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000
AGNT40 KWNM 211348
MIMATN

.Marine Weather Discussion for N Atlantic Ocean
.NWS Ocean Prediction Center Washington DC
850 AM EST TUE 21 NOV 2017

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

The latest runs of the GFS and ECMWF share a similar timing and
strength with the developing surface low expected to track
northeast across the outer NT2 zones tonight through Wed
evening. However, the GFS continues to be slightly further east
with the track of the low, and consequently, the strongest
associated winds are along or just east of the outer northern
NT2 waters late Wed into Wed night. The latest GEFS and ECMWF
EPS support their respective GFS and ECMWF deterministic runs.
Will maintain the previous wind and hazard grids with this
morning updates. We have well above average forecast confidence
that warnings will be limited to the outer zones, well east from
any Mid Atlantic coastal zones. Versus yesterdays runs, the 00Z
GFS was then stronger with the next developing low across the
southern NT2 waters Thu/Thu night, and even indicated some
associated gales. The 06Z GFS came in slightly weaker, and OPC
preference will continue with the 00Z ECMWF through the end of
the week. The NOAA buoy 44011 near Georges Bank reported 11 ft
at 13Z, which is still a couple feet higher than the 06Z
Wavewatch III. The slightly higher 00Z ECMWF is better
initialized with the wave heights this morning.

---------------------------------------------------------------
...Previous Discussion...

There was an ASCAT pass at 01Z which had a swath across the
eastern areas of the New England waters into the northern areas
of the mid Atlc waters E of 72W. There was an abundant area of
gales E of roughly 70W with NW winds to 35 kt. Elsewhere winds
were to 30 kt across much of the remainder of the swath. A later
pass from ASCATB at 02Z had a swath E of 70W where winds were to
35 kt across a smaller area with the much of the remainder of
the region showing 30 kt. The area of gales should shift E of
the area within the next several hours as the high pressure
ridge and its surface high moves further offshore this morning.

By later tonight into Wed a mid to upper level vorticity max
moves off the northeast Florida coast in response to an
amplifying upper level shortwave moving towards the E coast. The
00Z GFS/ECMWF continue to depict a vigorous developing surface
low moving NE over the srn mid Atlantic waters by late
tonight/early Wed and then moving rapidly over the outer waters
of the central and northern mid Atlantic areas Wed while
strengthening and passing quickly NE of the area by Wed night.
Models still are showing storm force winds developing over the
outer waters Wed. The GFS is faster with developing the storm
force winds Wed. These models are in better agreement with the
exact track and timing of the developing low than has been the
case, although there some differences with areas of highest
winds. The GEM/UKMET are also showing the developing low moving
on a similar track although slower than the GFS/ECMWF. Still
prefer the ECMWF overall which seems to be the most consistent
with the developing low and will favor its area of strongest
winds which develop over the outer waters. By late Thu and Thu
night another mid to upper level vorticity max moves over the
Gulf states with a surface low moving across FL. The models are
continuing to show differences with the timing and the track of
the surface low. Will use the ECMWF solution for this event and
am reluctant to go any stronger than 30 kt for now. The UKMET is
further W and slower than the ECMWF in moving the low pres away
from the waters while the GFS is slightly faster than the ECMWF.

Seas...Will favor the ECMWF wam through much of the forecast
period with the exception of today where a 50/50 blend of the
WWIII and ECMWF wam will be used.

.EXTRATROPICAL STORM SURGE GUIDANCE...n/a.

.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ900...Georges Bank east of 68W...
     Gale Wednesday night.

.NT2 Mid-Atlantic Waters...
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale Wednesday.
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale Wednesday.
.ANZ905...The Great South Channel to the Hague Line...
     Gale Wednesday.
     Storm Wednesday night.
.ANZ910...East of the Great South Channel and south of 39N...
     Storm Wednesday.
     Gale Wednesday night.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras
Canyon...
     Gale Wednesday.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale Wednesday.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale tonight.

$$

.Forecaster Clark/Rowland. Ocean Prediction Center.



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