000 AXNT20 KNHC 211012 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Sun Nov 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 0600 UTC surface analysis and satellite imagery through 1000 UTC. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coast of Guinea near 11N15W to 06N20W. The ITCZ continues from 06N20W to 04N30W to 03N50W. Clusters of moderate to isolated strong convection are noted from 00N-06N between 13W-17W. Scattered moderate convection is occurring from 01N-10N between 20W-35W. GULF OF MEXICO... High pressure of 1030 mb located over the SE of United States extends a ridge across the Gulf waters. Recent satellite-derived winds data provided observations of fresh to strong NE winds over the eastern Gulf, including the Straits of Florida. An earlier altimeter pass indicates seas of 6-9 ft within this area of winds. Moderate to locally fresh NE to E winds dominate the remainder of the Gulf waters, with the exception of E to SE winds across the NW part of the basin. The remainder of the Gulf region is covered by seas of 4 to 6 ft, except for 2 to 4 ft in the NW Gulf. A surface trough is analyzed over the SW Gulf. A few showers are E of the trough axis. Cloudiness with embedded showers is affecting the Yucatan peninsula and the SE Gulf into the Straits of Florida. These clouds are the result of the presence of strong upper-level SW winds. For the forecast, a ridge will dominate the Gulf waters today. The next cold front will enter the basin by early Mon and move quickly SE, exiting the Gulf region by Mon evening. Fresh to strong northerly wind will be expected behind the front, but mainly over the eastern Gulf late Mon into Tue. High pressure is forecast to build in behind the front. Fresh southerly return flow will set up across the NW Gulf by the middle of the week ahead of the next cold front forecast to reach the Gulf of Mexico by Thu night. CARIBBEAN SEA... Recent scatterometer data show mainly gentle to moderate trade winds across the basin, with the exception of fresh winds near the coast of Colombia and in the Gulf of Venezuela. Seas of 5-7 ft prevail in the south-central Caribbean, with 3-5 ft elsewhere, except in the lee of Cuba and in the Gulf of Honduras where seas of 1-3 ft are found. Seas of 5-6 ft are likely occurring in the Yucatan Channel. Scattered showers are thunderstorms continue to develop over the Caribbean plains of Nicaragua. A diffluent pattern aloft is helping to sustain this convective activity. A large patch of moisture, with embedded showers, covers the Leeward Islands, the US/UK Virgin Islands and Puerto Rico, and it is moving westward. A well defined swirl of clouds, with some convective activity, is noted on satellite imagery over the eastern Caribbean S of Puerto Rico. This could be related to a surface trough that crossed the Leeward Islands a couple of days ago. Elsewhere, shallow moisture embedded in the trade wind flow will continue to move across the region producing isolated to scattered passing showers. For the forecast, mainly gentle to moderate trades will prevail across much of the Caribbean Sea through Mon. A cold front will reach the Yucatan Channel by Mon evening, and extend from eastern Cuba to the Gulf of Honduras by late Tue. Fresh to locally strong winds and building seas are expected across the western Caribbean, the Windward Passage and Mona Passage likely through Thu as high pressure builds N of the area in the wake of the front. ATLANTIC OCEAN... A weakening stationary front stretches from 31N60W to near West Palm Beach, Florida. Some shower activity is along the frontal boundary. The most recent scatterometer data show fresh to strong NE winds behind the front while a pair of altimeter passes and buoy observations indicate seas of 8-11 ft in the wake of the front. Fresh to locally strong NE to E winds are also noted S of the front to about 25N and W of 70W. This is the result of the pressure gradient between the front and a 1030 mb high pressure located over the SE of United States. Farther east, another cold front enters the Atlantic forecast waters near 31N25W and extends SW to near 22N40W. A few showers are observed along the front. Within about 200 nm ahead of the front there is a trough that runs from 31N21W to 21N31W. Fresh NW winds are west of the cold front, north of 28N. Seas in NW swell, generated by a gale center located W of the Azores, are reaching the forecast waters, building seas to 10-14 ft roughly N of 29N between 30W and 40W by Sun morning. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Medium ash concentration is in the vicinity of the volcano, while low concentration is elsewhere. 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 W of 65W, the aforementioned stationary front extending 31N60W to near West Palm Beach, Florida will remain over the northern forecast waters through tonight, before lifting north ahead of a strong cold front that will move off the northeast Florida coast on Mon. The next cold front will reach from near Bermuda to eastern Cuba late on Tue. Fresh to strong winds and building seas are expected on either side of the front beginning on Tue. Winds could reach gale force N of 30N and just W of the front by Tue evening. $$ GR