AGXX40 KNHC 250839 CCA

Marine Weather Discussion...Corrected
NWS National Hurricane Center Miami FL
357 AM EDT Mon Sep 25 2017

Corrected Caribbean Sea and Tropical N Atlantic section

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 thermal trough will develop each evening over the NW Yucatan Peninsula, move W-NW across the SW Gulf during the overnight hours and dissipate over the SW Gulf waters by late each morning. Expect the trough to be accompanied by a surge of moderate to locally fresh winds that shift from NE to SE along with brief seas to 4 ft through early Tuesday. Expect a tighter pressure gradient on Tuesday evening with a fresh to locally strong wind shift along the trough axis and seas possibly to 5 ft through early Wednesday. Elsewhere, weak high pressure will continue to support mainly gentle E-SE winds and 1-3 ft seas through Wednesday night. The flow increase slightly on Thursday and through Friday over the S Central and and far western portions of the Gulf, with seas increasing a little.

The first cold front of the autumn season is depicted by model guidance to move across the northern and western Gulf waters on Thursday, and reach a position from northern Florida to the central and SW Gulf waters on Friday. Currently, it appears that this front will be rather shallow as it is expected to be followed by mainly moderate NE winds and seas of 1-3 ft, except for higher seas of 3-5 ft over the far western Gulf waters.


Ascat data from 0216Z last showed gentle to locally moderate winds across the basin W of about 70W, and a little tighter E of 70W with moderate to locally fresh E-SE winds. Seas are rather low W of 70W where 1-3 ft seas are occurring, and 4-5 ft seas E of 70W as noted in recent altimeter pass and in recent and current buoy observations. Slightly higher seas of 5-6 ft are over the tropical N Atlantic zones. The pressure gradient has begun to tighten some across the eastern and central Caribbean Sea, and will begin to tighten across the tropical N Atlantic waters this afternoon and evening as central Atlantic high pressure builds southwestward towards the tropical N Atlantic waters and NE Caribbean Sea in the wake of Hurricane Maria exiting the forecast waters of the SW N Atlantic.

The 0214Z Ascat pass indicated that E-SE trades have increased to the 20-25 kt S of about 15N to near the coast of Venezuela and between 65W-71W. Presently seas with these trades are up to 7 ft, but are forecast max out to 8 ft as the 20-25 kt trades expand westward in coverage towards much of the central Caribbean into late Wednesday morning before diminishing on Thursday. Winds are also expected to increase to 20-25 kt across the Gulf of Honduras during the evening hours beginning with this evening. Seas are forecast to build to 6-7 ft during the period of strongest winds.

Long period northerly swell is expected to reach the waters E of the Leeward Island on Tuesday, and E of the Windward Islands on Wednesday, with building seas to 7-8 ft. The swell will decay on Thursday allowing for these seas to lower below 8 ft.


Hurricane Maria is pulling off to the N with time, and as of 2 AM EDT was located about 330 nm SSE of Cape Hatteras, North Carolina moving N or 360 degrees at 7 kt with maximum sustained winds of 75 kt with gusts to 90 kt, and a minimum central pressure of 954 mb. Maria is moving N at 8 kt. This general motion with some decrease in forward speed is expected through Tuesday. On the forecast track, the core of Maria will be moving well east of the southeast coast of the United States during the day or so. The latest NHC forecast advisory has Maria exiting the forecast region around this evening. An Ascat pass from 0218Z last night nicely highlighted winds of 20-33 kt covering most of the forecast waters N of 25N and NE of the Bahamas. Both altimeter data and buoy reports reveal that seas 12 ft or greater are occurring to the N of 24N between 66W-80W. Buoy 41047 located at 27.5N71.5W is currently reporting SW winds to near 35 kt along with combined seas of 17 ft. Just a short while ago, it reported combined seas of 21 ft. Although Maria is soon on its way out of the basin, the main issue that will plague much of the forecast waters will be swell with primary direction from the NW, except in mixed directions over the waters N and NE of the Bahamas. In addition, seas of 8 ft are along the entrances to the Bahamas passages. Wave model guidance suggests that the swell will slowly decay through the end of the week while the bulk of the swell group shifts to the NE portion of the basin. The seas of 8 ft along the entrances to the Bahamas passages will subside to less than 8 ft by late on Tuesday.

Of note, swells generated by Maria are increasing along portions of the southeastern United States coast and Bermuda and will be increasing along the Mid-Atlantic coast today. Swells also continue to affect Puerto Rico, the Virgin Islands, the northern coast of Hispaniola, the Turks and Caicos Islands, and the Bahamas. These swells are likely to cause life-threatening surf and rip current conditions. Otherwise, in the wake of Maria a surface trough will extend from the N-central forecast waters SW to near the Central Bahamas through Wednesday night then become diffuse Thursday as central Atlantic high pressure builds westward across the eastern portion of the area. Scattered showers and thunderstorms are possible with the trough. On Friday, the ridge is forecast to extend E to W near 26N as a weak cold front approaches the SE United States coast, and far NW waters.


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



.AMZ113...ATLANTIC FROM 27N TO 31N BETWEEN 70W AND 77W... Hurricane Warning today. Tropical Storm Warning tonight into Tue.
.AMZ115...ATLANTIC FROM 27N TO 31N BETWEEN 65W AND 70W... Tropical Storm Warning tonight.


*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.