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NOAA>NWS>NCEP>OPC>Marine>Atlantic>Offshore>North Atlantic Marine Weather Discussion

North Atlantic Marine Weather Discussion

[Printable Version]   [Alt Link/Previous Versions]   [Glossary]
AGNT40 KWNM 271953
MIMATN

.Marine Weather Discussion for N Atlantic Ocean 
.NWS Ocean Prediction Center Washington DC 
345 PM EDT THU 27 JUL 2017 

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

The 1430Z and 1520Z Ascat overpasses across the western portions 
of the offshore waters returned highest winds to 20 kt off the 
Maine coast, with winds elsewhere 15 kt or less. Over the near 
term the 12Z models are in good agreement across the west 
Atlantic and present no major forecast problems. Both the weak 
high pressure ridge extending northeastward from near Cape 
Hatteras and the weak stationary front across the waters south 
of Cape Hatteras will dissipate tonight. The models are also 
consistent in moving a cold front off the New England coast 
early Friday. The front should stall across the NT1 waters later 
Friday. Over the past several runs, the models have come into 
better agreement with an amplifying upper shortwave which is 
forecast to move southeast across the Great Lakes and through 
the Ohio valley tonight through Friday night before closing off 
near the Mid Atlantic coast Saturday and Saturday night. The 
models have generally trended slower and stronger with this 
system. At the surface, both the 12Z GFS and 12Z ECMWF indicate 
a pair of surface lows will develop with the first moving 
northeast near Georges Bank Saturday night, while the second 
becomes vertically stacked and remains quasi-stationary off the 
mid Atlantic coast late Saturday through Monday. The preferred 
12Z ECMWF is slightly deeper than the 12Z GFS. Also, the latest 
ensemble guidance suggests that the 12Z GFS may retrograde the 
surface low too far southwest Sunday night/Monday. The timing 
differences with how quickly the upper low along the mid 
Atlantic coast will weaken this weekend and eventually lift 
northeast next week have narrowed with the 12Z models. The 12Z 
GFS and 12Z ECMWF are in better agreement with the low position 
Monday night/Tuesday night than they are Sunday/Monday. As for 
the gales, based on slower trend we had previously extended the 
north to northeast gales from south of New England to off the 
Delmarva further out in time (through Monday), and this still 
looks reasonable. So overall the gale hazards will remain mostly 
consistent. By Tue/Tue night, the 12Z models finally show the 
weakening upper low will open into a trough and along with the 
associated surface feature, will lift northeast. 

.Seas...The 12Z Wavewatch III and 12Z ECMWF WAM were about 1 ft 
low near Georges Bank, but otherwise are well initialized across 
the west Atlantic this afternoon. For the forecast wave height 
grids, with the 12Z ECMWF being the basis for the wind grids, 
used a 4:1 12Z ECMWF to 12Z Wavewatch blend through the period. 

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

.WARNINGS...Preliminary. 

.NT1 New England Waters...
.ANZ810...South of New England...
     Gale Saturday.
     Gale Possible Saturday night.
.ANZ815...South of Long Island...
     Gale Saturday.
     Gale Possible Saturday night into Monday. 

.NT2 Mid-Atlantic Waters...
.ANZ820...Hudson Canyon to Baltimore Canyon...
     Gale Saturday.
     Gale Possible Saturday night into Monday. 
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale Possible Sunday into Sunday night. 
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale Saturday.
     Gale Possible Saturday night into Sunday night. 
.ANZ910...East of the Great South Channel and south of 39N...
     Gale Possible Saturday night.
.ANZ825...Inner Waters from Baltimore Canyon to Cape Charles 
Light...
     Gale Possible Saturday night into Sunday night. 
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras 
Canyon...
     Gale Saturday.
     Gale Possible Saturday night into Sunday night. 
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale Saturday.
     Gale Possible Saturday night.

$$ 

.Forecaster Clark. Ocean Prediction Center.


NOAA/ National Weather Service
National Centers for Environmental Prediction
NOAA Center for Weather and Climate Prediction (NCWCP)
Ocean Prediction Center
Mr. Darin Figurskey
Chief, Ocean Forecast Branch
NCWCP, W/NP41
5830 University Research Court
College Park, Maryland 20740-3818

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