North Atlantic Marine Weather Discussion

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AGNT40 KWNM 200805
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
305 AM EST Wed Feb 20 2019

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

Summary...ASCAT overpasses returned patchy NE Gales just off the
Georgia and S. Carolina coast last evening around 03Z, near the 
developing coastal front. After checking observations it does 
appear that most of the gale force winds occurred in gusts, 
which the nearby coastal WFO forecasts show for their gale 
warnings over these waters, just inside the offshore waters, 
early this morning. The latest observations and nearly all of 
the latest guidance suggests that these winds are beginning to 
diminish. Therefore, for the early morning package we see no 
need to add gales to our inner offshore waters off the SE U.S. 
coast for the morning package. We will indicate sustained winds 
around 30 kt for the far southern zones in the early morning 
package, which is similar to the past few OPC forecasts. Over- 
all, the 00Z guidance remains in generally good agreement over 
the region for the next few days, right into the upcoming 
weekend. Weak low pressure will form along the coastal front 
today and lift N, and then turn E over the New England waters. 
Gales are still forecast to develop early tonight to the S of
the warm front, and ahead of a cold front associated with the 
coastal low. Gales will likely shift E and then NE later tonight
into Thu as the low intensifies as it tracks from around 
Delaware Bay tonight to E of Georges Bank by midday Thu. There
remains the threat for wind gusts exceeding gale force and very
rough seas in and near any thunderstorms that develop later today
and tonight into Thu, mainly from far southern New England waters
southward. Otherwise, there will be an increasing threat for 
gales in the wake of an associated cold front, mainly over the 
outer northern NT2 waters later Thu as the low moves away from 
the area and an associated cold front moves S to the central NT2
waters, with a brief period of moderate cold air advection. The 
front will likely stall over the far southern NT2 waters later 
Thu night into Fri and early Sat, as high pressure builds E and 
SE over NT1 and northern NT2 waters. The front will then return 
N as a warm front later Sat and Sat night with a low forming
near the coast and lifting N and NE with the front. We still
expect gales to develop once again to the S and E of the 
developing low, especially near and S of the N wall of the Gulf 
Stream Sat night. For Sun, we expect the low to lift NE along 
the New England coast, with a strong cold front moving offshore 
by later Sun. Gales will likely expand ahead of the front, 
mainly over NT2 waters during Sun. Strong cold air advection 
will then develop over the waters Sun night as the front crosses
the region, with widespread gales likely over the waters at that
time, with some potential for storm force winds. For now, we 
will cap winds at 35 to 40 kt, and continue to adjust the 
forecast over the next few days. Please monitor the latest OPC 
forecasts for details.

Models...For the early morning package for today into Thu we will
rely on the 00Z GFS and use the smart tool which places the
stronger first sigma layer winds over the unstable areas and
slightly lower 10 meter winds over the stable locations. We will
also blend in some of the higher 00Z Warw winds to maintain the
previous hazards over the waters through Thu. For Thu night into
Sun night we will use a 50/50 blend of the previous grids and 00Z
ECMWF winds, and continue to boost winds up to 10 percent or so,
along with a few manual edits to maintain the previous hazards
over the waters by Sat night through Sun night. Overall, forecast
confidence is slightly above average with the 00Z guidance
remaining quite consistent over the area into the weekend.

Seas...For the early morning package we will use a 50/50 blend of
the previous grids and 00Z ECMWF WAM for today through Sun night,
with a few manual edits in deference to nearby coastal WFO and
TAFB grids and in and near the gale force winds areas. This will
result in no major change from the past few OPC forecasts.
Currently sea heights range from near 12 ft just off the SE U.S.
coast to 2 to 4 ft off the southern New England and northern 
Mid-Atlantic coasts. 

.EXTRATROPICAL STORM SURGE GUIDANCE...The 00Z ESTOFS continues 
to show a positive surge of 1 to 1.5 ft along the SE coast today
with the strong easterly winds near the coast. This seems more 
reasonable than the ETSS which still keeps the positive surge 
values to below 1 ft. A positive surge develops poleward by
tonight into early Thu as the onshore winds increase from the
Mid-Atlantic coast to New England. We prefer the somewhat higher
ESTOFS guidance into Thu, with GFS winds remaining quite
reasonable over the waters during the next day or two. For more 
details please monitor the latest forecast and information from 
your local National Weather Service office. 

.WARNINGS...Preliminary.

.NT1 New England Waters...
.ANZ805...Georges Bank west of 68W...
     Gale Possible Sunday night.
.ANZ900...Georges Bank east of 68W...
     Gale Possible Sunday night.
.ANZ810...South of New England...
     Gale Possible Sunday night.
.ANZ815...South of Long Island...
     Gale Possible Sunday night.

.NT2 Mid-Atlantic Waters...
.ANZ820...Hudson Canyon to Baltimore Canyon...
     Gale Possible Sunday night.
.ANZ915...Hudson Canyon to the Great South Channel...
     Gale Possible Sunday night.
.ANZ920...Baltimore Canyon to the Great South Channel...
     Gale tonight into Thursday. 
     Gale Possible Saturday night into Sunday night. 
.ANZ905...The Great South Channel to the Hague Line...
     Gale Thursday.
     Gale Possible Sunday night.
.ANZ910...East of the Great South Channel and south of 39N...
     Gale tonight into Thursday. 
     Gale Possible Sunday into Sunday night. 
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Gale tonight.
     Gale Possible Sunday into Sunday night. 
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Gale tonight into Thursday. 
     Gale Possible Saturday night into Sunday night. 
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
     Gale tonight.
     Gale Possible Sunday into Sunday night. 
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Gale tonight.
     Gale Possible Sunday.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Gale tonight.
     Gale Possible Sunday into Sunday night. 
.ANZ835...Inner Waters from Cape Fear to 31N...
     Gale Possible Sunday.

$$

.Forecaster Mills. Ocean Prediction Center.