628 AXNT20 KNHC 121749 TWDAT Based on 1200 UTC surface analysis and satellite imagery through 1745 UTC. ...SPECIAL FEATURES... Windward Islands Ashfall Advisory: La Soufriere volcano on the island of Saint Vincent near 13.3N 61.2W is currently undergoing frequent eruptions. Volcanic ash may be reaching the ocean surface and low level visibility may be reduced. Mariners traveling within the area 18N39W to 08N40W to 10N50W to 15N62W to 17N45W to 18N39W are urged to exercise caution, especially west of 50W where the densest ash is being observed. If mariners encounter volcanic ash or floating volcanic debris, you are urged to report the observation to the National Hurricane Center by calling 305-229-4424. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends southward from the coast of Sierra Leone near 08N12W to 03N20W, where overnight scatterometer data indicates that it transitions to the ITCZ to 03N20W and to 01N35W to the coast of Brazil near 00N47W. Scattered moderate mainly along the ITCZ from 04S-04N between 26W-34W and from 00N-03N between 36W-45W. Wave height range between 4-6 ft with latest altimeter and ship obs data from south of 18N to the Equator. GULF OF MEXICO... A weak cold front extends from South Florida south-southwest to near 25N84W, where it transitions to a weakening stationary front to 26N94W. An overnight ASCAT pass indicated gentle wind speeds on both sides of the front. A surface trough extends 60 nm southeast of the cold front from 27N75W to 24N84W with showers and thunderstorms extending across the Florida Keys into the Florida Straits. A weak surface trough is located in the SW Gulf of Mexico with its axis analyzed from 24N87W to inland Mexico at 17N91W. Wave heights are in the range of 3-5 ft across the Gulf of Mexico, except for lower wave heights of 1-3 ft in the southern Bay of Campeche. The weak front will reach from the southeastern Gulf to the central Gulf this afternoon and evening and to just SE of the Gulf tonight. An upper-level shortwave trough, in combination with a surface trough along South Florida, will continue to bring scattered showers and thunderstorms over the Straits of Florida today. Some of this activity may contain frequent lightning and strong gusty winds. Another cold front will enter the northern Gulf Wed, reach from north-central Florida to southern Texas Thu and become stationary through Fri night. CARIBBEAN SEA... See the Special Features section above for details on an Ashfall Advisory issued for ongoing volcanic eruptions on St. Vincent. The latest surface analysis depicts a rather weak pressure gradient across the basin. Recent ASCAT data highlighted moderate to fresh trade winds over the central Caribbean and fresh to strong southeast winds in the Gulf of Honduras. It revealed moderate trade winds elsewhere across the basin. Mainly fair weather conditions are in place across the basin, except for isolated shower and thunderstorm activity that is occurring over the far southwestern Caribbean along the coast of Panama. Wave heights are in the 4-6 ft range across most of the basin, except up to 7 ft in some locations in the south-central Caribbean near the Colombian low pressure near 10N75W. For the forecast, moderate to fresh southeast winds will continue over the far northwestern Caribbean through the period, pulsing to strong speeds in the Gulf of Honduras. Pulses of strong NE to E winds are forecast mainly along Colombia coastal waters during the afternoons and at night through Thu. Northerly winds behind a cold front that will move over the Bahamas will funnel across the Windward Passage Tue night through Wed night supporting fresh to locally strong NE winds. Fresh NE winds are also expected over southern Cuba adjacent waters. Elsewhere, generally moderate to fresh east winds will change little through Fri night. ATLANTIC OCEAN... See the Special Features section above for details on an Ashfall Advisory issued for ongoing volcanic eruptions on St. Vincent. The latest satellite imagery shows scattered moderate convection ahead of the surface trough from 27N75W to 24N84W. A cold front 60 nm behind the trough extends from 30N75W to 26N79W and across Florida into the Gulf of Mexico. The scattered moderate convection extends from the Bahamas across the Florida Straits into the Gulf. ASCAT data pass detects an area of fresh to locally strong south to southwest winds from 22N to 31N and to the east of 74W. A 1021 mb high pressure center is analyzed near 26N21W southeast of the Canary Islands and extends westward across the central Atlantic to A ridge extends to 22N64W. Light to moderate anticyclonic winds prevail in this region. Wave heights are 6-8 ft north of the Bahamas between 70W-77W. For the forecast west of 65W, fresh to strong southwest winds NE of the Bahamas will shift eastward today ahead of a cold front. The front will reach from near 31N73W to the northern Bahamas and to South Florida early this afternoon, from near 31N67W to the southeastern Bahamas and to eastern Cuba by late tonight and the southeastern waters on Tue. The front will move east of the forecast waters on Wed as weak high pressure builds in behind it and as another cold front approaches the far northwest waters. This front will move across the water N and NE of the Bahamas from late Wed night through Fri night. Fresh to strong southwest winds are expected ahead of this front. Scattered showers and thunderstorms will continue to move offshore the South Florida coast into the Great Bahama Bank today. A surface trough is analyzed west of the high from 26N30W to 19N46W and a second trough from 25N45W to 21N54W. Scattered showers are seen with the first trough from 22N to 31N between 21W-34W. Seas range between 8 to 12 ft from 17N to beyond 31N between 28W-40W. Northerly swell over the central Atlantic will diminish today as the low moves toward the northeast and weakens. $$ MTorres