AGNT40 KWNM 162031
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
431 PM EDT Tue Oct 16 2018

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

Earlier observations from ASCAT showed a good area of gale-force
winds over the northeast corner of ANZ800 around 1400 UTC.
Observations over the northern Gulf of Maine, even from the
typical higher locations, were well below gale. Primary hazard
for the overnight hours and into early Wednesday will be
isolated-to-scattered thunderstorms along and south of the
surface front which should remain nearly stationary east of the
North Carolina coast.

On Wednesday, the GFS continues with a fairly compact surface low
developing along the surface front early in the day, and moving
east of the offshore waters during the day. The UKMET also has
the low but weaker than the GFS, but the ECMWF has not only
trended toward the GFS but to a similar strength, resulting in a
small area of gales mainly in ANZ925 developing during Wednesday
morning. With deep convection, it is possible for a few gusts
approaching storm force, as winds to 950mb reach at or above 50
knots in the far eastern part of ANZ925 by 15 UTC Wednesday.
As such, for now have added gales for Wednesday only to ANZ925.
Depending on the track of the low it is possible that gale-force
conditions could bleed into the far southern part of ANZ920 where
the zone boundary dives south near the northeast corner of
ANZ925. For now, will leave it out, but could see it added with
subsequent forecast issuances.

The rest of the forecast follows the previous trend, with a broad
area of gales developing over a large part of the offshore waters
from the mid-Atlantic zones northward behind the next cold front.
By the late night hours of Wednesday, gales should be widespread
from ANZ815 to ANZ920 east and northeast. Reviewed model
soundings to assess expansion of the current suite of gales
westward and both the GFS and ECMWF model soundings show a fairly
deep mixed layer west into ANZ815 overnight Wednesday with winds
to around 35 knots all the way aloft to around 850mb, and with a
nearly dry adiabatic lapse rate. As such, confidence currently is
good expanding the breadth of gales as far west as ANZ815 to
ANZ920 overnight Wednesday into Thursday. Gales should depart to
the east of the northern offshore waters early Thursday evening
as strong low pressure over the Canadian Maritimes moves east,
and low 1030s high pressure builds east into the offshore waters.

This next high moves east of the offshore waters Friday into
Saturday ahead of yet another cold front that approaches the
offshore waters from the northwest as yet another low moves over
southeast Canada and into the Canadian Maritimes. Upper
diffluence will be good as the front approaches, and especially
with some areas of deep convection along the front near the Gulf
Stream of the far eastern mid-Atlantic zones, both the GFS and
the ECMWF suggest the possibility of winds approaching storm
force Saturday night especially in ANZ905 and ANZ910. Not
confident enough at this time to introduce winds that strong, but
mariners should keep abreast of the latest forecasts.

In the longer term, both the UKMET and the ECMWF provide for a
developing surface wave along the front that could result in
a period of strong northerly flow gales on the east end of ANZ905
and ANZ910 overnight Sunday. The GFS does not have this wave, but
the possibility that it could be there does have some potential
given the sharper mid-level trough of the ECMWF. This potential
synoptic feature, should it occur, would only extend what should
be gale-force headlines there into Sunday night. High pressure
then builds in over the waters for Monday into Monday night ahead
of what should be another period of unsettled conditions by late
Tuesday.

.SEAS...In the solid cold-air advection, by Thursday afternoon,
expect seas to increase to around 20 feet in the outer mid-
Atlantic offshore zones of ANZ905 and ANZ910. These high seas
should move off to the east by Friday morning. Along and ahead of
the next front, seas should build once again to the upper teens
feet in the outer mid-Atlantic zones Saturday night. In the early
part of the forecast, leaned toward the higher Wavewatch, then
leaned toward the WAM for most of the rest of the period except
Friday night, when the Wavewatch was again a little higher and
preferred.

.EXTRATROPICAL STORM SURGE GUIDANCE...There is the potential for
surge to near one foot off of the far southern South Carolina and
Georgia coasts late Thursday into Friday on both the ETSS and
ESTOFS guidance, with the timing a little later on the latter.
Both the ETSS and ESTOFS show a maximum of negative surge, to up
to around 2 feet on the ESTOFS, from Delmarva to the southern New
England coast Wednesday night. Keep abreast of the latest
forecasts from coastal National Weather Service offices.

.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ800...Gulf of Maine...
Gale Wednesday night into Thursday.
Gale Possible Thursday night.
.ANZ805...Georges Bank west of 68W...
Gale Wednesday night into Thursday.
.ANZ900...Georges Bank east of 68W...
Gale Wednesday night into Thursday.
Gale Possible Thursday night.
Gale Possible Saturday into Saturday night.
.ANZ810...South of New England...
Gale Wednesday night into Thursday.
.ANZ815...South of Long Island...
Gale Wednesday night.

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

$$

.Forecaster Figurskey. Ocean Prediction Center.