000 AXNT20 KNHC 182313 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Sun Dec 19 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 1800 UTC surface analysis and satellite imagery through 2300 UTC. ...MONSOON TROUGH/ITCZ... The ITCZ extends from the coast of Sierra Leone near 08N13W to 05N30W to 08N36W, then continues west of a surface trough from 08N40W to near the Venezuela-Guyana border. The surface trough runs from 12N37W to 05N38W. Isolated showers are near the trough axis. Scattered moderate convection is from 05N-07N between 20W-30W. ...GULF OF MEXICO... High pressure located over the western Atlantic near 29N63W extends a ridge across Florida into the Gulf of Mexico. Gentle to moderate anticyclonic flow is noted over the Gulf waters under the influence of this system. Seas are generally in the 3-5 ft range. A cold front is approaching the coast of Texas generating numerous showers and thunderstorms. Similar convective activity is seen ahead of the front over parts Alabama and Louisiana. Scattered showers and isolated thunderstorms are flaring up over the eastern Gulf and also over the west-central Gulf. Upper diffluence is helping to induce this convection. For the forecast, the cold front will move off the Texas coast this evening, bringing strong to near gale-force winds to the NW Gulf and along the coast of Mexico Sun into Mon. The front will move slowly until a low pressure forms along the frontal boundary in the central Gulf on Mon, then moves northeastward into the SE U.S. Tue, dragging the cold front across the Gulf as it does. Winds and seas will subside Tue night through Thu in the wake of the front, as weak high pressure builds in across the Gulf. Corpus Christi has issued a gale warning for frequent gusts to gale force for the coastal waters through early Sun morning. ...CARIBBEAN SEA... The tight pressure gradient between high pressure located over the western Atlantic near 29N63W and the Colombian/Panamanian low is resulting in fresh to strong winds across the central Caribbean Sea just S of Jamaica, with the strongest winds occurring offshore NW Colombia. Satellite derived wind data confirmed the presence of these winds. Fresh to locally strong winds are present across the remainder of the E and central Caribbean, with moderate to fresh E to SE winds over the NW Caribbean. Seas of 9-12 ft dominate the waters E of the Lesser Antilles and in the south-central Caribbean, with seas of 6-8 ft elsewhere S of 18N and E 82W. Seas of 8-9 ft in NE swell are affecting the Atlantic passages E of La Mona Passage. In the NW Caribbean, seas are in the 3-5 ft range. Scattered showers and isolated thunderstorms are seen over NE Honduras and northern Nicaragua as well as over parts of the Gulf of Honduras. Elsewhwere, patches of low level moisture, embedded in the trade wind flow, are observed elsewhere producing isolated to scattered passing showers. For the forecast, the high pressure over the western Atlantic will support fresh to strong trades over the central and E Caribbean and tropical N Atlantic this weekend. The high will move east for the start of next week, leading to weaker trades. Large N to NE swell will continue in the tropical N Atlantic as well as Mona and Anegada Passages through Mon. Looking ahead, a cold front should move through the Yucatan Channel late Tue and may reach Honduras and Nicaragua by Thu. ...ATLANTIC OCEAN... The above mentioned high pressure located near 29N63W dominates the central and western Atlantic, the Bahamas and the State of Florida. Farther E, a cold front enters the forecast waters near 31N18W then continues SW to near 21N30W. A well defined shearline begins at 22N30W and stretches westward along 17N45W to 18N60W. Fresh to strong NE winds are on the north side of the shearline W of 35W, with mainly moderate NE winds in the south side of the shearline. The pressure gradient between the high pressure and lower pressures in the vicinity of the ITCZ also supports fresh to locally strong NE-E winds from 10N-16N between 40W and the Lesser Antilles. Seas of 9-12 ft in NE swell are in this region. A pair of altimeter passes indicate seas of 9-13 ft in the wake of the front between 40W-55W. For the forecast W of 65W, high pressure over the western Atlantic is inducing fresh to strong trades near the Greater Antilles and mainly gentle winds elsewhere. These conditions will prevail through early Sun, before the high shifts to the east and winds relax. A cold front will move off the SE U.S. coast Sun night and continue eastward, bringing strong to near gale force winds on both sides of the front mainly north of 29N. Low pressure is likely to move northeastward off the SE U.S. coast Tue, bringing another potential for strong to near gale force winds on Wed and Thu. Seas of 8-9 ft in NE swell affecting the waters S of 25N and E of the Bahamas will subside on Sun. Large N swell impacting the Atlantic forecast waters W of 35W will gradually subside beginning on Sun. $$ GR