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North Atlantic Marine Weather Discussion
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AGNT40 KWNM 201406
Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
1006 AM EDT Sat Oct 20 2018
.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Atlantic Ocean W of 50W from 30N to 50N.
The GOES visible satellite imagery shows low pressure over SE
Canada with a cold front extending to the SW into the Ohio Valley
region. Current surface reports over the offshore waters show
southerly winds ahead of the approaching front with winds up to
25 kt with a few reports up to 30 kt along the coast of Maine.
In addition, there have been reports up to gale force in the
outer NT2 waters, mainly in the unstable environment near the
Gulf Stream. The 06Z GFS and 00Z ECMWF both indicate winds will
continue to increase as low pressure develops along the front as
it moves into the region later today into tonight. The models
support the previous grids which have large areas of gale force
winds today into tonight and a small area of marginal storm
force winds in the outer northern NT2 waters for a brief period
tonight near the developing low. As a result of the model
support, confidence in the previous headlines with this frontal
system is above average, so planning on maintaining previous
headlines while making minimal edits to the grids.
The models continue to differ on the next system on Tue, and the
GFS has been consistently faster than the rest of the guidance as
it also keeps the associated surface low further N as it passes
to the N of the offshore waters. The rest of the 00Z guidance has
trended S with the track of the surface low, while the 00Z ECMWF
remained about 6 hours slower from the 00Z GEM/UKMET and 12 hours
slower than the GFS. The previous forecast continued to favor the
ECMWF solution, so a time shift was used to account for the
slower track of the ECMWF. Since this approach still seems
reasonable, am not planning on making any major changes to the
grids through the medium range period. This includes the warning
headlines on Tue night, so will continue with gales in several of
the northern zones with near average confidence.
A cold front will move east across the waters and winds will
increase ahead of the front with highest winds near the gulf
stream in the short term. GOES 16 RGB Geocolor satellite images
still show mostly clear skies over the waters but clouds are now
entering the offshore waters and that is depicted well on the
current NCEP weather map. The latest Scatterometer pass was about
0240Z and it showed weaker winds over the southern waters. In
addition, the latest buoy and ship observations indicate 30 kt
maximum winds. The latest NCEP weather map has high pressure east
of the central waters and it extends a weakening ridge across
most of the region. Inland frontal boundary now approaching the
mid Atlantic states will move across the waters in the next few
At 500 MB, upper level ridge dominates the forecast waters with
significant energy embedded in an upper level trough now over
the mid west states. The models agree well in the short term on
pushing the energy swiftly across the region. Models just differ
slightly on the timing of the energy as it moves east over the
The latest run of models GFS/UKMETHR/ECMWFHR/CMC have
initialized well the latest synoptic surface observations with
just minor differences on the actual position of the front inland
that is moving east toward the waters and these differences
increase in the short term. Models show enhanced winds near the
gulf stream. GFS is rather fast and has storm force winds just
east of the region while ECMWFHR though slower in moving the
front than GFS, is weaker and does not show any storm force winds
near the waters. For consistency and farther collaboration, will
retain most of the official forecast winds and will stay with
ECMWF in the extended period.
.SEAS...They are initially less than 6 ft over the region are
quickly building to over 6 ft with peaks around 12 ft by the
issuance time. NWW3 and ECMWFWAVE have continued to initialize
well the observed seas pattern and both wave models still agree
well in the short term on swiftly building seas as the front
passes over the waters. Unlike the winds, ECMWFWAVE will build
the seas faster than NWW3 over the northern waters. Since we are
still leaning toward ECMWF for winds, will also continue to use
ECMWFWAVE for seas.
.EXTRATROPICAL STORM SURGE GUIDANCE...There is no indication of
any significant positive surge events over the region for the
next few days.
.NT1 New England Waters...
.ANZ900...Georges Bank east of 68W...
Gale today into tonight.
.NT2 Mid-Atlantic Waters...
.ANZ820...Hudson Canyon to Baltimore Canyon...
.ANZ915...Hudson Canyon to the Great South Channel...
.ANZ920...Baltimore Canyon to the Great South Channel...
Gale today into Sunday.
.ANZ905...The Great South Channel to the Hague Line...
Gale Possible Tuesday night.
.ANZ910...East of the Great South Channel and south of 39N...
Gale Possible Tuesday night.
.ANZ825...Inner Waters from Baltimore Canyon to Cape Charles Light...
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
Gale today into Sunday.
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
.Forecaster Kells/Musonda. Ocean Prediction Center.