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AGXX40 KNHC 201857
MIMATS

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


...GULF OF MEXICO...

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.


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


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

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 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 Cobb. National Hurricane Center.

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