164 AXNT20 KNHC 181717 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1815 UTC Wed Dec 18 2024 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. ..MONSOON TROUGH/ITCZ... A monsoon trough enters the Atlantic near the Sierra Leone/Liberia border and extends to 05N18W. The ITCZ continues from 05N18W to 03N35W to 03N51W. Scattered moderate convection is occurring N of the ITCZ to about 06N between 44W and 51W. ...GULF OF MEXICO... A surface trough extends from 27N89W southward through the NE Yucatan Peninsula into the northwestern Caribbean, and scattered showers and thunderstorms are occurring near the trough axis. Moderate E winds are noted to the east of this trough. Elsewhere, gentle to moderate E to SE winds prevail. Seas are generally in the 2 to 4 ft range, except 4 to 5 ft E of the trough axis to about 85W. For the forecast, moderate E winds will continue through noon to the east of a trough that extends from the Yucatan Peninsula to near 27N89W. Winds there will diminish this afternoon, while gentle to moderate winds prevail elsewhere across the basin through this afternoon. A cold front will move into the northwestern Gulf of Mexico this evening, with fresh to locally strong N winds occurring along and behind the front. The front will dissipate Thu morning over the central basin. High pressure will build over the central United States on Fri, leading to moderate N to NE winds across the Gulf. Looking ahead, gentle to moderate E winds and slight to moderate seas are anticipated for this weekend. ...CARIBBEAN SEA... A surface trough extends from central Gulf of Mexico into the northwestern Caribbean. Scattered moderate convection is noted surrounding the southern portion of the trough, particularly N of 17N and W of 83W. Elsewhere, shallow moisture, embedded in the trade wind flow is moving across the region producing isolated to scattered passing showers. The tight pressure gradient between high pressure in the central Atlantic and the Colombian low is leading to fresh to strong trades over the south-central Caribbean where seas are in the 6 to 8 ft range, with the highest seas near the coast of Colombia. Fresh to strong E winds are also noted over the NE Caribbean, including the Atlantic passages. Seas there are 6 to 8 ft in NE swell. Gentle to moderate winds dominate the remainder of the basin, with seas of 3 to 5 ft. For the forecast, a tight pressure gradient between 1034 mb high pressure NE of Bermuda and low pressure over Colombia will support moderate to fresh trade winds over the central, eastern and southwestern Caribbean through Fri morning. Winds will pulse to strong speeds each night off the coast of Colombia and Venezuela. Strong NE winds are also expected just south of Hispaniola and through the Atlantic Passages into early Thu. Atlantic NE swell will produce rough seas through the Atlantic Passages through Fri before diminishing. Elsewhere, gentle to locally moderate NE winds are expected in the northwestern Caribbean through Fri. Looking ahead, building high pressure over the Gulf of Mexico will lead to generally moderate to locally fresh NE to E winds across the basin this weekend. ...ATLANTIC OCEAN... An area of showers and thunderstorms is affecting the waters E of north-central Florida, mainly N of 28N and W of 75W. Strong SW to W winds aloft are helping to induce this convective activity. A swirl of low clouds is spinning near 29N68.5W and scatterometer data indicate a wek trough there. A cold front extends from 31N25W to 28N38W then a warm front is analyzed from 28N38W to a weak low of 1020 mb located near 27.5N45W based on visible satellite imagery. A cold front extends from the low center to about 23N60W. Fresh to strong NE to E winds follow the front, with seas of 8 to 11 ft. A strong pressure gradient between 1034 mb high pressure situated NE of Bermuda and broad low pressure across the SW Caribbean also supports a large area of fresh to strong E winds S of 27N and E of the Bahamas to about 55W, including the Atlantic exposures. Seas are 8 to 11 ft within these winds. A ridge dominates the remainder of the Atlantic forecast waters. Moderate to locally fresh trade winds and seas of 7 to 9 ft are observed across the tropical Atlantic based on scatterometer and altimeter data. Satellite derived wind data also show the presence of fresh to locally strong easterly winds between the Canary and the Cabo Verde Islands where seas of 4 to 7 ft. For the forecast W of 55W, a strong pressure gradient between 1034 mb high pressure NE of Bermuda and broad low pressure across the SW Caribbean will continue to support fresh E winds across the waters between 25N and the Greater Antilles today, with strong winds expected through the southeastern Bahamas. Farther east, a cold front analyzed from 28N41W to 23N62W will progress slowly southward through Thu, producing widespread fresh E winds both ahead and behind the front, and strong winds occurring along the front. Rough seas associated with these features will occur north of 15N through the end of the work week before seas begin to slowly subside from north to south late Thu through early Sat. Seas in excess of 12 ft will be possible along and behind the aforementioned cold front. Elsewhere, fresh trade winds and rough seas will prevail south of 15N through Thu before winds diminish to moderate speeds on Fri. A cold front will move off the coast of the southeastern United States late tonight into Thu and extend from near 31N74W to SE Florida Fri morning, and from 31N67W to eastern Cuba by Sat morning. Fresh to locally strong N to NW winds will occur behind the front. $$ GR