000 AXNT20 KNHC 111005 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Mon Oct 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 31N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 0600 UTC surface analysis and satellite imagery through 1000 UTC. ...TROPICAL WAVES... A tropical wave located along 54W or about 350 nm east-southeast of the Windward Islands continues to produce disorganized cloudiness and thunderstorms. Some slow development is possible during the next day or two while the system moves west-northwestward at about 10 to 15 kt toward the Lesser Antilles. After that time, strong upper-level winds are expected to limit further development. Regardless of development, the system could produce locally heavy rainfall and gusty winds across portions of the central and northern Lesser Antilles on Tuesday, and across the Virgin Islands and Leeward Islands on Wednesday. Another tropical wave located over the eastern Caribbean Sea along 67W/68W is producing a large area of disorganized cloudiness and showers. Unfavorable upper-level winds are expected to limit development over the next day or so, but environmental conditions could become a little more conducive for some gradual development of the system when it is located near the southeastern Bahamas around midweek. Regardless of development, locally heavy rainfall is possible over portions of the Lesser Antilles, Puerto Rico, and Hispaniola during the next couple of days. Satellite derived wind data clearly indicate the wind shift associated with the wave axis, with fresh to locally strong E to SE winds behind the wake, and moderate to locally fresh NE to E winds ahead of the wave axis. A third tropical wave is near 83W and extends from just S of the Isle of Youth, Cuba to Costa Rica, moving W at 15 to 20 kt. Scattered showers are near the wave axis. ...MONSOON TROUGH/ITCZ... A monsoon trough extends through the coast of Senegal near Dakar to S of the Cabo Verde Islands to 08N30W. The ITCZ stretches from 08N30W to 06N47W. Scattered moderate isolated strong convection is noted from 04N to 08N between 15W and 21W. Scattered moderate convection is from 04N to 08N between 30W and 40W. ...GULF OF MEXICO... A ridge dominates the Gulf waters. Recent scatterometer data show moderate to fresh southerly return flow over the NW Gulf ahead of a cold front approaching the coast of Texas. Mainly moderate to fresh SE to S winds prevail over the western Gulf, particularly W of 94W, while gentle to moderate E to SE winds are noted elsewhere. Seas are 4 to 6 ft over the NW Gulf, 3 to 5 ft over the remainder of the W Gulf N of 22N W of 94W, and 1-3 ft elsewhere. For the forecast, a ridge will continue to dominate the Gulf waters during the next several days. Moderate to fresh southerly winds are expected over the western Gulf between the ridge and lower pressure over the Southern Plains and northern Mexico through Thu. Gentle to moderate breezes will persist elsewhere through Fri. ...CARIBBEAN SEA... A tropical wave is moving across the eastern Caribbean, and a second tropical wave is forecast to approach the Lesser Antilles on Tue. Please, see the Tropical Wave section for more details. Both systems have a low chance of tropical cyclone formation through 48 hours, and also through 5 days. Outside of the tropical wave located over the eastern Caribbean, moderate trades are noted S of Hispaniola, with gentle to moderate winds elsewhere across the basin. Seas are 4-6 ft near the tropical wave, 3-5 ft over the remainder of the E and central Caribbean, and 1 to 3 ft over the NW caribbean. Convection continues to flare-up over eastern Cuba ahead of an upper-level trough that crosses just E the Isle of Youth, Cuba to the Gulf of Honduras. Fresh to strong winds are seen per scatterometer data just S of eastern Cuba due to the convective activity. For the forecast, the tropical wave currently located along 54W could produce locally heavy rainfall and gusty winds across portions of the central and northern Lesser Antilles on Tuesday, and across the Virgin Islands and Leeward Islands on Wednesday. A second tropical wave now moving across the eastern Caribbean, with axis along 67W/68W will move over Hispaniola today. Locally heavy rainfall is possible over portions of the Lesser Antilles, Puerto Rico, and Hispaniola during the next couple of days in association with this second tropical wave. A northerly swell event over the Atlantic waters will reach the NE Caribbean passages by Tue. ...ATLANTIC OCEAN... A surface trough extends southwestward from a non-tropical low pressure area located just off the North Carolina across the NW Bahamas to western Cuba. This trough continues to support scattered showers and thunderstorms. An area of showers and thunderstorms is just E of the central Bahamas and covers the waters from 23N to 27N between 71W and 75W. A diffluent pattern aloft is helping to induce this convective activity. Another area of scattered showers with embedded thunderstorms is noted N of 26N between 30W and 40W. This convective activity is associated with a pre-frontal trough that extends from 31N30W to 27N50W. The remainder of the Atlantic is under the influence of a ridge, anchored on a 1032 mb high pressure located well NE of the Azores. The pressure gradient between the ridge and lower pressures over W Africa is resulting in a belt of moderate to fresh trade winds roughly from 17N to 22N and E of 40W to the coast of Mauritania. The Cumbre Vieja volcano, that is on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Currently, significant volcanic ash is seen in the vicinity of the volcano drifting southward, then eastward later today. Marine and aviation interests should monitor this on-going situation, by reading the Volcanic Ash Advisory, that is issued by Meteo-France, at http://vaac.meteo.fr/volcanoes/la- palma/. For the forecast W of 65W, the surface trough located just E of Florida and associated weather will move little today, then drift E and weaken through midweek. Farther south, a low pressure is forecast to develop around mid-week near the SE Bahamas. This will be associated with the northern extent of a tropical wave currently moving across the eastern Caribbean. A northerly swell event across the Atlantic will reach the SE waters by Tue. $$ GR