000 AXNT20 KNHC 111657 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Sat Dec 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 1200 UTC surface analysis and satellite imagery through 1655 UTC. ...SPECIAL FEATURE... Gulf of Mexico Gale Warning: A strong cold front will move over the NW Gulf today. Gale force winds are expected to develop in the wake of the front beginning this afternoon over the NW Gulf, then developing over the Bay of Campeche near Veracruz as the front moves E through Sun morning. Seas will build to 10 ft in the wake of the front within the strongest winds. Please refer to the latest High Seas Forecast product issued by the National Hurricane Center at the website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic waters through the coast of Guinea near 11N15W to 09N20W. The ITCZ continues near 09N20W and extends westward to 02N50W. Scattered moderate convection is observed from 03N to 14N and E of 25W. Another area of scattered showers is noted north of the ITCZ to 06N between 34W and 45W. GULF OF MEXICO... Refer to the section above for details on the Gale Warning in effect for the western Gulf. As of 15Z, a cold front enters the NW Gulf of Mexico from the the Texas/Louisiana border near 30N94W to 27N97W. Scattered showers and strong NE winds are observed behind the front. The remainder of the basin is dominated by the southwestern periphery of an expansive 1031 mb high pressure system centered in the NW Atlantic, which is maintaining dry, tranquil weather conditions. The pressure gradient between the cold front and surface ridging is producing moderate to fresh southerly winds, especially W of 84W. A recent scatterometer satellite pass depicted a small area of strong southerly winds in the SW Gulf south of 22N. Seas of 4-6 ft prevail in the central and western Gulf, with the highest seas occurring in the NW Gulf behind the aforementioned front. Elsewhere, seas are 2-4 ft. For the forecast, areas of marine fog will lower visibility to less than one nm this morning and once again tonight along the NE Gulf. The high pressure ridge extending from the Atlantic to the central Gulf will gradually shift eastward through this afternoon in response to a strong cold front that will move over the NW Gulf today. Moderate to fresh southerly return flow will set-up across the western Gulf tonight ahead of the front. Gale force winds are expected to develop in the wake of the front across the western Gulf beginning this afternoon and continue through Sun morning. Seas will build to 10 ft in the wake of the front within the strongest winds. The front will weaken as it reaches from central Florida to the SW Gulf Sun and dissipate on Mon. Fresh to strong east winds will spread westward through the Straits of Florida and to the eastern Gulf S of 26N Mon through Tue night along with building seas. CARIBBEAN SEA... A tight pressure gradient between strong ridging north of the Greater Antilles and lower pressures over northern South America is producing generally fresh to strong trades in the eastern and central Caribbean Sea, including southern Hispaniola and the Windward Passage. The strongest winds are observed in scatterometer data offshore NW Colombia. Seas of 7-10 ft prevail in the central Caribbean Sea, with the highest seas occurring offshore NW Colombia. The rest of the basin enjoys tranquil weather conditions, moderate to fresh trades, and 3-7 ft seas. For the forecast, the aforementioned pressure gradient between the ridge across the northern Caribbean and the Colombian/Panamanian low will continue to support fresh to strong easterly trades over the south-central Caribbean through the weekend and early next week. Moderate to fresh trades will prevail elsewhere. High pressure will continue to strengthen over the western Atlantic through the forecast period, resulting in pulsing fresh to locally strong northeast winds in the Windward Passage, the lee of Cuba and south of Hispaniola through Wed night. ATLANTIC OCEAN... A cold front is analyzed near 31N52W, transitioning to a weak shearline from 28N55W to 28N68W. A surface trough extends from 11N54W to 22N52W. Satellite imagery reveals scattered showers near the trough axis. High pressure dominates the remainder of the tropical Atlantic with a strong subtropical ridge centered in the NW Atlantic and a second robust Azores high pressure in the NE Atlantic. Satellite derived winds measured fresh to strong easterlies, mainly south of 25N as a result of the pressure gradient between the subtropical ridges mentioned and lower pressures over NW Africa and the deep tropics. Strong E-NE winds at the entrance of the Windward Passage are evident in scatterometer data with the strongest winds observed off the Morocco coast north of 30N. Seas of 8-12 ft are found E of 51W, with the highest seas occurring offshore Morocco. Elsewhere in the tropical Atlantic, fairly tranquil weather conditions prevail with moderate or weaker winds and 5-8 ft seas. For the forecast west of 65W, high pressure will continue to build across the region producing moderate to fresh NE to E winds S of 22N, and mainly gentle to moderate winds N of 22N through Sat night. The next cold front will move off the northeast Florida coast Sun, and reach from near 31N65W to South florida by Sun night. This front is forecast to dissipate over the southeastern waters on Mon. High pressure behind the front will bring fresh to strong northeast to east winds mainly across the waters south of 27N by Mon night. These conditions are expected to last through Tue night. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Low ash concentrations are expected in the vicinity of the volcano with very low concentrations to the southwest. 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/. $$ Nepaul