Marine Interpretation Message
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000
AGNT40 KWNM 271311
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
911 AM EDT Tue Oct 27 2020

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

The latest model guidance indicates that a high pressure ridge
will build across the offshore waters today into Wednesday and
then begin to weaken. A cold front will then move across the nt1
waters Wednesday night. Extratropical Zeta will then move into
the northern nt2 waters by late Thursday with gale conditions
associated with it. This low will move east of the offshore
waters by Friday while another trailing low crosses the northern
nt2 waters with gale force winds. Conditions will then diminish
across most of the offshore waters Friday night and Saturday as
high pressure builds across the north portion. A cold front will
then approach the offshore waters from the west on Sunday. For
wind grids will continue to use the current grids throughout the
forecast period. Current warnings look reasonable and few changes
should be needed on the next offshore waters forecast.

For wave height grids will also continue to use the current grids
throughout the forecast period.

.EXTRATROPICAL STORM SURGE GUIDANCE...The 06Z ESTOFS and ETSS
show no significane positive surge through Thu but positive surge
up to 1 ft along the Mid-Atlantic and New England coast by Fri
in the strong easterly flow behind the front over the N NT2
waters. Consult your local National Weather Service coastal
office for more detailed information.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

Main concern of the forecast will be the impacts of T.C. Zeta
over the OPC offshore waters as it moves into and through the N.
Mid- Atlantic and southern New England waters Thu night through
Fri night. The latest forecast incorporates the latest advisory
information from the 09Z National Hurricane Center on what is now
Tropical Storm Zeta. Right now Zeta is expected to re-intensify
to a hurricane in the Gulf of Mexico before weakening inland over
the SE states and then become a post-tropical cyclone by 06Z Fri
as it moves off the Delmarva coast and skirts the southern
portion of Georges Bank by Fri 18z. Among the guidance the 00Z
GFS time shifted 3 hrs slower has the best fit concerning the
track of Zeta Thu into Thu night before it moves offshore. Then
as model spread increases Thu night through Fri night an even
blend of the 00Z GFS (3 hrs slower) with the 00Z ECMWF through
Fri followed by a blend of the previous grids with the 00Z
Canadian through Sat are preferred. The GFS becomes more
suppressed and faster later Fri into Sat versus other global
models. In spite of model spread all of the global guidance is
in agreement that a decent area of gale force winds associated
with what will be Post-Tropical Cyclone Zeta and a developing
cold front with the low. These gales cover the New England, Mid-
Atlantic and parts of the SE U.S. waters. While the general
onset the of the gales hasn`t changed, beginning by 00Z Fri and
lasting through Fri night, I have mostly maintained spatial
coverage per the aforementioned adjusted GFS and model blends
with the ECMWF/Canadian suggesting a decent area of gale
coverage. Additionally the global guidance is become more
bullish with the 00z ECMWF/CMC/GFS being quite bullish and
suggesting storm force winds over the outer Mid-Atlantic waters
in the vicinity of the Gulf Stream and 45 kt Gulf of Maine for a
time on Fri onto Fri night. The 00Z GFS suggests storm force
winds over the northern and central Mid- Atlantic waters near
the Gulf Stream mainly Thu night due to its faster timing.

High pressure then moves across the waters Sat and Sat night
with the model preference shifting toward the 00Z ECMWF late Sat
and beyond, also in line with WPC medium range guidfance.

With the above noted, I didn`t feel confident enough to go storm
force as there still enough uncertainty to hold off on that, but
I do carry winds up to 45 kt over the Mid-Atlantic waters near
the Gulf Stream later Thu night through Fri. While confidence
concerning gales is above average, adjustments to the duration
and spatial coverage of gales are likely in the forecast through
the week. Mariners should continue to closely monitor forecasts
from OPC and the National Hurricane Center through the week.

.SEAS...I used the 00Z WNA Wavewatch through Tue night
followed by a 1:1 blend of the 00Z Wavewatch and 00Z ECMWF WAM
through Wed night. After that the 00Z a 1:1 blend of the 00Z
Wavewatch (time shifted 3 hr slower is used through 03Z Fri
follwed by a 1:1 blend of the time shifted Wavewatch with the
00Z ECMWF WAM through Fri and then a 1:1 blend of the 00Z
Canadian and the previous grids through Sat, consistent with the
winds. Then model prefernce shifts to the 00Z WAM Sat night as
is the case with the winds.


.WARNINGS...Preliminary.

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

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

$$

.Forecaster Nolt/Bancroft. Ocean Prediction Center.



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