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AGNT40 KWNM 230113
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
813 PM EST Wed Feb 22 2017

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

Little change appears needed to the previous forecast for the
evening update. High pressure is crossing the waters early
tonight, and will move well east of the waters, or about 200 NM
northeast of Bermuda, by tomorrow evening. Low pressure
currently over Florida is still forecast to impact the waters
tomorrow into the weekend with a strong cold front sliding east
and southeast over the area later Saturday and Saturday night.
No change to the previous headlines appears needed at this time
as well, with the 18Z GFS is good agreement with the 12Z cycle
into the weekend.

Seas...Sea heights range from around 7 feet over northeast and
far southwest NT2 waters, to 3 ft or so closer to the coastal
waters from North Carolina northward per the latest observations
and RA1 OPC sea state analysis. Again, no major changes are
anticipated for the evening update. We will tweak the previous
grids somewhat to fit current conditions and nearby coastal WFO
and TAFB forecasts prior to forecast issuance.

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PREVIOUS DISCUSSION...

The latest NCEP surface analysis and GOES visible satellite
imagery indicate low pres over the NE Gulf of Mexico, and high
pressure across the central NT2 offshore waters. The 12Z
GFS/ECMWF/ UKMET/GEM all indicate the low over the Gulf of Mexico
will move slowly east to the south of the waters over the next
couple of days, then turn NE while accelerating as a strong upper
trough moves into the wrn Atlc and absorbs the system Sat into
Sun. Ascat wind retrievals indicate 25 in the far SW NT2 offshore
waters, and current surface observations along the SE coast
indicate about the same. The 12Z GFS winds are initialized well
when compared with the data, and indicates the winds will slowly
increase as the low moves closer to the offshore waters and
interacts with the high over the area. The rest of the 12Z models
agree fairly well with the GFS on the overall pattern, and also
on the track of the low. The GFS indicates gales over srn NT2
with this low by Fri, and the 12Z NAM/GEM agree fairly well. The
12Z ECMWF/UKMET are both weaker with the winds despite having the
same pressure gradient. However, with the low wind bias of the
ECMWF/UKMET and the models indicating negative static stability
over the Gulf Stream, deeper low level mixing can be expected.
The GFS/ECMWF are both indicating near 50 kt over srn NT2 by Fri,
so confidence in the previous gale warning is above average. As
a result, planning on continuing previous headlines with this
low. Will also start out with the GFS as it has been consistent
in the short range and agrees well with the rest of the 12Z
guidance.

As the low starts accelerating to the north, the GFS has trended
faster and is now faster than the rest of the models with this
low on Sat into Sun. The 00Z ECMWF had been faster, but has
trended slower trended slower in the 12Z run and agrees well now
with the timing of the 12Z UKMET/GEM solutions. The GFS is also a
little faster with the cold front, so favoring the 12Z ECMWF
timing as it is supported better by the rest of the 12Z
guidance. As far as the intensity is concerned, the 12Z
GFS/ECMWF/UKMET/GEM all show strong cold advection across the nrn
offshore waters behind the front. The models also show negative
static stability in the cold advection, so expecting low level
mixing. The previous forecast had gales for Sat into Sun. The
ECMWF is indicating winds up to 30 kt, and the 12Z GFS indicates
gales. Confidence is about average with this round of gales, so
planning on continuing previous warnings for the next forecast.
Will populate with the 12Z ECMWF from 00Z Sun onward, but will
boost winds to account for the low bias. Otherwise, will stay
with the 12Z ECMWF for the remainder of the forecast period.

.Seas...The 12Z Wavewatch and ECMWF WAM are initialized within a
ft or two of the current data in the wrn Atlc. The models agree
fairly well throughout the forecast period, so planning on using
a 50/50 blend of the two solutions as a compromise to the minor
differences.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.


.WARNINGS...Preliminary.

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

.NT2 Mid-Atlantic Waters...
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale Possible Sunday.
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale Possible Saturday.
     Gale Possible Sunday.
.ANZ905...The Great South Channel to the Hague Line...
     Gale Possible Sunday into Sunday night.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale Possible Saturday.
     Gale Possible Sunday into Sunday night.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale Friday.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale Thursday night into Friday.

$$

.Forecaster Mills/Kells. Ocean Prediction Center.



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