000 AXNT20 KNHC 202315 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Wed Jul 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Caribbean Gale Warning: The pressure gradient between the Atlantic ridge and the Colombian/Panamanian low will support gale force winds off the coast of the Colombia and in the Gulf of Venezuela tonight, and again Wed night. Seas are forecast to build up to 12-14 ft with the strongest winds across the south-central Caribbean. For more information, please see the High Seas Forecast issued by the National Hurricane Center at https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml ...TROPICAL WAVES... An Atlantic tropical wave extends its axis along 27W and south of 21N, moving west at 10 to 15 kt. Scattered moderate convection is noted where the wave meets the monsoon trough from 07N to 11N between 26W and 31W. A second tropical wave extends it axis along 48W from 20N southward, moving westward at 10 to 15 kt. Subsidence and dry air associated with the Saharan Air Layer surrounds the wave. A third tropical wave is along 87W and south of 18N crossing northern central America. This tropical wave is moving west at 10 to 15 kt. The wave is helping to induce scattered showers and thunderstorms over parts of Belize, northern Guatemala and the Yucatan Peninsula. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic Ocean through Senegal and extends from 13N17W to 10N30W to 09N45W. The ITCZ extends from 07N50W to the coast of Guyana near 07N58W. Scattered moderate to isolated strong convection is noted from 05N to 10N between 13W and 21W. GULF OF MEXICO... A surface trough is over the NW Gulf and extends from SE Louisiana to south Texas. Scattered to numerous showers and thunderstorms are noted ahead of the trough axis. Moderate to fresh winds are behind the trough. Showers and thunderstorms are also noted over most of Florida. The remainder of the Gulf is under the influence of the Atlantic ridge that extends westward across Florida into the eastern Gulf producing light to gentle anticyclonic flow. Seas are in the 1-3 ft range across the entire basin, however winds and seas could be higher near thunderstorms. For the forecast, a ridge will continue to dominate the Gulf waters producing gentle to moderate winds the rest of the work- week. The exception will be moderate to fresh NE-E winds to the west of the Yucatan Peninsula Wed night through Fri night due to local effects induced by a thermal trough. CARIBBEAN SEA... A Gale Warning is in effect for the south-central Caribbean. Please, see the Special Features section for details. The most recent scatterometer data depict fresh to strong trades prevailing across most of the central Caribbean with seas of 8-10 ft. Buoy 42058 is reporting combined seas of 9 ft. Elsewhere in the basin, moderate to fresh trades prevail with 5-8 ft seas, except in the NW Caribbean where trades are gentle to moderate with 2-4 ft seas. For the forecast, the aerial extent and strength of the trades will increase beginning tonight. Fresh to strong winds will reach as far north as Hispaniola adjacent waters. Fresh NE winds are expected in the Windward Passage through Thu night. Fresh to strong winds are forecast to pulse in the Gulf of Honduras Wed night and Thu night with seas building to 6-7 ft. Under the influence of this trade wind surge propagating across the Caribbean, conditions appear fairly favorable for heavy rainfall amounts over southern Central America over the next few days. The onset of the activity is expected late on Wed, and will likely peak Thu through Sat. In fact, the GFS model suggests abundant tropical moisture in a NE winds flow from Nicaragua to Panama and western Colombia late on Wed. A pair of tropical waves are between the west coast of Africa and the Lesser Antilles. Please refer to the Tropical Wave section above for details. A 1026 mb high pressure located E of Bermuda near 32N53W extends a ridge across the Bahamas and Florida into the eastern gulf Of Mexico. Scattered moderate convection is noted E of Florida and N of the NW Bahamas ahead of a frontal boundary that crosses the SE of United States. Mainly patches of low level clouds are seen over the remainder of the ocean. Another high pressure center is located just N of the Madeira Islands. Fresh to strong northerly winds are noted per scatterometer data near the coast of Morocco where seas are in the 6-8 ft range. Moderate to fresh N to NE winds are seen across the Canary islands, and from 20N-30N E of of 30N. Seas are generally in the 5-7 ft range within these winds. Similar wave heights are also noted between 50W and the Lesser Antilles. For the forecast W of 65W, high pressure will be in control of the weather pattern across the region. Fresh to strong easterly winds will pulse just off north of Hispaniola, including the approach to the Windward passage in the late afternoon and evening hours for the next several days. $$ GR