829 AXNT20 KNHC 181728 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Sat Mar 18 2023 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... Atlantic Significant Swell Event: A cold front extends from 31N37W to near Guadeloupe in the Leeward Islands. Large and long period NW swell is analyzed behind this front. Seas in excess of 12 ft are north of a line from 31N40W to 25N50W to 31N56W. Seas range from 12-14 ft with highest seas in the discussion waters near 31N47W. Swell period is 10-12 seconds. This swell will continue to propagate eastward and gradually diminish through tonight, with seas subsiding below 12 ft by tomorrow morning as the front moves E of 35W. Gulf of Mexico Gale Warning: A strong cold front extends from the Florida Big Bend area to near Veracruz, Mexico. This front will reach from near Fort Myers, Florida to the eastern Bay of Campeche overnight, spreading strong to near-gale force northerly winds to the northeastern and central Gulf. Gale force NW to N winds will begin early tomorrow morning in the SW Gulf. By tomorrow evening, frequent gusts to gale force are expected in the south-central Gulf. Seas currently 8-10 ft in the lee of the front will build to 12 and 14 ft in gales and the persistent strong to near gale force N winds. Winds and seas will gradually diminish Sun night through Mon as the front stalls and dissipates over the far northwest Caribbean. Please read the latest High Seas Forecast at https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and Offshore Waters Forecast at https://www.nhc.noaa.gov/marine/offshores.php for more details on the Gale Warning and Significant Swell above. East Atlantic Gale Warning: Meteo-France has issued a gale warning for the following offshore zones: AGADIR, from 18/1200 UTC to at least 19/1200 UTC, and TARFAYA, from 18/1800 UTC to 19/0600 UTC. N to NW winds to Force 8 are expected. Seas will range from 9-13 ft with highest seas in the area of strongest winds. For more information please see the Meteo-France High Seas Forecast and Warning at website: https://wwmiws.wmo.int/index.php/metareas/affiche/2 ...MONSOON TROUGH/ITCZ... A monsoon trough enters the Atlantic along the African coast near the border of Sierra Leone and Liberia, and extends west- southwestward to 03N22W. Scattered moderate convection is seen near the monsoon trough from 01N to 06N between 10W and 20W. The ITCZ continues westward from 03N22W across 02N35W to the Amazon River Delta, Brazil at the equator and 50W. Showers are noted in the vicinity of the ITCZ. GULF OF MEXICO... Please see the SPECIAL FEATURES section for information on a GALE WARNING. The strong cold front described in SPECIAL FEATURES is currently accompanied by scattered moderate convection from 24N to 26N between 85W and 89W. Showers and tstorms are evident elsewhere along the boundary. 1012 mb low pressure is centered near 23N92W, with a pre-frontal surface trough extending north-south through the low pressure. The low pressure should be absorbed by the front later this afternoon. Behind the front, N winds are strong to near gale force with 8-10 ft seas. Seas are locally 11 ft in the NW Gulf and W Bay of Campeche. Ahead of the front, S winds are moderate to fresh with 4-7 ft seas. For the forecast, wind will reach gale force off Veracruz, Mexico overnight as the front extends from southwest Florida to the northwest Yucatan Peninsula by early Sun. Frequent gusts to gale force are possible behind the front late Sun over the central Gulf. The front will move southeast of the area by early Mon. High pressure building in the wake of the front will allow winds and seas to diminish across most the Gulf through Mon, although fresh to strong winds over the western Gulf will persist and shift SE Mon night into Tue. Looking ahead, winds and seas will continue to diminish across the basin through mid week. CARIBBEAN SEA... The old cold front that has been slowly sinking southward in the NE Caribbean lost all thermal and moisture contrast overnight. Surface observations and scatterometer data this morning showed a sharp increase in E wind speeds from gentle speeds on the equatorward side to fresh speeds on the poleward side of the remnant boundary. Therefore, a shearline is now analyzed in the NE Caribbean, from Guadeloupe to 16N70W. In the Central Caribbean, trades are moderate to fresh, pulsing to strong speeds in the south-central Caribbean off the coast of Colombia. Seas in the Eastern and Central Caribbean are 4-6 ft. In the Western Caribbean, S winds are gentle to moderate with 3-5 ft seas. For the forecast, high pressure north of the area behind the shearline will continue to support fresh to occasionally strong NE to E winds and moderate to occasionally rough seas across the eastern and central Caribbean through Mon morning. Large northerly swell will persist at the Atlantic passages through tonight. Fresh to strong easterly winds will continue to pulse off Colombia through Mon, then increase to between strong and near-gale by Tue. Winds and seas are expected to increase in the Yucatan Channel by Sun night as a cold front moves into the area. These winds and seas should gradually diminish through Tue as the stalled front dissipates. ATLANTIC OCEAN... Please see the SPECIAL FEATURES section for information about a SIGNIFICANT SWELL EVENT and an EAST ATLANTIC GALE WARNING. In the lee of the cold front described in the SPECIAL FEATURES section, seas in excess of 8 ft are north of a line from 31N32W to 14N60W to 20N67W to 31N61W. West of 67W in the W Atlantic, seas are 4-7 ft. 1024 mb high pressure near 29N63W is supporting gentle to moderate anticyclonic flow across the W Atlantic, except in the far NW waters where S winds are fresh to strong ahead of a cold front over the SE United States. Elsewhere in the central and eastern Atlantic, 1026 mb high pressure centered north of the area dominates the basin. Gentle NE to E winds prevail over these waters. An area of 8-11 ft seas in N swell is from 12N to 25N east of 34W. For the forecast W of 55W,the high pressure centered south of Bermuda near 29N63W will support fresh to occasionally strong E to SE winds off Hispaniola through Sun. Large northerly swell west of 70W will subside through Sun, except for northeast of the northern Leeward Islands. Meanwhile, expect fresh to strong southerly flow and building seas north of 29N between northeast Florida and Bermuda through this evening, ahead of a cold front moving off the northeast Florida coast later this morning. The front will move east and stall from Bermuda to the Straits of Florida by early Mon. Looking ahead, winds and seas will increase north of the stalled front Mon through mid week with NE swell. $$ Mahoney