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000
AGNT40 KWNM 271905
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
205 PM EST Mon Feb 27 2017

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

Over the short term, as a weak cold front approaches from the NW,
pretty much as expected latest observations show winds are
gusting to gale force in the WFO Caribou coastal waters. With the
12Z GFS showing increasing low level stability developing,
expect this gradient to weaken below gale force by the start of
the TONIGHT forecast period, and then weaken further later
tonight as the front drifts offshore into the Gulf of Maine and
weakens. Then with only small timing differences, the 12Z models
all forecast a warm front to develop off the Nrn mid Atlantic
coast Tue and then lift NNE across the NT1 waters Tue night with
a strengthening SSW gradient developing throughout much of the
waters. Then the 12Z models all forecast the SSW gradient to
strengthen further in response to a strong cold front approaching
from the W Wed and then pushing offshore Wed night. With the 12Z
GFS remaining consistent in forecasting a 60-75 kt 925 mb SSW
jet to develop in advance of this cold front, remain highly
confident that widespread SW gales will develop throughout the
NT1 and Nrn/central NT2 waters Wed/Wed night. In fact, with this
jet in place the 12Z NAM/GFS now forecast storm force SW first
sigma level winds to develop for a brief period of time late
Mon/Early Tue across the outer central NT2 waters. With these
winds being in the proximity of the gulf stream, and with the
usually conservative 12Z UKMET/ECMWF also forecasting 35-45 kt
boundary layer (BL) winds, will now go ahead and add storm
warnings for these waters then. So plan on populating our
forecast winds with our smart tool that will place the
representative and stronger 12Z GFS first sigma level winds in
unstable areas and weaker 12Z GFS 10m winds in stable areas for
tonight through Wed night.

In the long range, in the wake of the cold front Thu/Thu night to
better account for the strong cold air advection forecasted,
will populate with primarily the stronger 12Z GFS first sigma
level winds with some additional minor edits in deference to the
12Z ECMWF, which are supported well by the 12Z NAM/UKMET and will
support WNW gales across the NT1 and Nrn/central Thu into early
Thu night.

Then further out in the long range, the 12Z GFS continues its
previous model trends of forecasting a vigorous clipper-type
surface low to race E near 40N Fri into Fri night with widespread
associated gale force BL winds. Though there is an absence of
associated individual ensemble members, the 12Z GEFS Mean
indicates that the 12Z GFS is perhaps too strong with this
feature. The 12Z UKMET though has now trended towards this
stronger GFS solution, but is slightly less progressive. The 12Z
GEM forecasts no surface low at all, but does forecast a surface
trough passage with an associated gale force NWly gradient
developing late Fri/Fri night. The 12Z ECMWF supported the
forecasting timing of the 12Z GFS for this system, but forecasts
a significantly weaker low. solution on Thu night into Fri night,
though will beef up the 00Z ECMWF winds somewhat Fri night in
the cold air advection it forecasts to develop in the wake of its
weaker surface low. Believe the 12Z ECMWF is likely too weak
with this system and the 12Z is likely too strong. Therefore
would go with a compromise between the 12Z GFS/ECMWF and so will
populate with a 50/50 blend of the 12Z GFS first sigma/10m and
12Z ECMWF BL winds for Fri through Sat night.

.SEAS...The 12Z Wavewatch and 12Z ECMWF WAM have both initialized
the current seas equally well. With their associated 12Z
GFS/ECMWF solutions being similar tonight through Thu night, and
then since a compromise 12Z GFS/ECMWF solution will be favored
Fri through Sat night, will populate our forecast wave grids with
a 50/50 blend of the 12Z Wavewatch and 12Z ECMWF WAM for tonight
through Sat night.

.EXTRATROPICAL STORM SURGE GUIDANCE...In the strong offshore
postfrontal gradient forecast to develop Wed night into Thu
night, the 12Z ESTOFS forecasts a more significant negative surge
to develop along the coast from the Virginia Capes Nwd than
forecast by the 12Z ETSS. Would favor the more conservative 12Z
ETSS for this surge

.WARNINGS...Preliminary.

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

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

$$

.Forecaster Vukits. Ocean Prediction Center.



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