000
AGNT40 KWNM 302049
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
449 PM EDT Mon Mar 30 2020

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

Over the short term, tonight and Tue, the 12Z models are in very
good agreement. We will populate grids with the 12Z GFS over the
short term, using the higher first sigma layer winds tonight
which initialize closer to the latest ASCAT passes and otherwise
use the smart stability tool, which will place the stronger
first sigma layer winds over the unstable areas, and slightly
lower 10 meter winds in the more stable locations. This will
also help to maintain the patchy gales in the strong E gradient N
of the low passing just S of outer Georges Bank as seen in 18Z
NCEP surface analysis. We will shift the gales a little faster
to the east during Tue with hazards therefore ending over the
offshore waters by 15Z Tue. The latest GOES- Geocolor satellite
imagery and lightning data show thunderstorms occurring ahead of
the low to the E of Georges Bank and NE NT2 waters. Otherwise,
low pressure will drift E away from the waters tonight into Tue
as the associated cold front stalls off the SE coast. The next
significant low pressure system will approach the South Carolina
coast later in the day Tue.

For Tue night into Fri night, across the waters, the 12Z
guidance remains in good agreement overall, with minor
differences in details as one would expect. We will populate
grids with a 2:1 blend of the 00Z GFS first sigma layer winds and
00Z ECMWF winds, and boost winds up to 10 to 15 percent mainly
near the west wall of the gulf stream Tue night into Wed. This
will help to maintain the previous hazards, with storm force
winds possible over the outer southern NT2 zone of ANZ930 later
Tue night into Wed as the intensifying low crosses this area,
with the 00Z guidance in generally good agreement for this outer
zone having the greatest chance for storm force winds Tue night
into Wed. The low is forecast to move from off the South and
North Carolina coast Tue night, to the eastern portion of the
outer southern NT2 zone of ANZ930 by 12Z Wed, and then clear E of
the waters Wed afternoon into Wed night. At the same time, a
weaker secondary low will retrograde towards Georges Bank from
the east. By Thu the secondary low will have dissipated with the
main, intense low, located well E of Georges Bank, or around 40N
58W by 18Z Thu. The low is forecast to stall over this general
area later Thu into Thu night, and then move off to the S and SE
Fri and Fri night, with an expanding large area of N to NE gales
associated with the low overspreading many portions of the New
England and northern Mid-Atlantic offshore waters Thu night into
Fri, with these gales then slowly diminishing from W to E Fri
night as the intense low finally tracks further to the SE away
from the region. Forecast confidence is slightly above average
over the medium range.

.Seas: Both the 00Z Wavewatch and 00Z ECMWF WAM have initialized
up to 1 to 2 ft too low off the southern New England coast per
the latest observations. For the early morning package, we will
use a 2:1 blend of the WAM: Wavewatch guidance for most of the
forecast package, before trending the forecast more toward the
WAM output by Fri night as the Wavewatch may be somewhat overdone
at that time. We will also boost sea heights up to 15 percent or
so near and east of the west wall of the gulf stream by Tue
night into Wed to better match with the enhanced winds forecast
at that time period.

.EXTRATROPICAL STORM SURGE GUIDANCE...We see no need to deviate
significantly from the latest surge guidance over the region for
the next few days, as winds from the GFS guidance appear
reasonable. A modest surge is likely from the Delmarva to
southern New England early today, with a potentially more
significant positive surge developing from the South Carolina
coast to the Delmarva coast Tue night into Wed as an intense low
pressure system tracks E and NE off the SE coast. All coastal
interests should closely follow the latest forecasts and
information issued by the coastal National Weather Service
offices over the next few days.


.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 today into tonight.
Gale Possible Thursday night into Friday night.
.ANZ810...South of New England...
Gale Possible Thursday night into Friday.
.ANZ815...South of Long Island...
Gale Possible Friday.

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

$$

.Forecaster Bancroft. Ocean Prediction Center.