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AGXX40 KNHC 201857

Marine Weather Discussion
NWS National Hurricane Center Miami FL
257 PM EDT Fri Oct 20 2017

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


A weak surface trough over the SW portion of the basin extends
from 25N94W to 18N94W roughly parallel to the coast of Mexico.
High pressure over eastern KY with ridging into the NE Gulf
resulted in moderate to fresh E to SE winds mainly N of 25N.
This was confirmed by a 1522 ASCAT scatterometer pass and
platform data. Seas in the area N of 25N were generally 4 to 6
FT with lower seas, 2 to 4 FT S of 25N. High pressure across SE
US will move slowly eastward into the Atlc through the weekend.
Expect fresh E winds to continue over northern sections through
Sat Night. Winds veer and subside briefly Sun before increasing
again Mon ahead of a cold front slated to move off the Texas
coast on Sun and rapidly across the northern Gulf, extending
from near Mobile, AL to the western Bay of Campeche by early
Mon and from SW FL to the northern Yucatan by early Tue and
clears the Gulf by Tue evening. The GFS/ECMWF/NAM models appeared
to have the best handle on the timing of the front. The GFS
appears to be the sole outlier in forecasting a brief period of
gales over the far SW Bay of Campeche late Mon. The blended
grids keep winds around 30 KT late Mon which will be the basis
for the forecast at this time. High pressure builds in later Tue
with a reinforcing front/surge entering the northern Gulf
allowing winds to pick up late Tue into Wed.

55W AND 64W...

Two tropical waves will continue across the central and western
sections of the Caribbean Sea tonight, and across the western
sections and parts of Central America on Sat. E to ESE trades
of 20-25 KT with 7-11 FT seas prevail across the basin E of 75W
as confirmed by a 1428 UTC ASCAT pass, surface observations and
altimeter data. An additional area of fresh to locally strong
winds are occurring from 15N to 18N between 75W and 81W. These
conditions will shift W and expand slowly across the central
Carib through the weekend into early Mon, with seas building to
12-13 FT. Wind speeds will diminish over the Tropical N Atlc
waters by Sun. Winds diminish across the entire basin late Mon
and Tue as broad low pressure takes shape over the far SW
Caribbean late Tue and Wed just as a cold front enters the far
W Caribbean Tue Night and Wed.


A cold front extended through 31N65W to 27N72W with a surface
trough to the SW from 27N71W to 22N77W. Scattered showers and
thunderstorms were noted within 120 NM E of the front in an
area of SW winds of 20 to 25 KT N of 28N and E of 64W as noted
in a 1424 UTC ASCAT pass. The same pass indicated NE winds of 20
KT generally N of 26N W of 70W. Altimeter passes and observational
data indicated that seas have subsided below 8 FT. Rapidly
developing low pressure well N of the area will move the front
further E through Sat. Pressure gradient to the south of high
pressure over the N Atlantic will maintain fresh trades W of
70W with winds of 20-25 KT pulsing N of Cuba and Hispaniola
tonight through Sun night. Winds over the NW waters veer to the
SE and increase to 20 to locally 30 KT late Mon and early Tue
ahead of a cold front slated to move off the SE Coast just before
Sunrise Tue. GFS/ECMWF/NAM solutions offer the best timing on
the front which stalls temporarily late Tue before advancing
again early Wed. The front extends from 31N73W to east-central
Cuba by late Wed with moderate to fresh NW winds in its wake.


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


55W AND 64W...



*For detailed zone descriptions, please visit:

Note: gridded marine forecasts are available in the National
Digital Forecast Database (NDFD) at:

For additional information, please visit:


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