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AGXX40 KNHC 301021 AAA
MIMATS

Marine Weather Discussion...UPDATED
NWS National Hurricane Center Miami FL
621 AM EDT Thu Mar 30 2017

...updated for weather in Gulf of Mexico...

Marine Weather Discussion for the Gulf of Mexico, Caribbean Sea,
and Tropical North Atlantic from 07N to 19N between 55W and 64W
and the Southwest North Atlantic including the Bahamas

...GULF OF MEXICO...

The gradient associated with weak high pressure that extends
from the Western Atlantic to the central gulf is allowing for
light to moderate east to southeast winds over the eastern gulf
waters. Over the central gulf, southeast winds have increased
since yesterday to fresh to strong as the pressure gradient
between the ridge and a cold front just inland the Texas coast
has tightened. The cold front is preceded by a trough that
extends from near Lake Charles Louisiana to near 27N96W. Latest
satellite imagery and current NWS radar imagery shows a quite an
impressive developing line of numerous strong thunderstorms
along and within 50 nm east of the trough containing numerous
lightining strikes. Some of this activity might reach the strong
to severe limits later today as it translates eastward across the
waters mainly north of about 27N.

The cold front will move off the coast around 09Z this morning,
and quickly move across the northwest waters through this
morning, the central waters this afternoon and the eastern
waters late tonight through while weakening. Before the front
weakens, fresh to strong southerly winds will precede the front
mainly over the far northern waters today while the same type of
winds over the central waters as stated earlier diminish to
moderate winds. The gradient associated with a thermal trough has
brought an increase to southeast winds over the eastern Bay of
Campeche, and waters just northwest of the Yucatan Peninsula.
These winds will diminish late this morning. This process of the
thermal trough with increasing southeast winds will repeat each
night through Saturday night.

Otherwise, plenty of atmospheric instability associated with
upper level dynamics is expected to bring numerous showers and
thunderstorms, some capable of producing strong gusty winds
and tough seas, ahead of the front through Friday. Another area
of low pressure will develop over the southern Plains Friday,
and move over the southern United States during Saturday
through Sunday period. The pressure gradient between the low and
Atlantic high pressure ridging extending to the eastern waters
will once again bring an increase to southeast winds over much
of the central and western gulf. These winds are forecast to
increase to mainly the strong category with seas around 8 or 9 ft
during the upcoming weekend. The cold front associated with this
next round of low pressure is forecast to move off the Texas
coast on Sunday night. This front will also quickly move across
the basin reaching from near the far western Florida panhandle to
the eastern Bay of Campeche early on Monday, and from near west-
central Florida to the northeast Yucatan Peninsula by late on
Monday. Mostly strong southerly winds are likely to precede the
front, with a good possibility of a squall line developing out
ahead of it. There is a chance for southerly winds to near gale
force over some portions of the north-central waters on Monday.
Scattered showers and thunderstorms with strong gusty winds and
frequent lightning are very possible along the front or squall
line.

...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N
BETWEEN 55W AND 64W...

Gentle to moderate trades continue over the Caribbean due to the
continuation of a weak pressure pattern. However, high pressure
building over the SW N Atlc will allow for the trades to
become fresh at night mainly over the central and south-central
Caribbean while fresh to strong winds are forecast for the Gulf
of Honduras and along the coast of Colombia at night. This
pattern of moderate to fresh trades over the majority of the
Caribbean and fresh to strong winds over the Gulf of Honduras
and Colombia coast will persist through the upcoming weekend.
Over the tropical Atlantic waters, a weakening cold front is
analyzed from near 22N55W southwest to the vicinity of the
Leeward Islands. A very weak pressure gradient south of the front
is sustaining gentle to light easterly flow over just about the
entire Tropical North Atlantic zones, except for moderate trades
in the southeast portion of these zones. The front is forecast to
continue to slowly move southeastward while gradually
dissipating through Friday as it loses its upper support.

Northerly swell is decaying in the Tropical North Atlantic,
however wave model guidance is suggesting that quite an
impressive and extensive batch of long period northerly
swell will begin to infiltrate the Tropical North Atlantic
waters starting on Saturday. This northerly swell will
propagate through all of the Tropical North Atlantic zones
into Monday while inducing combined sea state of 8-11 ft. By
late on Monday, the bulk of the swell energy will be confined to
south of about 16N, with combined sea state of around 8-10 ft.

...SW N ATLANTIC INCLUDING THE BAHAMAS...

...A very progressive pattern in play going into early April...

The northeast swell in the eastern portion of zone AMZ115 has
subsided to 5-7 ft. This respite will be short-lived as yet
another set of long-period northerly swell will move into the
northeast portion of zone AMZ115 beginning this evening, with
seas of 6-9 ft. This swell will propagate through all of the
eastern portion of the basin into Sunday night, with combined
sea state peaking to around 10 ft before subsiding to 8 ft on
Sunday and further to 7 ft on Monday. Weak high pressure remains
over the basin as a rather weak cold front has moved into the
far northern waters from near 31N66W to 29N75W and stationary
northwest to the coast of the northeast Georgia. The front is
followed by generally fresh northwest to north winds, while
moderate to locally fresh northeast to east winds are north
of the stationary front. The cold front will move southeast of
the zones AMZ115 and ANZ121 tonight, while the stationary
front becomes diffuse. Its remnants will lift northward as a
warm front through Friday. This will take place as a cold front
advances across the southeast U.S. This next cold front will
emerge off the southeast U.S. coast on Friday evening. The front
will begin to push the aforementioned high pressure over the
western part of the basin eastward as it progress over the
northwest waters Friday night and over the north-central waters
on Saturday. A very tight gradient between the front and the high
pressure will develop strong southerly winds over much of zone
AMZ111 on Friday, with seas of 8-9 ft. This strong southerly flow
will shift to the northwest corner of zone AMZ113 on Friday
afternoon and the remainder of the far northern waters through
early on Sunday at which point strong west to northwest winds
will make theier way into much of the northeast portion of zone
AMZ115 as the front exits the forecast waters. High pressure in
the wake of the front will slide eastward to the northeast part
of the forecast waters by late on Monday as rapidly deepening low
pressure that global model consensus depicts will track
northeastward across northern Alabama and Tennessee. A
strengthening pressure gradient covering a large area of the
southeastern U.S. and corresponding offshore waters will lead to
a significant increase of southerly flow over the northwest
waters on Monday along with building seas.

$$

.WARNINGS...Any changes impacting coastal NWS offices will be
coordinated through AWIPS II Collaboration Chat, or by
telephone:

.GULF OF MEXICO...
None.

.CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN
55W AND 64W...
None.

.SW N ATLANTIC INCLUDING THE BAHAMAS...
None.

$$

*For detailed zone descriptions, please visit:
http://www.nhc.noaa.gov/abouttafbprod.shtml#OWF

Note: gridded marine forecasts are available in the National
Digital Forecast Database (NDFD) at:
http://www.nhc.noaa.gov/marine/grids.php

For additional information, please visit:
http://www.nhc.noaa.gov/marine

$$

.Forecaster Aguirre. National Hurricane Center.

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