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AGNT40 KWNM 231214

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
714 AM EST MON JAN 23 2017

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

As a warm front drifts N across the central NT2 waters, the front
is combining with a strong high over Quebec to support an Ely
gradient with gale force winds (generally up to 35-40 kt) across
the NW NT2 and SW NT1 waters, while further S Sly gales are also
present across the central/Srn NT2 waters ahead of a cold front
moving offshore near 76W. Max associated seas are in the mid teens
in the Ely gradient N of the warm front which are being handled
better by the higher 00Z ECMWF WAM versus the 06Z Wavewatch III at
the moment.

Over the short term, as one would expect as the event draws nearer
the latest models have overall converged towards a similar
solution that developing triple point surface low (a nor`easter)
will move NE off the N Carolina coast late today, track NNE off
the Nrn mid Atlantic coast tonight (to near 39N73W by 24/12Z),
then track NE across the NT1 waters late Tue/Tue night (to near SW
Nova Scotia by 25/12Z). Overall would favor a compromise 06Z/00Z
GFS and 00Z ECMWF forecast track for this low. In regards to the
associated forecast gradients, with the 06Z GFS remaining
consistent in forecasting an Ely 55-70 kt low level 925 mb jet to
develop immediately N of the associated warm/occluded front by
late today into Tue, continue to have relatively high forecast
confidence in the previously forecasted storm warnings. The only
potential limiting factor though in this storm force Ely gradient
is that the 06Z GFS continues for forecast the lower levels to
become progressively more stable in time. But for now will
maintain the previous forecast continuity and will not be making
any significant changes in the next offshore forecast package
regarding this system.

In the long range, the 06Z/00Z GFS and 00Z ECMWF remain consistent
and in relatively good agreement that the most prominent feature
will be a cold front pushing SE across the waters Thu/Thu night
with gale force associated winds mainly near the gulf stream
across the NT2 waters, followed then by a series of surface trofs
passing SE across the Nrn waters Fri/Fri night. With the 06Z
GFS/00Z ECMWF now forecasting a similar and somewhat stronger WNW
postfrontal gradient, will now repopulate the previous 12Z GFS
first sigma/12Z ECMWF boundary layer wind grids with a blend of
the 06Z GFS first sigma/00Z ECMWF boundary layer wind grids on
late Fri/Fri night. So then will also repopulate our forecast wave
grids with a 50/50 blend of the 06Z Wavewatch III and 00Z ECMWF
WAM seas for the same time period.


A very intense low pressure system will impact the offshore
waters during the next 48 to 60 hours with widespread gale to
storm force winds likely over most of the offshore waters. An
ASCAT overpass from last evening indicate gale force winds
already developing over southern NT2 offshore waters.

Over the short term, there will be no change major changes to the
previous warning headlines. We will closely follow the 00Z GFS
for today through Tuesday night, as it has very good support from
the 00Z ECMWF, 00Z Canadian GEM, 00Z UKMET models. We will also
continue to utilize the smart tool which places the stronger
first sigma layer winds over unstable areas, and slightly lower
10 meter winds over stable waters, through Tuesday night. All
models have generally trended slightly slower, a little further
south, and somewhat deeper regarding low pressure forecast to
track northeast over the far northwest NT2 and NT1 waters over
the next couple of days. We made some manual adjustments to the
grids to be consistent with the previous forecast, and expand the
area of 55 KT winds to include not only southwest NT1 waters from
far northwest NT2 waters as well. There remains some potential
for hurricane force winds over this region by later today. For
now, we will keep these hurricane force winds in gusts, likely
occurring for only a couple of hours later today; and continue to
closely monitor the situation throughout today. The latest
lightning density product, radar, and satellite imagery indicates
thunderstorms, some quite heavy, occurring over mainly southern
NT2 waters, moving east and northeastward. The latest SREF-SPC
thunderstorm guidance indicates locally strong thunderstorms
likely occurring over most of the NT2 waters today, diminishing
tonight. Very gusty winds and very rough seas will be likely in
and near any of the stronger thunderstorms. Conditions will
slowly improve from southwest to northeast over the waters
Tuesday and Tuesday night as the intense low pressure system
lifts northeast toward the Canadian maritimes by later Tuesday

Over the long term, the 00Z global models remain in generally good
agreement over the offshore waters. They are also remaining quite
consistent from their 12Z cycles which were used in the previous
forecast. Therefore, we see no need to alter the previous grids
and forecast from Wednesday through Friday night over the region.
There will be no change to the previous headlines for the long
term part of the forecast, as a result, with a cold front still
forecast to cross the waters Thursday into Thursday night.

.Seas...Per the latest observations and altimeter data it appears
as if both the 00Z Wavewatch III and 00Z ECMWF WAM models have
initialized a little too high, especially over southern NT2
waters early this morning, and a little too low over the Gulf of
Maine. Overall, both models have remained fairly consistent with
their output over the past few cycles. We will therefore, pretty
much leave the previous wave height forecast alone for the early
morning package, and make a few manual adjustments in the grids
to fit current conditions and nearby TAFB and coastal WFO
forecast through the period. Overall, no significant changes
appear necessary from the previous OPC forecast for the early
morning package.

.Extratropical Storm Surge Guidance...A significant surge appears
likely from the Delmarva coast northward today into Tuesday, with
both the 00Z ESTOFS and ETSS models showing surge values up to
around 4 FT between 18Z today and 06Z Tuesday. These values
appear reasonable and could even be slightly too low over the
region; with improving conditions from north to south along the
mid-Atlantic and New England coasts later Tuesday and Tuesday
night as the intense low pressure center finally moves northeast
away from the region, and an offshore flow develops.


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

.NT2 Mid-Atlantic Waters...
.ANZ820...Hudson Canyon to Baltimore Canyon...
     Storm today into tonight.
     Gale Tuesday into Tuesday night.
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale today into Tuesday night.
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale today into Tuesday night.
     Gale Possible Wednesday.
     Gale Possible Thursday.
.ANZ905...The Great South Channel to the Hague Line...
     Gale today into Tuesday.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale today into tonight.
     Gale Tuesday night.
     Gale Possible Wednesday.
     Gale Possible Thursday.
.ANZ825...Inner Waters from Baltimore Canyon to Cape Charles Light...
     Gale today.
     Gale Tuesday into Tuesday night.
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Gale Tuesday into Tuesday night.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale today.
     Gale Tuesday into Tuesday night.
     Gale Possible Thursday.
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
     Gale today.
     Gale Tuesday into Tuesday night.
     Gale Possible Thursday.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale today.
     Gale Possible Thursday.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale today.
     Gale Tuesday into Tuesday night.
     Gale Possible Thursday into Thursday night.
.ANZ835...Inner Waters from Cape Fear to 31N...
     Gale today into tonight.
     Gale Possible Thursday.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale today into Tuesday.
     Gale Possible Thursday.


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