North Atlantic Marine Weather Discussion

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AGNT40 KWNM 171926

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
226 PM EST Sat Feb 17 2018

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

Current Conditions...The 12z ncep surface analysis shows a 983 
mb low centered about 300 nm E of Newfoundland, with a strong 
cold front extending SW from the low and across the southern nt2 
waters into the Savannah River region. The analysis shows 
another low centered along the Georgia/South Carolina border, 
which is expected to track NE into the northern nt2 waters 
tonight while strengthening. The analysis also indicated a high 
centered over eastern Pennsylvania, which is current moving E
over the Georges Bank waters. Latest available ascat and ascat 
hi-res passes from a few hours ago show 20 to 25 kt winds along
the eastern edge of the nt1 and northern nt2 waters, and also in
NE flow near the Carolina coast.

Models/Forecast...A developing low will move off the mid Atlantic
coast early tonight, strengthen as it passes NE over the northern
nt2 waters later tonight into early Sun, then move off to the E
later Sun while continuing to strengthen. The nam and medium 
range models are in good overall agreement across the offshore 
waters for tonight and Sun, although the 12z ecmwf looks too slow
in increasing the winds with the developing low, while the 12z
gfs is too shallow with the low's central pressure. The 00z ecmwf
appears to be the most representative and consistent model
solution through Sun, so it will be used for the wind grids over
that timeframe. Otherwise, will stay with the previous wind 
grids for Sun night through the rest of the forecast period in 
order to maintain continuity, which are based mainly on an older
run of the ecwmf, which is favored for the mid to longer range
part of the forecast because the gfs looks overdone with the SW
flow in the nt1 area for Tue through Wed ahead of a cold front. 
The 00z ecmwf and gfs 30m both have storm force winds for early 
Sun, but E of the offshore waters. Most of the medium range 
models show hurricane force winds with the low by late Sun, but 
well E of the offshore waters. Confidence is above average for
the gale warnings and average for the storm warnings.

Seas...The ecmwf wam and wavewatch are in very good agreement 
over the offshore waters for today and tonight, but the ecmwf 
wam has been building up the seas up more quickly in the waters 
just E of the northern nt2 area for Sun, which looks most 
reasonable given that the models all show the developing low 
going into a rapid deepening phase for this timeframe. Will stay 
with the previous wave height grids for the entire forecast
period, which are based on the 00z ecmwf wam, in order to be 
consistent with the preferred 00z ecmwf wind grids.

Extratropical Storm Surge Guidance...N/A.


.NT1 New England Waters...
.ANZ805...Georges Bank west of 68W...
     Gale Sunday.
.ANZ900...Georges Bank east of 68W...
     Gale Sunday.
.ANZ810...South of New England...
     Gale Sunday.

.NT2 Mid-Atlantic Waters...
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale tonight into Sunday. 
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale tonight into Sunday. 
.ANZ905...The Great South Channel to the Hague Line...
     Storm Sunday.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale tonight.
     Storm Sunday.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale tonight.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale tonight.


.Forecaster Scovil. Ocean Prediction Center.