644 AXNT20 KNHC 151722 TWDAT Tropical Weather Discussion for North America, Central America Gulf of Mexico, Caribbean Sea, northern sections of South America, and Atlantic Ocean to the African coast from the Equator to 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1700 UTC. ...SPECIAL FEATURES... Eastern Caribbean Ashfall Advisory: An Ashfall Advisory has been reissued for La Soufriere Volcano on the island of St. Vincent near 13.3N 61.2W. Winds are blowing this new plume of volcanic ash toward the NNW from St. Vincent over the eastern Caribbean Sea, from 13.3N-15.5N between 61.2W-62.0. The ash cloud could potentially affect the island of Dominica this afternoon. The volcano remains in a state of unrest. Additional eruptions and ash plumes are possible. Mariners within the ashfall advisory area over the extreme eastern Caribbean are advised to exercise caution. Mariners who encounter volcanic ash or floating volcanic debris are urged to report the observation to the National Hurricane Center, by calling 305-229-4424. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic ocean through the coast of west Africa near 12N17W and continues SW to 08N18W. The ITCZ continues from 08N18W to 02N30W to the coast of South America near 02N51W. Scattered moderate and isolated strong convection is seen from 04N-05N between 07W-15W, from 02N-06N between 20W-28W, from 04S-01N between 32W-39W and from 00N-05N between 43W-52W, including over NE Brazil and French Guiana. Isolated moderate convection is elsewhere within 90 nm either side of the ITCZ. GULF OF MEXICO... Strong to severe thunderstorms have been occurring all morning long in the northern Gulf waters from the Florida Panhandle to the mid-Louisiana coast in association with a cold front that is moving southward in the northern Gulf of Mexico. A few of the thunderstorms contained winds gusts over 50 kt earlier, but have since begun to weaken. The storms should continue to weaken as the afternoon progresses. As of 1500 UTC, the cold front extends from Destin Florida to a 1012 mb low near 30N87W to Grand Isle Louisiana to near Rockport Texas. A recent ASCAT pass shows strong NE winds north of the front, and mainly gentle to moderate winds south of the front. Fresh SE winds are seen west of the Yucatan Peninsula. Seas are 3-5 ft across the basin, but locally higher seas are possible in thunderstorms. The cold front will stall and weaken along 27N tonight. A stronger cold front will move into the NW Gulf on Sat, with strong northerly winds and building seas expected across the western Gulf this weekend. Gale force winds are possible near the central coast of Mexico Sat night. The front will stall from central Florida to the Bay of Campeche Sun night and Mon. CARIBBEAN SEA... An Ashfall Advisory is in effect for La Soufriere volcano on the island of St. Vincent. See the special features section above for details. Weak ridging dominates Cuba and the NW Caribbean, with mainly fair weather and moderate E trades. Scattered moderate and isolated strong convection seen over Costa Rica and Panama extends into the far SW Caribbean, south of 11N and west of 80W. Farther east, the tail end of an Atlantic stationary front reaches the Lesser Antilles over Guadeloupe, where a thin line of clouds contains isolated showers and tstorms. Due to the orientation of high pressure over the west Atlantic, strong NE winds are noted south of the Dominican Republic on the latest ASCAT pass. Fresh trades cover the remainder of the central Caribbean, with moderate trades east of 67W. Seas are 4-6 ft over the central Caribbean and 2-4 ft over the eastern and NW Caribbean. The stationary front northeast of the Windward Islands will shift eastward and weaken today. Moderate to fresh trade winds, locally strong, will prevail across the Caribbean through Sun. Fresh to strong SE winds are expected in the NW Caribbean this weekend. Fresh to strong trade winds will prevail across the central Caribbean Sun night through Mon night. ATLANTIC OCEAN... West of 65W: A 1017 mb high pressure is centered near 29N70W. The latest ASCAT pass shows fresh to strong SW winds to the east of northern Florida, mainly north of 29N between 76W-81W. Scattered showers are seen mainly north of 30N between 72W and the coast of Georgia. Gentle winds prevail elsewhere closer to the high pressure. Seas are generally in the 4-7 ft range. For the forecast, a cold front will move east of northern Florida into the west Atlantic by early Fri, then stall north of the Bahamas this weekend into early next week. East of 65W: A cold front extends from 32N59W to Bermuda. Strong W winds and scattered showers are north of the front. Farther east, a pair of cold fronts extend over the central Atlantic. The trailing front is from 32N48W to 25N53W to 21N60W, dissipating to 19N69W. The leading cold front is from 32N43W to 25N48W to 21N52W. It continues SW as a stationary front to near the island of Guadeloupe. Scattered moderate showers and isolated tstorms are along and within 120 nm ahead of the leading front. Similar convection is along the trailing front north of 29N east of 49W. Fresh S-SW winds precede the leading front north of 24N and west of 37W, shown by a recent ASCAT pass. Moderate W winds are near and behind the trailing front. Seas are mainly in the 6-9 ft range over the central Atlantic, north of 23N. Both cold fronts will move eastward today while weakening. The trailing front will dissipate during the next 12- 18 hours, and the leading front will become stationary on Fri and dissipate through Sat morning. East of the fronts, surface ridging and fair weather prevail, anchored by a 1025 mb high pressure near 33N28W. Fresh NE trades are occurring from 10N-20N between 17W-38W and will continue in this area through Fri. $$ Hagen