Marine Interpretation Message
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822
AGNT40 KWNM 210803
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
303 AM EST SAT JAN 21 2017

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

The main weather feature that will bring deteriorating and
hazardous conditions to the offshore waters over the next few
days will be low pressure forecast to intensify as it moves just
off the middle Atlantic coast Monday, and then tracks northeast
near or just off the New England coast Monday night into Tuesday
night. It now appears that storm force winds will become possible
over most of the NT1 offshore waters later Monday into Monday
night with a strong low level jet in place, and widespread gales
elsewhere from Sunday night into Tuesday. Scattered thunderstorms
are possible as well with this low and associated frontal
systems, with locally very gusty winds and rough seas in or near
any thunderstorms that occur, mainly over southern and central
NT2 offshore waters over the next few days.

Over the short term, the 00Z models are in very good agreement.
Weak low pressure located about 130 NM east of Cape Hatteras
early this morning will move east, and pass east of the central
NT2 waters by this afternoon. A 2033Z ASCAT pass indicated
maximum winds near 25 KT associated with this low last evening. A
weak high pressure ridge over NT1 waters will also move east away
from the waters today. Another weak low will move east along a
developing warm front near VA Beach on Sunday, with the main low
that will bring gale to storm force winds to the waters located
over the lower Mississippi valley. The weak low is forecast to
dissipate as it moves east and northeast along the front Sunday
night. The main low will move east and reach a position near the
Delmarva coast later Monday, with the warm front lifting north to
near 40N. For the short term part of the forecast we will stay
close to the 00Z GFS guidance and continue to use the tool which
places the stronger first sigma layer winds over unstable areas,
and somewhat lower 10 meter winds over stable areas. Overall,
there are no major changes from the past few OPC forecast over
the short term, with confidence in the forecast at near to above
normal levels.

Over the long term, we have decide to go ahead and add storm force
winds possible to most of the NT1 offshore waters later Monday
and Monday night. Elsewhere, widespread gale force winds are
possible later Monday into Tuesday. The 00Z GFS is now a little
deeper with the low as it moves into the region later Monday into
Tuesday, and is in very good agreement with the 00Z ECMWF and 00Z
UKMET guidance. As a result, we will continue to use the tool
which places the strongest winds over unstable areas as noted
previously, for the period later Monday through Tuesday night.
Improving conditions are forecast from southwest to northeast
over the waters Tuesday into Wednesday as the low moves from near
the New England coast to the Canadian Maritimes. For Wednesday
and Wednesday night we will use a 50-50 blend of the 00Z GFS and
00Z ECMWF, as some model differences develop regarding the timing
and strength of the cold front forecast to impact the region
around the middle of the upcoming week. Confidence levels are
near average through Tuesday night over the waters, and then near
to below average thereafter.

.Seas...Both the 00Z Wavewatch III and ECMWF WAM models have
initialized the current seas well, per the latest observations
and altimeter data. As their wind forecasts are similar over the
next few days we will use a 50/50 blend of these two wave models
throughout the forecast.

.Extratropical Storm Surge Guidance...In the strong Ely gradient
forecast to develop N of the front Sun night into Tue the 00Z
ESTOFS continues to forecast a slightly more significant surge
(up to 3-5 FT) to develop Northward up the coast from Delaware to
the southwestern New England than forecast by the 00Z ETSS. Would
recommend favoring the higher 00Z ESTOFS solution for this event.

.WARNINGS...Preliminary.

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

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

$$

.Forecaster Mills. Ocean Prediction Center.



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