EDT Wed Mar 22 2017

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

Update...The 18z ncep surface analysis shows a 1000 mb low
centered over the bay of fundy, with an associated cold front
extending sw across the nrn and central nt2 waters. The analysis
also shows another cold front extending sw and w over the far srn
nt2 waters. Latest available ascat hi-res and ascat passes from
this morning show 25 to 35 kt winds over the inner zones of the
offshore waters in n to nw flow, with an area of 25 to 30 kt
winds in sw flow ahead of the srn cold front. Lightning density
product data at 2300z shows a line of scattered showers and tstms
ahead of the srn cold front and along the ern edge of the srn nt2

Models...The medium range models are in good overall agreement
across the offshore waters for tonight into fri, so the
representative gfs 10m/30m solution with the stability smart tool
will be used for the wind grids during this timeframe. The gfs is
5 to 10 kt stronger than the other models with the sw flow over
the nt1 and nrn nt2 waters for later fri and fri night, and also
the gfs is faster with the cold front sweeping over the nt1
waters for fri night through sat night. Thus the more
representative ecmwf will be used for late fri through the rest
of the forecast period, although with a small wind boost due to
the low bias of the ecmwf winds. Am not planning to make any
significant changes to the current forecast trend.

Seas...The wna wavewatch builds the seas up more slowly than the
ecmwf wam for this evening into tonight. By late fri into sat the
model differences are relatively minor. Will go with a blend of
the wavewatch/wam with a bias towards the more robust ecmwf wam
for tonight into fri, then use a 50/50 blend of the wavewatch/wam
to resolve the model differences for later fri through the rest
of the forecast period.

Extratropical Storm Surge Guidance...N/A.


There was an ASCAT pass at 15Z which had a swath across the ern
areas of the offshore waters. Cold front that was just moving
offshore at 12Z had moved into the ern areas of the New England
and nrn mid Atlantic waters. Winds were to 35 kt over the Gulf of
ME. Low pressure that moving E over the central into srn mid
Atlantic waters was not evident from the satellite derived wind

Early this afternoon over the central and srn Mid Atlantic scattered
Thunderstorms were in advance of low pressure that was racing E
with its associated cold front. The low pressure should pass E
of the waters in the next several hours with its cold front
passing E and S of the offshore waters. Most of the area of Gales
over the waters this afternoon into tonight should move E of the
waters later tonight into Thu with ern New England into the ern
nrn Mid Atlantic waters ending latest. Will continue to use the
GFS winds and its instability fields for the winds into early Thu
night. Strong High pressure situated inland this afternoon moves
moves into the central mid Atlantic and offshore waters by Thu
night with winds becoming light briefly throughout the waters
through early Friday. By late Friday the GFS/UKMET are showing
winds to up to 30 kt in advance of cold front while the
GEM/ECMWF has about 25 kt in advance of a cold front. Prefer a
weaker solution over the waters initially with models similar
with low pressure tracking N of area with winds strengthening
along or just E of the New England waters into the nrn Mid
Atlantic waters later Fri night/Saturday. The Cold front moves
into the New England waters late Friday night into Saturday...and
slowly moves S into the nrn Mid Atlantic waters late Saturday
and Saturday night as high pressure builds in from the NW. The
ECMWF is slightly slower and weaker than the GFS with moving the
stalled front towards the N in response to upper shortwave. Its
associated surface low moves E into the New England waters
Monday and Monday night. Will continue to use the 12Z ECMWF for
the grids from about Friday afternoon into Mon night with likely
minor adjustments.

Seas...The 12Z wna wave watch is slower with building the seas
than the 12z ecmwf wam this afternoon into tonight. By late
Friday into Saturday differences are not great with approach and
movement of the cold front into the New England waters and then
into the far nrn Mid Atlantic waters late Saturday and Saturday
night. Plan to use a blend with a higher bias towards the ECMWF
wam initially over the 12Z wna and through the remainder of the
forecast period.

.Extratropical Storm Surge Guidance...N/A.


.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale today into tonight.
.ANZ805...Georges Bank west of 68W...
     Gale today into tonight.
.ANZ900...Georges Bank east of 68W...
     Gale today into tonight.
.ANZ810...South of New England...
     Gale today into tonight.
.ANZ815...South of Long Island...
     Gale today.

.NT2 Mid-Atlantic Waters...
.ANZ820...Hudson Canyon to Baltimore Canyon...
     Gale today.
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale today into tonight.
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale today into tonight.
.ANZ905...The Great South Channel to the Hague Line...
     Gale tonight into Thursday.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale today into tonight.
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Gale today.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale today into tonight.
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
     Gale today.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale today.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale today into tonight.
.ANZ835...Inner Waters from Cape Fear to 31N...
     Gale today.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale today.


.Forecaster Scovil/Rowland. Ocean Prediction Center. is the U.S. government's official web portal to all federal, state and local government web resources and services.