000
AGNT40 KWNM 252055
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
455 PM EDT Tue Sep 25 2018

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

Per the 18Z NCEP surface analysis a strong 1039 mb high, located
over Nova Scotia, extended its ridge down across the NT1 and
northern NT2 waters. A stationary front was located along the
southeast New England coast, adjacent to the inner NT1 waters.
Another stationary front was located along the southeast coast,
adjacent to the inner NT2 waters. A 1016 mb low, being monitored
by the NHC for possible tropical development, was located over
the SE NT2 waters near 33N76W. Numerous thunderstorms associated
with this low were well represented in the latest satellite and
lightning data this afternoon, across mainly the southern half of
the NT2 waters. The latest NHC tropical weather outlook
continues to give this system a 50 percent chance of tropical
development within the next 48 hours and through day 5. It also
continues to mention the system could become a tropical
depression later this afternoon or tonight as it moves
northwestward before increasing upper level wind makes
development unfavorable beginning Wednesday. Mariners should keep
abreast of the latest forecasts. The latest available ASCAT high
resolution data revealed 10-20 kt winds over the southwest NT1
waters with a small area of 25 kt winds in ANZ815 and ANZ810.
20-25 kt winds were noted in the far northeast NT2 waters, while
5-15 kt winds were noted over the inner NT2 waters, with an area
of 20 kt winds noted in ANZ 828, ANZ 830 and ANZ833. ASCAT data
at the time of this MIM wasn`t available in other areas.


Main concern with this forecast update will be the near term in
regards to the aforementioned low pressure over the SE waters and
its forecast movement through the waters into tomorrow, while
monitoring it for aforementioned possible tropical development.
While the 12Z guidance did a good job with initializing the low
this afternoon, the 12Z ECMWF did a slightly better job when
compared to that of the 12Z GFS/UKMET. Guidance moves the low
northward into tomorrow morning, with the low becoming absorbed
by a strong cold front moving off the eastern seaboard by Wednesday
night into Thursday. With the 12Z ECMWF doing a slightly better
job with the initial low position this afternoon and the fact the
12Z run of the ECMWF is similar to it`s 00Z run, which was
favored overnight, felt it was reasonable to allow the ongoing
grids to continue as is but with tweaks made to the grids by
hand where needed through Wednesday night. Hence, will keep
maximum winds at 30 kt across the east quadrant of the low as it
tracks north and northeast across the NT2 waters Wed into Thu.
Additionally will cap winds at 30 kt across parts of the
northern NT2 and south central NT1 waters tonight, and across
the Gulf of Maine tonight into Wednesday morning. Despite no
warnings hazards for sustained winds, winds occasionally
reaching gale force or above in gusts are possible within and in
the vicinity of any areas of thunderstorms.

.SEAS...Buoys from south of Long Island to off the New Jersey and
Delmarva coasts reported 8 to 9 ft wave heights. The 12Z ECMWF
WAM matched fairly well with the ongoing buoy/ship observations
in the offshore waters this afternoon. With the preference to
favor the ongoing 00Z winds grids from overnight, but with some
tweaks by hand where needed, felt it was also reasonable to
continue with the existing wave grids in this forecast.

.EXTRATROPICAL STORM SURGE GUIDANCE...The strong easterly flow
has generated a surge around 1 to 1.5 ft from western Long Island
Sound to along the New Jersey coast, Delaware Bay and the
Delmarva peninsula. The higher ESTOFS appear to have a much
better handle than the ETSS with this surge. Consult coastal
National Weather Services offices for their latest coastal flood
advisory information.

.WARNINGS...Preliminary.

.NT1 New England Waters...
None.

.NT2 Mid-Atlantic Waters...
None.

$$

.Forecaster Holley. Ocean Prediction Center.