732 AXNT20 KNHC 111133 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Sun Apr 11 2021 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 0600 UTC surface analysis and satellite imagery through 1015 UTC. ...SPECIAL FEATURES... East Atlantic Gale Warning: ASCAT data from last night revealed gale-force southwest winds from 28N- 31N between 30.5W- 33W. These gales are occurring on the SE side of a large 990 mb low pressure system centered near 35N43W. The low is moving NE at 20 kt. Wave heights are in the 11-17 ft range in the area of gale force winds. The MeteoFrance forecast indicates that the winds there will diminish below gale force soon. Windward Islands Ashfall Advisory: La Soufriere volcano on the island of Saint Vincent near 13.3N 61.2W is undergoing frequent eruptions. Satellite imagery shows the volcanic ash plume spreading well to the east and northeast of St. Vincent, roughly in an area from 10N-18N between 40W-62W, which includes Barbados. Violent volcanic eruptions may occur suddenly without warning. Volcanic ash may be reaching the ocean surface east northeast of St. Vincent. Mariners should exercise caution, and report volcanic ash or floating debris to the National Weather Service by calling 305-229-4424. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends southward from the coast of Guinea-Bissau near 12N16W to 04N23W, where overnight scatterometer data indicates that it transitions to the ITCZ to 02N32W to 01N49W. Scattered moderate to isolated strong convection is well south of the ITCZ along the coast of Brazil between 36W-41W. GULF OF MEXICO... The earlier observed cluster of strong thunderstorms that was over the southeastern Gulf has dissipated. A new and increasing large thunderstorm complex has quickly developed over the NE Gulf from 26N-30N between 85W-90W. Similar activity is over northern Florida. With a rather potent upper-level trough located over the eastern Gulf and ample available moisture in place at the low- levels and daytime heating later on, expect for additional clusters of strong to severe thunderstorms to develop over the NE Gulf and over north-central Florida during this morning. This activity is likely to persist into the afternoon hours. The main hazards associated with these storms are likely to be wind gusts of 35-45 kt and frequent lightning. The storms will propagate east-southeast during the day. Elsewhere over the Gulf as of 09Z, a weak cold front extends from south-central Louisiana to 26N96W, where it becomes stationary inland Mexico just south of Brownsville. A trough out ahead of it extends from 28N92W to a 1003 mb low near 22N95W and to near 19N95W. Scattered moderate convection is within 30 nm of 28N90W. Overnight ASCAT data shows fresh east-southeast winds over the east-central Gulf, with gentle to moderate winds elsewhere. Wave heights are in the 3-6 ft range across the basin. Fresh southerly winds will prevail across the most of the basin this morning to the east of the cold front. The cold front will reach from the Florida panhandle to the central Gulf by early this evening, and weaken further to a trough as it reaches the southeastern Gulf Mon and dissipates late Mon. The aforementioned upper-level trough will also aid in the development of scattered showers and thunderstorms over the rest of the eastern Gulf waters today. Some of this activity may contain frequent lightning and strong gusty winds. 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. Overnight ASCAT data shows fresh trades over most of the basin, while fresh to strong east- southeast winds are in the Gulf of Honduras. Wave heights are in the 3-6 ft range, except for slightly higher wave heights of 5-7 ft in the central Caribbean area. The earlier noted scattered moderate thunderstorm activity over northwestern Honduras and the Gulf of Honduras has dissipated. Isolated showers and thunderstorms are over the northern part of South America. Isolated showers are possible over the far eastern Caribbean. ATLANTIC OCEAN... See the Special Features section above for details on an Ashfall Advisory issued for ongoing volcanic eruptions on St. Vincent. The earlier observed line of scattered moderate showers and thunderstorms that was east of the Florida peninsula dissipated. Isolated showers are possible from 25N to 32N between 72W-78W.between 76W-79W. Isolated showers are noted over the waters between the Bahamas Cuba and over some parts of the Straits of Florida and Keys. Buoy observations indicate that there are fresh southerly winds over the far western part of the area. This in advance of a cold front that is presently moving across the southeastern U.S. The thunderstorm complex over the NE Gulf of Mexico will cross the Florida peninsula and move offshore to the Atlantic waters during the day today and into this evening. Expect wind gusts of 35-45 kt and frequent lightning this afternoon, especially in the waters extending offshore between Daytona Beach and West Palm Beach Florida. Outside of the thunderstorms, expect for the fresh southerly winds over the NW waters to shift eastward through Mon ahead of the aforementioned cold front that will move off the southeastern U.S. coast tonight. The front will reach from near 31N75W to east-central Florida early Mon, from near 31N70W to the central Bahamas and to east-central Cuba Mon evening and the southeast waters by late Tue. The front will move east of the forecast waters on Wed as weak high pressure builds in behind it. The high pressure will be displaced southeastward through Thu night as yet another cold front moves across the northwest and north-central waters. Fresh to strong southwest winds are expected to precede this front. Scattered to numerous showers and thunderstorms, some strong to severe, are expected to push off the Florida coast today. A large occluded gale-force low pressure system north of the area centered near 35N43W is producing a large area of strong westerly winds north of 26N between 30W-58W. Seas are 11-17 ft in this area. Northerly swell from this system, with seas in excess of 8 ft, is affecting most of the central Atlantic north of 21N between 26W-63W. Fast-moving small cells of showers and thunderstorms are seen rotating cyclonically in the southern semicircle of this low. This activity is brushing the waters north of 29N between 39W-48W. Cold air instability aloft is helping to sustain this activity. A trough is analyzed over the central Atlantic along a position from near 32N30W, south-southwestward to 25N36W to 20N44W and to near 15N54W. Upper-level diffluence to the east of the northeastern portion of the surface trough is aiding an area of scattered moderate convection east of the trough from about 24N to 32N between 23W-31W. A 1018 mb high is centered near the Canary Islands, with a ridge stretching southwestard to 23N27W and to near 17N41W. A 1017 mb high is centered near 28N68W. Associated gentle anticyclonic winds are occurring between 61W-72W. $$ Aguirre