000 AXNT20 KNHC 211651 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 UTC Thu Oct 21 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 1650 UTC. ...TROPICAL WAVES... The axis of a tropical wave is along 40W, south of 17N and it is moving W at 10-15 kt. The wave is embedded in Saharan dry air, suppressing the development of showers and thunderstorms. However, satellite imagery depict a broad surface trough with a few light showers. A tropical wave has been added to the surface analysis based on wave guidance and satellite imagery. The axis of the tropical wave is along 54W, south of 17N. Scattered moderate to isolated strong convection is noted within 150 nm on both sides of the wave axis, south of 10N. The wave is embedded in Saharan dry air N of 10N. The axis of a tropical wave is along 65W, south of 21N and it is moving W at 10-15 kt. This wave is in the leading edge of a large area of Saharan dry air. Scattered moderate convection is observed within 100 nm on both sides of the wave axis, mainly south of 14N. The axis of a tropical wave is along 73W, south of 21N, extending from the Haiti to N Colombia, and it is moving W at 10-15 kt. A few showers are noted near the wave axis. ...MONSOON TROUGH/ITCZ... The monsoon trough extends across the coast of Senegal from 14N17W to a 1012 mb low pressure near 13N19W to 03N26W. The ITCZ continues from 03N26W to 02N44W. Aside from convection noted in the tropical waves section above, scattered moderate convection is noted from 05N to 10N and E of 22W. GULF OF MEXICO... The 1025 mb subtropical ridge near Bermuda extends into the Gulf of Mexico. A recent scatterometer satellite pass indicate fresh to locally strong NE winds occurring in the Florida Straits and SE Gulf, mainly within 100 nm of the Florida Keys and the NW Cuban coast. Moderate or weaker anticyclonic winds are present in the rest of the Gulf. A surface trough extends along 94W from 17N to 22N and it is producing isolated moderate convection over the W Bay of Campeche. A few showers are also noted in the SE Gulf and within 60 nm of the N Gulf coast. Seas of 3-6 ft are found E of 92W, with the highest seas occurring in the Florida Straits. Seas of 1-3 ft prevail elsewhere in the basin. For the forecast, the aforementioned ridge will dominate the Gulf waters through early next week. Moderate to fresh easterly winds are expected across the SE Gulf into tonight. Gentle to moderate winds will prevail elsewhere. CARIBBEAN SEA... A surface trough near the E coast of Yucatan is producing scattered showers and isolated thunderstorms within 60 nm of the trough axis, affecting portions of the Gulf of Honduras. A few showers are also found in the central and SW Caribbean, mainly south of 17N. Recent satellite-derived winds show fresh to locally strong trades in the SE Caribbean, likely associated with the leading edge of the dry Saharan airmass entering the region. Moderate or weaker trades are present in the rest of the Caribbean Sea. Seas of 4-6 ft are found in the E, central and SW Caribbean, with the highest seas occurring in the SE Caribbean. Seas of 2-4 ft are prevalent elsewhere. For the forecast, high pressure N of the area will support fresh to locally strong trades E of the Windward Islands through Sun night. During this period, moderate to fresh winds are expected over the south- central Caribbean, with winds reaching locally strong in the Venezuela basin. Gentle to moderate tradewinds will prevail elsewhere. ATLANTIC OCEAN... The main feature of interest in the tropical Atlantic is a dissipating stationary front that stretches from 31N42W to 26N54W and then continues as a trough to the SE Bahamas. Scattered moderate to isolated strong convection is occurring within 120 nm of the trough axis, especially from 52W to 72W. Scatterometer satellite data depict fresh to strong NE winds N of the trough axis to 27N and between 56W to the SE coast of Florida. Seas of 4-7 ft are present W of 60W, with the highest seas occurring in the area of strong winds. A weak surface trough is found from 18N33W to 26N35W, but there is no deep convection associated with this feature. The rest of the basin is patrolled by the robust 1025 mb high pressure system near Bermuda and the strong 1030 mb high pressure system near the Azores, resulting in fairly tranquil weather conditions. The pressure gradient resulting from these high pressures and lower pressures over South America is causing a large area of fresh and strong trades S of 20N and between 37W and the Lesser Antilles. Another area of fresh to strong NE winds is noticed in the satellite-derived wind data in the NE Atlantic, N of 24N and E of 28W. Seas in both regions are 6-9 ft. Moderate or weaker winds and seas of 4-7 ft prevail in the rest of the basin. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Ash emission is on-going. Moderate to high volcanic ash is expected in the vicinity of the volcano. Elsewhere, light volcanic ash concentration is drifting south. Marine and aviation interests should monitor this ongoing situation by reading the Volcanic Ash Advisory issued by Meteo-France at http://vaac.meteo.fr/volcanoes /la- palma/. For the forecast west of 65W, high pressure will shift eastward across the W Atlantic along 31N-32N into Fri, producing moderate to fresh winds. Surface troughing will then prevail over the area through early next week. $$ DELGADO