000 AGXX40 KNHC 211915 MIMATS Marine Weather Discussion NWS National Hurricane Center Miami FL 315 PM EDT Sun May 21 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... High pressure ridging extends from the SW Atlantic into the Mississippi Valley. The pressure gradient between the ridge and lower pressure to the west of the Gulf over Mexico is generally maintaining gentle to moderate southeast winds over the Gulf. Fresh east to southeast winds are occurring within about 30 nm of the northern portion of the Yucatan Peninsula. Scattered thunderstorms with occasional lightning strikes over the northern portion of the northeast Gulf are producing gusty winds to near 25 kt north of 27N between 84W and 88W. This activity earlier produced winds to just under 30 kt. Latest NWS doppler radars and satellite imagery reveal that this activity is undergoing weakening, however a large gust front emanating away from it to the south is followed by gusty winds possibly to the 20-25 kt range. It is expected that these winds will decease by this evening. Latest buoy observations and recent altimeter data show seas in the range of 3-5 ft over the Gulf, except for lower seas of 2-3 ft over the eastern Bay of Campeche, and temporary higher seas to 7 ft within the area of scattered thunderstorms over the northern portion of the northeast Gulf. As the ridge shifts southeastward tonight through Wednesday in response to a weak frontal boundary that is stalling along the Northern Gulf Coast, winds over the Gulf will generally remain gentle to moderate. A stronger cold front is progged by the Global models to enter the NW Gulf late Tuesday night. SW winds ahead of the front will still be light to moderate due to the weak ridging ahead of the front. The front will be supported by an upper-level trough shifting eastward toward the United States East Coast through Wednesday. This will provide strong momentum for the front to reach from the NE Gulf to the NW Yucatan Peninsula Wednesday night, and from South Florida to the Bay of Campeche by Thursday evening as it weakens. High pressure building in behind the front will be rather weak. This will provide for light to moderate northerly winds in the wake of the front Wednesday through Thursday, with the exception of moderate to fresh winds over the NE Gulf. Seas before and after frontal passage should remain in the 3-6 ft range. Seas ahead of the front may reach around 7 ft just north of zone GMZ015 on Wednesday. The thermal trough will once again form over the Yucatan Peninsula this afternoon and evening. The associated gradient will develop fresh to strong northeast to east winds north of the Yucatan Peninsula to near 22N tonight and west to 91W. These winds will diminish Monday morning as the trough moves across the SW Gulf and weakens. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... The eastern portion of the eastern Pacific monsoon trough extends to the NW coast of Colombia. Scattered to numerous showers and thunderstorms associated with the trough are noted over the SW Caribbean south of 12N. This activity is likely to continue through the next several days as model guidance is suggesting the possibility of low pressure developing along the monsoon trough towards the end of next week. The pressure gradient between Atlantic ridging and the trough is generating fresh to strong trade winds over the central Caribbean, resulting in seas of 8-11 ft between Colombia and Jamaica. The highest of these seas was indicated by a recent altimeter pass to near just north of the coast of Colombia. These winds are forecast to diminish tonight and Monday as the ridge weakens in response to low pressure moving eastward from the Eastern United States. Maximum seas of 11 ft will subside to around 8 ft by this evening, and remain about the same through Tuesday night. The gradient is expected to tighten again beginning on Wednesday as central Atlantic high pressure builds westward. The combination of this taking place and a tropical wave, presently well east of the Tropical N Atlantic, moving through the central and western portions of Caribbean will bring a surge of increasing trades trades across much of the Caribbean along with building seas possibly reaching a maximum of 10 or 11 ft over the central Caribbean Thursday through Friday, and subsiding some Friday night. Pulse type northeast to east swell will produce combined seas of nearly 8 ft over the southern sections of the Tropical N Atlantic zones beginning on Monday afternoon, and continue into Tuesday while shrinking in coverage. ...SW N ATLANTIC INCLUDING THE BAHAMAS... The main feature controlling the wind regime over the basin is is a 1023 mb high centered near 31N73W with a ridge extending westward to the southeast U.S. A surface trough is evident in Ascat data from 1332Z this morning, and in visible satellite imagery along a position from just north of the Leeward Islands and to well northeast of the forecast waters near 28N56W. Scattered showers and thunderstorms associated with this trough have moved well to the east of the forecast zones. The high near Bermuda is maintaining gentle to moderate east to southeast winds north of 22N and moderate to fresh easterly winds south of 22N. The strongest winds will continue near the approaches to the Windward Passage today, then diminish on Monday and Tuesday as the ridge weakens and shifts east-southeastward. Winds will increase and veer from the south over the NW waters beginning on Wednesday in advance of a cold front moving across the SE U.S. The front is forecast to slowly reach the southeast United States coastline late Wednesday night, then move over the northwest waters of the basin Thursday and Thursday night, and across the north-central waters north and northeast of the Bahamas late Thursday night through Friday evening while weakening. The front will primarily affect zones AMZ111 and AMZ115. Latest model guidance continues to suggest that fresh to strong southwest winds will precede the front accompanied by seas of of around 7-10 ft, with the highest of these seas north of about 29N. Winds and seas associated with the front then decrease Thursday night through Friday night as weak high pressure in the wake of the front builds takes hold of the weather regime across the basin. $$ .WARNINGS...Any changes impacting coastal NWS offices will be coordinated through AWIPS II Collaboration Chat, or by telephone: .GULF OF MEXICO... None. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... None. .SW N ATLANTIC INCLUDING THE BAHAMAS... None. $$ *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.