767 AXNT20 KNHC 301759 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Sat Oct 30 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. ...SPECIAL FEATURES... Showers continue to show some signs of organization near a gale force, frontal 986 mb low pressure system located near 39N49W, or several hundred nm south-southeast of Cape Race, Newfoundland. The low is moving SE near 15 kt. The low appears to be gradually losing its frontal structure, and the system is likely to transition to a subtropical storm by early next week while it meanders over the central subtropical Atlantic. There is a medium chance of development for this system within the next 48 hours. Please read the latest Tropical Weather Outlook issued by the National Hurricane center at www.hurricanes.gov and the latest High Seas Forecast issued by the National Weather Service at ocean.weather.gov/shtml/NFDHSFAT1.php for more details. ...TROPICAL WAVES... An Atlantic tropical wave is along 32W from 18N southward and moving W at 5 kt. No significant shower activity is associated with the wave. ...MONSOON TROUGH/ITCZ... A monsoon trough exits the coast of The Gambia near 13N17W to 1008 mb low pressure near 09N24W to 1011 mb low pressure near 08N31W to 07N38W. Scattered moderate and isolated strong convection is noted from 03N to 15N between the coast of Africa and 29W. The 1008 mb low along the monsoon trough near 09N24W is being monitored for potential tropical cyclone formation. The associated shower and thunderstorm activity is showing signs of organization, and environmental conditions could support some development of this system during the next couple of days as it moves generally northwestward at 10 to 15 kt. The chance of formation within the next 48 hours is low. By the middle of next week, upper-level winds are forecast to become increasingly unfavorable for further development. GULF OF MEXICO... Isolated to scattered light showers associated with a reinforcing surface trough are confined to the far eastern Gulf of Mexico, east of 85W. Otherwise, a 1018 mb surface high pressure is centered over the SW Gulf near 22N97W. The latest ASCAT pass from the late morning hours on Saturday shows fresh W to NW winds covering the eastern half of the Gulf of Mexico, locally strong in the SE Gulf. Light to gentle winds are in the SW Gulf near the high pressure. Wave heights in the SE Gulf, including the western Florida Straits and Yucatan Channel, are likely currently in the 8 to 12 ft range. Elsewhere, seas are 4 to 7 ft. For the forecast, moderate to fresh W to NW winds and choppy to rough seas to the east of 93W will diminish this evening as a cold front in the NW Caribbean continues to move slowly eastward. Remaining NW swell will gradually subside to below 8 ft by Sun morning. Fairly tranquil marine conditions are then forecast for the rest of the weekend and continuing through the middle of the upcoming week. CARIBBEAN SEA... A cold front extends from central Cuba near 22N78W to eastern Nicaragua near 13N84W. A recent ASCAT pass shows fresh NW winds covering the NW Caribbean to the west of the front. Seas are 5 to 8 ft in this area, except 9 to 12 ft in the Yucatan Channel. Scattered moderate showers and isolated thunderstorms are along the frontal boundary. The eastern end of the eastern Pacific monsoon trough extends from 13N73W to the Costa Rica/Nicaragua border. Scattered moderate and isolated strong convection is noted south of 14N between 65W-85W. To the east, moderate trades prevail over the eastern and central Caribbean, except for fresh from 12N-17N between 68W-75W. Seas are 4-7 ft in the central Caribbean, and 2-4 ft in the eastern and SW portions of the basin. For the forecast, the cold front will move through the NW Caribbean this weekend, before stalling Sun night from eastern Cuba to the offshore waters of Nicaragua. Moderate to fresh NW winds and seas of up to 8 ft can be expected in the wake of the cold front, except up to 12 ft in the Yucatan Channel through this afternoon. Elsewhere, a weak pressure gradient ahead of the front will support mainly gentle to moderate trade winds across the basin through the middle of next week, with locally fresh winds off the coast of Venezuela today. ATLANTIC OCEAN... West of 65W: A slow moving cold front extends from 31N72W to the central Bahamas near 25N76W to central Cuba near 22N78W. Scattered moderate isolated strong showers and thunderstorms are firing within 30 nm west and within 60 nm east of the front. A recent ASCAT pass shows fresh to strong S-SW winds ahead of the front to 69W with fresh to strong SW to W winds west of the front, through the NW Bahamas and Florida Straits as well as east of Florida. Seas are 7 to 11 ft to the north and northeast of the Bahamas and 5 to 7 ft farther south, closer to Puerto Rico. The cold front will move slowly east and reach from Bermuda to eastern Cuba by Sun morning. Fresh to strong winds are expected on both sides of the front through tonight, mainly north of 25N. Seas of 8 ft or greater will continue to prevail north of 26N east of 78W, as well as in the Florida Straits, lingering through Sun before decaying. The front will weaken as it stretches from 30N65W to the Turks and Caicos Islands Mon morning with gentle to locally moderate NE flow then prevailing across the southern Bahamas and the Great Bahama Bank into mid-week. East of 65W: Another cold front extends from 31N45W to 27N52W. Scattered moderate showers and thunderstorms and fresh to strong SW winds are noted within 120 nm southeast of the front. Seas of 8 to 11 ft prevail on both sides of the front, north of 26N between 40W-60W. The cold front will reach from 31N40W to 26N45W by Sun evening before slowing down. Fresh to strong SW winds and 8 to 12 ft seas will continue east of this boundary through early Tue. Seas of 8 to 11 ft in N swell will also continue west of the front during the next several days, mainly north of 27N. The subtropical surface high pressure ridge extends from a 1021 mb high pressure near 29N21W to a 1017 mb high pressure near 23N55W to 24N66W to the Turks and Caicos Islands. Another high pressure of 1016 mb is centered near 28N63W. Light to gentle winds are near the high pressure ridges. Fresh NE trades are noted from 14N-21N between the west coast of Africa and 32W. South of 26N, seas of 4 to 7 ft prevail across the eastern and central Atlantic. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Recently, there has been an increase in volcanic ash emission, with medium to high ash concentration spreading up to 30 to 35 nm west of the volcano. High volcanic ash concentration remains in the vicinity of the volcano. Marine and aviation interests should monitor this ongoing situation by reading the Volcanic Ash Advisory issued by Meteo-France at website http://vaac.meteo.fr/volcanoes/la-palma/. $$ Hagen