Marine Interpretation Message
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000
AGNT40 KWNM 240736
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
236 AM EST Fri Feb 24 2017

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

Over the short term, the 00Z global models are in very good
agreement and remain quite consistent. The 00Z GFS is in good
agreement with its previous few cycles, and therefore through
the weekend we will remain close to the previous grids and
forecast which will result in essentially no major changes to
the wind forecast and therefore hazards forecast for the early
morning package. The main weather features that will impact
conditions will be low pressure currently centered near 29N 78W
or about 100 NM north of the Bahamas, and then a strong cold
front forecast to cross the offshore waters later Saturday and
Saturday night. A late evening ASCAT pass indicated gales
associated with the low south of the waters, just south of the
far southeastern NT2 waters or zone ANZ935. These gales will
move north into the outer southeast NT2 zones early this
morning, with these gales likely remaining over southeastern NT2
waters today, passing just east of the central and then northern
NT2 waters as the low tracks north and northeast tonight into
Saturday. Gales associated with the strong cold air advection in
the wake of the strong cold front are still set to occur
Saturday night, especially near the Gulf Stream, or over central
NT2 waters as was previously forecast. Gales will also be
possible over the Gulf of Maine offshore waters Sunday into
Sunday night where the strongest pressure gradient will exist
between high pressure building east toward NT2 waters and
rapidly intensifying low pressure lifting north over southeastern
and then eastern Canada. Overall, confidence levels remain above
average through the weekend over the waters.

Over the long term, confidence levels decrease as model variability
increases. From later Sunday night into early Tuesday the 00Z
models are in pretty good agreement, with high pressure crossing
NT2 waters and a weak cold front sliding southeast over eastern
NT1 waters. For this portion of the forecast we will stay close
to the 00Z GFS 10 meter winds. For most of Tuesday and Tuesday
night the 00Z models begin to vary more significantly. The 00Z
ECMWF now brings an intensifying low eastward across NT1 waters
later Tuesday and Tuesday night, which was not forecast by the
12Z ECMWF cycle from yesterday. The 00Z GFS to some degree shows
a weaker low crossing these same waters later Tuesday and
Tuesday night, while the 00Z UKMET and Canadian GEM models do
not indicate the low. For now, we will trend the forecast back
toward the 12Z ECMWF from yesterday for the forecast for most of
Tuesday and Tuesday night in an attempt to maintain forecast
continuity. This idea is also supported by the preliminary
medium range guidance from WPC.

.Seas...Once again early this morning both the 00Z Wavewatch and
ECMWF WAM are initialized within a ft or so of the current
observations over the offshore waters. As we are staying close to
the previous wind grids into Sunday night we will also stay close
to the previous sea heights forecast. From later Sunday night
into early Tuesday we will use a 50/50 blend of the 00Z Wavewatch
and 00Z WAM models, and then fall back to using the 12Z WAM from
yesterday for Tuesday afternoon and night to match the wind
forecast.

.EXTRATROPICAL STORM SURGE GUIDANCE...No major adjustments to the
surge models appear needed through the weekend as we remain
close to the GFS wind forecast over the region for the next few
days.

.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ800...Gulf of Maine...
     Gale Possible Sunday into Sunday night.

.NT2 Mid-Atlantic Waters...
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Gale Saturday night.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale Saturday night.
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
     Gale Saturday night.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale Saturday night.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale today into tonight.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale today.

$$

.Forecaster Mills. Ocean Prediction Center.



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