000 AXNT20 KNHC 211805 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Tue Dec 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 1200 UTC surface analysis and satellite imagery through 1630 UTC. ...SPECIAL FEATURES... .GULF OF MEXICO GALE WARNING... A strong frontal low pressure system of 1001 mb located near Tampa, Florida will sustain N to NE near-gale to gale winds off the Florida W coast just S of the Big Band Area through late this afternoon. Seas across the NE Gulf range from 8 to 10 ft. As it moves northeastward across the Florida Peninsula and exits into the Atlantic Ocean this evening, both winds and seas should gradually subside across the NE Gulf. Please refer to the latest High Seas Forecast, issued by the National Hurricane Centered the following website: https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml, for more details. .ATLANTIC GALE WARNING... The aforementioned low pressure is going to exit into the Atlantic off NE Florida this evening. This will cause SE to SW winds to increase offshore from the Florida-Georgia coast, reaching strong to near-gale with frequent gusts to gale force. Sustained winds should increase to between near-gale and gale later tonight. Seas will build to between 8 and 10 ft by this evening and then peak at 10 to 13 ft through Wed morning. Please refer to the latest High Seas Forecast issued by the National Hurricane Center, at the following website: https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml, for more details. ...MONSOON TROUGH/ITCZ... An ITCZ meanders west-northwestward from SW of the Liberia coast at 03N14W to 05N41W to near Trinidad and Tobago. Scattered moderate convection is found up to 150 nm from either side of the ITCZ. The E Pacific monsoon trough is triggering scattered showers and isolated thunderstorms over Panama and nearby Caribbean waters. ...GULF OF MEXICO... Please see the Special Features section above for details on gales and high seas over the NE Gulf. A cold front extends southwestward from a strong 1001 mb low pressure near Tampa, Florida to the Yucatan Peninsula near the Mexico- Belize border. Scattered showers and thunderstorms are occurring along and up to 180 nm SE of the front, including the Yucatan Channel, Florida Keys and Straits of Florida. Moderate to fresh with locally strong SW to NW winds and seas at 7 to 9 ft are present near the front. A surface trough runs westward from the same low to the N central Gulf. Scattered showers are seen across the N central and NE Gulf. Farther west, a 1021 mb high near Tampico, Mexico is dominating the W edge of the Gulf with moderate winds and seas of 5 to 7 ft. Tight pressure gradient between this high and the strong low near Tampa, Florida is generating fresh to strong northerly winds with seas of 6 to 9 ft across the NW and central Gulf. For the forecast, the aforementioned low will track NE and move inland into Florida by early this afternoon. Gales will end for the NE Gulf late this afternoon. Showers and some strong thunderstorms will continue to be possible over the far SE Gulf and Florida Straits before the front moves SE of the area this evening. Fresh to strong winds and seas of 8 to 10 ft behind the front will gradually subside late tonight and early Wed. High pressure crossing the northern Gulf will lead to tranquil conditions Wed night through Thu, but by Fri and into the weekend, fresh to possibly locally strong S return flow will develop in the western Gulf. ...CARIBBEAN SEA... A cold front extends southwestward from the Yucatan Channel to the Mexico-Belize border. Scattered showers and isolated thunderstorms are evident across the NW edge of the Caribbean Sea, including the Mexico-Belize coast. A surface trough embedded with the trades is producing scattered showers and isolated thunderstorms over the N Leeward Islands and Virgin Islands. Refer to the Monsoon Trough/ITCZ section for additional weather in the basin. Moderate to fresh ENE trades and seas at 5 to 7 ft are found over the S central basin. Moderate to locally fresh SE to SW winds with seas at 2 to 4 ft are occurring near the cold front. Gentle to moderate ENE trades and seas of 4 to 5 ft prevail for the remainder of the basin. For the forecast, the cold front will gradually stall from the Windward Passage to offshore Nicaragua for the latter part the week. Fresh N winds can be expected behind the front. Elsewhere, moderate to fresh trades will prevail over the central and E basin through tonight. A weakening pressure gradient will lead to less wind Wed and Thu. For tropical Atlantic waters E of the Lesser Antilles, fresh to strong trades and large N to NE swell will prevail into tonight. ...ATLANTIC OCEAN... Please see Special Features section above for information on gales that will develop offshore from the Florida-Georgia coast this evening through Wed morning. A frontal boundary runs northeastward from a strong 1001 mb low near Tampa, Florida to a 1007 mb low offshore from Jacksonville, Florida. This boundary then turns eastward across the Atlantic to 28N70W before turning east-northeastward to beyond 31N45W. Scattered to numerous showers and thunderstorms are seen over Florida and N of 27N between 74W and the Florida-Georgia coast. Scattered showers are found farther E near the boundary, N of 28N between 40W and 74W. The southwestern end of a cold front is triggering scattered showers over the Canary Islands. A broad surface trough along the Mauritania-Senegal coast is producing scattered showers and isolated thunderstorms along the central African coast and near the Cabo Verde Islands. N of 28N, moderate to fresh winds are present near both frontal boundaries N of 28N between the Canary Islands and 70W. While seas at 7 to 10 ft dominate the first boundary between 40W and 70W, and 10 to 14 ft near the second boundary between the Canary Islands and 40W. Moderate SE winds and seas at 6 to 9 ft are noted from the Bahamas westward to the central and S Florida coast. The large Mid-Atlantic ridge is providing light to gentle winds with seas at 5 to 7 ft from 21N to 28N between the NW African coast and 70W. Moderate to fresh NE to ENE trades and seas of 7 to 9 ft prevail across the rest of the Atlantic Basin. For the forecast, the 1001 mb low pressure is crossing Florida and will move into the Atlantic, east of northern Florida by late this afternoon. The low will then move NE to the north of the area tonight, with gale force winds developing on both sides of it for areas N of 28N and W of 71W. Frequent gusts to gale force are first expected east of Florida this afternoon. A trailing cold front will cross the region Wed through Thu, bringing scattered showers and thunderstorms with it. Building high pressure behind the low should lead toward tranquil conditions Thu night through Fri. $$ Chan