107 AXNT20 KNHC 121710 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Tue Oct 12 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 1200 UTC surface analysis and satellite imagery through 1700 UTC. ...TROPICAL WAVES... An Atlantic tropical wave has its axis along 24W, south of 17N and it is moving W at 10-15 kt. Scattered moderate to isolated strong convection is observed from 05N to 10N and between 20W and 25W. Another Atlantic tropical wave has its axis along 44W/45W, south of 16N and it is moving W at 10-15 kt. An 1130 UTC scatterometer satellite pass showed evidence of this tropical wave at the surface, along 45W/46W. The northern portion of the wave is surrounded by dry Saharan air and subsident northerly flow aloft, suppressing the development of showers and thunderstorms. Scattered moderate convection is noted along the ITCZ near the wave from 06N to 08N between 40W and 47W. A third Atlantic tropical wave is moving westward through the Leeward and Windward Islands at 10-15 kt. An upper trough along 58W is providing strong westerly shear which is disrupting the wave, and displacing the convection to the east of the center, especially from 08N to 09N and between 52W and 57W. A recent scatterometer satellite pass indicated a sharp surface trough in this convection along 56W. A Caribbean tropical wave extends from western Colombia to eastern Cuba, moving W at 15 kt. An upper low is centered over central Cuba near 22N78W. Associated divergence aloft is helping to enhance the scattered moderate to isolated strong convection north of 16N between 72W and 75W. A few showers are evident along the wave axis at 15N, and within 90 nm off the coast of northeast Colombia. ...MONSOON TROUGH/ITCZ... A monsoon trough extends from the coast of Guinea-Bissau near 12N16W to 06N30W. A segment of the ITCZ continues from 06N30W to 07N40W, with another segment reaching from 07N50W to 08N60W. Scattered moderate convection is noted from 08N to 10N between 50W and 55W. ...GULF OF MEXICO... A weak surface ridge extends from the southern Appalachians to northeast Mexico. A weak trough extends over the northeastern Gulf from 29N84W to 27N85W. Another trough is evident off the northwest coast of the Yucatan Peninsula. Dry conditions persist across the Gulf, with no significant convection noted. Moderate SE winds are noted over the western Gulf, between the ridge and lower pressure over Mexico. Seas are 3 to 5 ft in this area. Gentle easterly breezes and slight seas are noted elsewhere. For the forecast, the weak surface ridge will continue to influence the Gulf waters during the next several days. Moderate to fresh southerly winds will persist over the western Gulf between the ridge and lower pressure over the Southern Plains and northern Mexico tonight through Thu. Gentle to moderate breezes will persist elsewhere through Fri. A cold front enter the NW Gulf Fri night. ...CARIBBEAN SEA... Outside of the active tropical wave described in the Tropical Waves section, the rest of the Caribbean Sea has fairly tranquil weather conditions. Moderate to fresh trades are noted over the eastern Caribbean, with 4 to 6 ft seas. Gentle to moderate breezes and slight seas are evident across the rest of the basin. For the forecast, a tropical wave along 63W will move westward through tonight, and spread fresh to strong winds and very active weather across the NE Caribbean and adjacent Atlc, including the Virgin Islands and Puerto Rico. Northerly swell has begun to reach the regional Caribbean waters this morning and will build through Wed, including the Caribbean passages. Low pres is expected to develop E of the southern Bahamas on Thu and drift eastward into the weekend. This will weaken the pressure gradient across the Caribbean basin leading to tranquil marine conditions. ...ATLANTIC OCEAN... A broad mid to upper level low over the north coast of central Cuba near 22N77W. Associated divergent flow aloft is supporting a large cluster of showers and thunderstorms east of the Turks and Caicos Islands, from 21N to 24N between 68W and 71W. Moderate to fresh SE winds are evident near an associated surface trough reaches from near 27N71W to the southern Bahamas. Gentle to moderate SE breezes are noted elsewhere west of 65W. A second upper low is centered near 21N57W, with a mid to upper trough extending southward toward 15N58W. This pattern is supporting a disorganized area of showers and thunderstorms east of the Leeward Islands from 14N to 17N between 55W and 60W, north of an associated surface reaching along 56W from 10N to 15N. Moderate to fresh SE winds are observed east of the Leeward Islands, ahead of this trough and following a tropical wave moving into the eastern Caribbean. Weak 1019 mb ridging extends across the subtropical Atlantic from 25N to 30N, south of a string of low pressure centers across the northwest Atlantic west of 50W, and a weak stationary front reaching from the Azores Islands to near 27N30W. This pattern is supporting mostly moderate to occasionally fresh trade winds across the tropical Atlantic south of 22N, with light to gentle breezes farther north. Widespread northerly swell continues impact the region, reaching 8 to 10 ft mainly north of 15N between 30W and 70W, with 5 to 8 ft noted elsewhere. 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 closer to the surface, and eastward higher up. 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 west of 65W, 1019 high high pres centered near 27N61W will drift east and weaken through the end of the week. Very active weather is expected through Wed along and within 250 nm east of the trough extending from 27N71W to the southeast Bahamas, as it drifts eastward. Northerly swell has arrived across the regional waters overnight and this morning and will peak this afternoon through tonight east of 70W. $$ Christensen