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AGNT40 KWNM 251453
MIMATN

Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
1053 AM EDT Mon Sep 25 2017

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

12Z NCEP preliminary surface analysis still shows Post-Tropical
Cyclone Jose about where it was this time yesterday, about 150 nm
SE of Nantucket, but it has weakened to a spot low embedded in a
weak surface ridge extending SE from a high centered over PA and
NY state. Will drop from the synopsis of the NT2 offshore morning
update.

Otherwise Hurricane Maria was centered just south of the waters
at 30.8N 73.0W at 12Z with maximum sustained winds of 70 kt per
the latest preliminary NHC advisory. Buoy 41002 west of the
cyclone reports N winds of 37 kt with gusts to 49 kt at 14Z,
supporting the ASCAT pass from late last evening showing tropical
storm force winds in the SE NT2 waters. Winds at the buoy have
not increased appreciably over the last several hours as Maria,
centered to the east, has been moving almost straight N. With
the latest advisory track close to and parallel to that of the
06Z GFS, will use as background grids the 06Z GFS 10m winds
except after 18Z Wed time shifted the GFS winds 3 hours slower to
more closely match the NHC track, and then slowed down the GFS
more, by 9 hours by Fri as the GFS has been faster than other
guidance. Will then make edits using TCM wind tool based on the
NHC advisory.

The 12Z sea state analysis and altimeter data indicate observed
seas are within a foot or two of the 00Z/06Z Wavewatch III and
00Z ECMWF WAM. For the morning update, used the previous wave
grids today and then updated with the 06Z Wavewatch III for
tonight and beyond, except time-shifted after 18Z Wed similar to
what was done with the winds.

KEY MESSAGES:

1. Maria is forecast to continue moving northward, paralleling the
U.S. east coast, and it is likely that some direct impacts will
occur along portions of the North Carolina coast beginning Tuesday,
where a Tropical Storm Warning is in effect.

2. Storm surge flooding, especially along the sound side of the
North Carolina Outer Banks, is possible beginning on Tuesday, and a
Storm Surge Watch has been issued for portions of eastern North
Carolina.

3. Swells from Maria are occurring along the coast of the
southeastern United States and will be increasing along the
Mid-Atlantic and southern New England coasts today. These swells
will likely cause dangerous surf and rip currents at beaches in
these areas through much of the week. For more information, please
monitor information from your local National Weather Service office
at www.weather.gov.
-----------------------------------------------------------------
PREVIOUS DISCUSSION...

Note: Warnings below are preliminary, and will be modified based
on the next NHC advisory for Hurricane Maria.

The current GOES-E infrared satellite imagery indicates
Hurricane Maria just S of the NT2 waters moving slowly N towards
the area, and a more compact system in Hurricane Lee well E of
the offshore waters near 50W. Ascat wind retrievals from 0220 UTC
last night indicated tropical storm force winds extending into
the srn NT2 offshore with up to 50 kt in zone ANZ935. Buoy 41002
in the far SE NT2 waters reported 35 kt sustained winds with
gusts up to 41 kt around 0600 UTC. This corresponds well with
the Ascat pass. Also, the 00Z GFS 10m winds and 00Z ECMWF
surface winds are initialized well when compared with the data,
and the models indicate that Maria will move slowly N into Wed
before turning E and passing E of the area Thu and Fri as an
upper level trough steers the system to the E. The 00Z GFS has
trended slightly slower with Maria, but remains faster than the
rest of the 00Z global models. However, the 00Z ECMWF/UKMET/GEM
have all trended faster, but remain slower than the GFS. The
timing and track hinge on the timing of the upper trough moving
in from the NW, and at this am preferring the timing of the 00Z
ECMWF as it trended faster from the previous forecast. For the
wind grids, planning on using previous grids into about 12Z Fri
and modify them with the next NHC advisory. Will then transition
to the 00Z GFS after that time, but will time shift it 12 hours
slower to match the timing of the ECMWF.

.Seas...A 0224 UTC Sentinel altimeter pass indicated seas up to
32 ft to the E of Maria and just S of the offshore waters. The
00Z Wavewatch and ECMWF WAM are initialized within a few ft of
the data, and seem reasonable with moving the seas into the
offshore with the highest winds. However, the 00Z Wavewatch takes
the higher seas off to the east faster than the 00Z ECMWF WAM as
a result of the faster track from the 00Z GFS. For the forecast,
planning on using previous wave height grids to 12Z Fri to remain
consistent with the wind grids, but will adjust based on the next
NHC advisory. Will then populate with the 00Z Wavewatch, but will
time shift it 12 hours slower to match the timing of the 00Z ECMWF
winds.

.Extratropical Storm Surge Guidance...For surge information
related to Maria please see the latest information provided by
NHC and local WFO coastal offices.

KEY MESSAGES:

1. Maria is forecast to continue moving northward, paralleling the
U.S. east coast, and it is likely that some direct impacts will
occur along portions of the coast beginning Tuesday, and a Tropical
Storm Watch has been issued for a portion of the coast of North
Carolina.

2. Storm surge flooding especially along the sound side of the
North Carolina Outer Banks is possible beginning Tuesday, and a
Storm Surge Watch has been issued for a portion of the North
Carolina Outer Banks.

3. Swells from Maria are increasing along the coast of the
southeastern United States and are expected to reach the Mid-
Atlantic coast today. These swells will likely cause dangerous
surf and rip currents at beaches in these areas through much of
the week. For more information, please monitor information from
your local National Weather Service office at www.weather.gov.


.WARNINGS...Preliminary.

.NT1 New England Waters...
     None.

.NT2 Mid-Atlantic Waters...
.ANZ920...Baltimore Canyon to the Great South Channel...
     Tropical Storm Possible Wednesday into Thursday night.
.ANZ910...East of the Great South Channel and south of 39N...
     Tropical Storm Possible Wednesday night into Thursday
       night.
.ANZ825...Inner Waters from Baltimore Canyon to Cape Charles Light...
     Tropical Storm Possible Wednesday into Wednesday night.
.ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light...
     Tropical Storm Tuesday into Tuesday night.
     Tropical Storm Possible Wednesday into Thursday.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
     Tropical Storm tonight into Tuesday.
     Hurricane Tuesday night.
     Tropical Storm Possible Wednesday into Thursday night.
.ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras...
     Tropical Storm tonight into Tuesday night.
     Tropical Storm Possible Wednesday into Thursday.
.ANZ833...Inner Waters from Cape Hatteras to Cape Fear...
     Tropical Storm tonight into Tuesday night.
     Tropical Storm Possible Wednesday into Wednesday night.
.ANZ930...Outer Waters from Hatteras Canyon to Cape Fear...
     Hurricane today into Tuesday night.
     Tropical Storm Possible Wednesday into Thursday.
.ANZ835...Inner Waters from Cape Fear to 31N...
     Tropical Storm tonight into Tuesday night.
.ANZ935...Outer Waters from Cape Fear to 31N...
     Hurricane today into Tuesday.
     Tropical Storm Tuesday night.
     Tropical Storm Possible Wednesday.

$$

.Forecaster Bancroft/Kells. Ocean Prediction Center.



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