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000
AGNT40 KWNM 291159
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
759 AM EDT Sat Apr 29 2017

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

As a cold front approaches from the NW, a moderately strong (up
to 20 or 25 kt) SWly gradient has developed across the
central/Nrn NT2 waters. Max seas over these waters are likely in
the 5-7 ft range, which are being handled fine by the 06Z
Wavewatch III and 00Z ECMWF WAM models at the moment.

Over the short term, overall the latest models share similar
forecast timing for the cold front to move to the New England
coast late today, push SE across the NT1 waters tonight, stall
across the Nrn NT2 waters Sun, then return Nwd as a warm front
Sun night. Overall, the previously populated mix of 00Z GFS winds
still looks representative for the forecast gradients associated
with this fropa (with max winds generally remaining in the 20-25
kt range). So will continue to use these winds for the next
offshore forecast package with just some minor adjustments in
deference to the 06Z GFS and 00Z ECMWF.

In the long range, to slightly differing degrees the latest
models all forecast a strengthening Sly gradient to develop
throughout much of the waters as the warm front continues Nwd
Mon/Mon night followed by the next cold front moving offshore
late Mon night/Tue. With the 06Z GFS remaining consistent, will
continue to use the previously populated 00Z GFS winds for this
strengthening Sly gradient, which overall are supported
reasonably well by the other 00Z global models, and will
continue to forecast possible gales developing across the NT2
waters from the gulf stream Swd Mon night into Tue. So anticipate
making minimal long range changes to the previous offshore
forecasts.



-----------------------------------------------------------------
PREVIOUS DISCUSSION...

Summary...The 00z ncep surface analysis shows a cold front
approaching the new england coast, with a stationary front just
inland of the new jersey coast, and a high pres ridge over most
of the nt2 area. Latest available ascat and ascat hi-res passes
from a few hours ago show 20 to 30 kt winds over the outer zones
of the central and nrn nt2 waters, with 5 to 15 kt winds
indicated over the srn new england waters and near the middle
atlantic coast. Lightning density product data at 0630z shows
a few isolated showers in the nrn and central nt2 waters s and e
of 1000 fathoms.

Models...The 00z medium range models are in good agreement
across the offshore waters regarding the flow pattern and timing
of the main features over the forecast period, except the 00z
ukmet is 3 to 6 hours faster with the warm front for Mon and Mon
night. Also, the models are not in particularly good agreement
concerning the strength of the s to sw flow ahead of the cold
front for Mon night and Tue, with the 00z gem the strongest
solution with max winds of 40 to 45 kt, the 00z ecmwf the weakest
with max winds of 25 to 30 kt, and the 00z gfs/ukmet in between
with max winds of 30 to 35 kt. Since we have had gale warnings up
for the nt2 waters around the gulf stream for a few synoptic
cycles, the 00z gfs 10m/30m solution with the stability smart
tool looks like a very good fit for the wind grids for today
through Wed night. The 00z gfs 10m solution will be used after
Wed night, with the winds capped at 30 kt. Confidence in the gale
warnings is considered to be average to good.

Seas...The 00z wna wavewatch and 00z ecmwf wam both initialized
well versus the latest observations over the offshore waters.
The models are in good overall agreement through the forecast
period, with only minor differences noted. Will use a 50/50 blend
of the 00z wna wavewatch/ecmwf wam for the sea height grids over
the entire forecast period, in order to smooth out the model
differences.

.Extratropical Storm Surge Guidance...N/A.



.WARNINGS...Preliminary.

.NT1 New England Waters...
     None.

.NT2 Mid-Atlantic Waters...
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale Possible Monday night into Tuesday.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale Possible Tuesday.
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Gale Possible Monday night into Tuesday.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale Possible Monday night into Tuesday.
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
     Gale Possible Monday night into Tuesday.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale Possible Monday night into Tuesday.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale Possible Monday night into Tuesday.

$$

.Forecaster Vukits/Scovil. Ocean Prediction Center.


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