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AGNT40 KWNM 040705

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
205 AM EST SUN DEC 4 2016

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

Over the short term...Though it missed the bulk of the
earlier 0141Z high resolution ASCAT-B scatterometer pass
confirmed that gale force winds were present in the strong NW
gradient across the outer nrn NT2 waters. Per a consensus of the
new 00Z models believe this gradient will weaken enough to start
the today forecast period with subgale winds. Otherwise the 00Z
models remain in good agreement that a high pressure ridge will
build offshore today into tonight causing the NW gradient to
continue to gradually weaken with its associated winds diminishing
from W to E. So for this diminishing trend...since the previously
populated 12Z ECMWF boundary layer winds are very similar to those
forecast by the new 00Z GFS/UKMET/ECMWF...see no reason to
repopulate our forecast wind grids for today/tonight.

Then in general the 00Z models agree that a surface low will
develop off the Carolina coasts late tonight...then track ENE
across the central NT2 waters Monday/Monday night. In regards the
forecast track of this system...the 00Z GFS/GEM are both slightly
slower and further S than the 00Z NAM/UKMET/ECMWF solutions. With
the 00Z GEFS mean indicating the 00Z GFS may be too slow...would
favor the other more progressive models. In regards to the
forecast gradients associated with this system...the stronger 00Z
NAM/UKMET/ECMWF and even the weaker 00Z GFS/GEM solutions all to
varying degrees forecast SW gale force boundary layer winds to
develop in advance of its associated cold front. Therefore
forecast confidence in associated gales developing has increased.
So will populate our forecast wind grids with a 50/50 blend of the
00Z ECMWF/UKMET boundary layer winds for Monday/Monday
night...with some additional edits in deference to the 00Z NAM/GFS
which will result in a larger area of associated gales over the
NT2 waters.

In the long range...On Tuesday into Wednesday night...the 00Z
models continue to differ in regards to their exact forecast
tracks and strengths for another developing surface low to form
off the SE coast and then track NE across the NT2 waters. In
regards to the forecast track of this low...the 00Z NAM/GEM look
like fast outlier solutions. Versus its previous 18Z/12Z
runs...the 00Z GFS track is similar but slightly faster. Again the
00Z GEFS mean indicates that the 00Z GFS may be too fast.
Therefore would favor the less progressive 00Z UKMET/ECMWF
forecast tracks which are also somewhat further S than the 00Z
GFS. So will transition to populating with the 00Z ECMWF boundary
layer winds for Tuesday through Wednesday night.

Then further out in the long range...The disparity between the
00Z global models increases significantly Thursday/Thursday
night. The 00Z GFS continues the trend of its previous respective
runs of forecasting a fairly strong surface low to develop near
Cape Cod Thursday afternoon...then pass quickly NE across the NT1
waters later Thursday into Thursday night while pulling a strong
cold front offshore. Again the 00Z GEFS Mean indicates that the
00Z GFS may be too progressive with this system. The 00Z GEM looks
completely out of phase for this system and hence will be
disregarded. The 00Z UKMET and moreso the 00Z ECMWF are slower
than the 00Z GFS in both forecasting an attendant surface low to
develop and track N and NE of the area and then also slower with
their associated cold fropas. For now with very low forecast
confidence will continue to populate with the 00Z ECMWF boundary
layer winds on Thursday/Thursday night...with its winds boosted up
10-15 percent late Thurday night to account for its usual low bias
in cold air advection. So due to the large model disparity will
also cap these winds at below gale force to hold off on
forecasting any possible gale warnings.

Seas...A compromise between the slightly higher 00Z ECMWF WAM and
lower 00Z Wavewatch III would initialized the current seas best.
Since this compromise remains in line with the previously
populated wave grids...which were a 75/25 blend of the 12Z ECMWF
WAM/Wavewatch III...will not repopulate our wave grids for today
and tonight. Then overall since the 00Z ECMWF solution will be
favored...will transition to populating with all 00Z ECMWF WAM
forecast seas for Monday through Thursday night.

.Extratropical storm surge guidance...N/A.


.NT1 New England Waters...

.NT2 Mid-Atlantic Waters...

.ANZ910...East of the Great South Channel and south of 39N...
     Gale Monday night.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale Monday.
     Gale Possible Tuesday night.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale Monday.
     Gale Possible Tuesday.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale Monday.
     Gale Possible Tuesday into Tuesday night.
.ANZ835...Inner Waters from Cape Fear to 31N...
     Gale Possible Tuesday.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Gale Possible Tuesday into Tuesday night.


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