Marine Interpretation Message
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000
AGNT40 KWNM 181344
MIMATN

.Marine Weather Discussion for N Atlantic Ocean
.NWS Ocean Prediction Center Washington DC
845 AM EST SAT 18 NOV 2017

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

The latest models remained in good agreement across the west
Atlantic through the short term, with both the 06Z GFS and 06Z
NAM consistent with their respective previous runs. The onset of
the southerly gales ahead of the strong cold front still appears
most likely around midnight tonight. In the medium range, versus
its previous runs, the 06Z GFS is first stronger with a
developing surface low forecast to track northeast across the
outer NT2 waters Wed into Wed night, and second is faster and
stronger with a second developing surface low across the waters
Wed night into Thu night. Forecast confidence in the medium
range continues to be below average given the varying model
solutions with these developing surface lows. Will not be making
any significant adjustments to the previous wind grids this
morning.  The slightly higher 00Z ECMWF WAM appears slightly
better initialized than the 06Z Wavewatch III with the west
Atlantic wave heights this morning. A 1245Z Jason-3 altimeter
overpass returned maximum wave heights to 13 ft across the far
northern outer NT2 waters.

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

Summary...Low pressure over the Canadian Maritimes will move E
away from the region as high pressure slides E over the waters
into this afternoon, with conditions improving over the outer
waters. An ASCAT overpass from the last evening indicated gales
to the S and SW of Nova Scotia with these gales moving E of the
offshore waters. The high will move E of the waters later today
with a warm front lifting NE over the New England waters ahead
of a strong cold front. The cold front will push E over the
region Sun followed by strong high pressure building slowly E
from the Midwest and Mississippi River Valley. Widespread gales
are still likely over the waters tonight into early next week,
with storm force winds quite possible over portions of the
northern NT2 waters near the north wall of the gulf stream and
just ahead of the strong cold front Sun. Strong 925 mb winds
near 65 kt are still likely over this region, with an increasing
threat for thunderstorms as well. These thunderstorms may help
to mix these stronger winds downward therefore leading to a good
chance for storm force winds just ahead of the cold front Sun,
especially over the outer northern NT2 zones of ANZ905, 910 and
920. Caution is advised for very gusty winds and very rough seas
in and near any of the stronger thunderstorms that develop ahead
of the cold front on Sun. Otherwise, conditions will be slow to
improve Sun night into Mon night as high pressure slowly builds
E over NT2 into SW NT1 waters. The high will cross the waters
Tue, passing E of the region by Tue night as the next cold front
approaches from the W and NW. This front is still expected to
cross the waters Wed, with low pressure potentially forming on
the front just E of the NT2 waters Wed night as high pressure
builds E toward northern NT2 and NT1 waters.

Forecast confidence...Near to above normal into Tue, then below
normal by Wed and Wed night.

Models...The 00Z model guidance remains in very good agreement
over the region today into Tue evening and we will stay close to
the 00Z GFS and use the smart tool which places the higher first
sigma layer winds over the unstable areas and somewhat lower 10
meter winds over the more stable waters, especially north of the
gulf stream. We will make a few manual adjustments to the
forecast to maintain the previous hazards over the next 48-72
hours. By Wed and Wed night the 00Z models are suggesting a
fairly wide variety of solutions with the 00Z ECMWF continuing
to show a strong low developing and tracking NE over the waters
on Wed, with the 00Z GFS and 00Z UKMET slower with low
development and the low developing E of the waters. The Canadian
GEM guidance is closer to the GFS and UKMET models. The WPC
guidance used an ensemble mean approach to the forecast for Wed
and beyond, and for this package we will trend the wind forecast
from the 00Z GFS for Tue night and Wed, more toward the WPC
forecast for Wed night/Thu.

Seas...As the 00Z ECMWF WAM appears to be initializing a little
better than the 00Z WNA Wavewatch over the waters early this
morning we will start the morning package using a 90 percent WAM
and 10 percent Wavewatch blend, transition to a 50/50 blend of
these two models tonight into Tue, and then something closer to
the Wavewatch thereafter with manual edits to reflect the wind
forecast as described previously.

.EXTRATROPICAL STORM SURGE GUIDANCE...No major changes to the
ESSG appears needed over the next few days as we stay fairly
close to the GFS wind forecast into early next week.

.WARNINGS...Preliminary.

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

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

$$

.Forecaster Clark/Mills. Ocean Prediction Center.



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