478 AXNT20 KNHC 171804 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Sat Jul 17 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. ...TROPICAL WAVES... An Atlantic tropical wave is near 34W from 21N southward and moving W at 5 to 10 kt. This wave remains embedded in the Saharan Air Layer, which dust and dry air is limiting the convection to scattered moderate from 03N to 07N between 28W and 34W. Another Atlantic tropical wave is just E of the Lesser Antilles along 59W from 20N southward, and moving W near 10 kt. This wave is at the western edge of the Saharan Air Layer, and only isolated showers and thunderstorms are observed over the Windward and southern Leeward Islands. A third tropical wave over the western Caribbean is near 79W from 16N southward across Panama, and moving W near 15 kt. Moderate vertical shear is enhancing scattered showers and isolated thunderstorms over Panama, and the E coast of Honduras and Nicaragua. ...MONSOON TROUGH/ITCZ... A monsoon trough extends through the Gambia coast at 12N16W to 06N37W. Then ITCZ continues from 06N37W to 05N48W, just E of Suriname-Brazil border. Scattered moderate to isolated strong convection is seen from 04N to 11N between the African coast and 28W. ...GULF OF MEXICO... An upper-level trough extending northward from the Bay of Campeche across the N Gulf continues to trigger scattered showers and isolated thunderstorms near New Orleans from 28N to 30N between 87W and 90W. Coupling with a surface trough over the Bay of Campeche, scattered showers and thunderstorms are occurring at the central Gulf and Yucatan Peninsula; including the Yucatan Channel. Locally moderate to fresh winds and seas at 3 to 5 ft are possible in these thunderstorms. Otherwise, a surface ridge extending southwestward from the Bermuda High across N Florida and the N Gulf is supporting light to gentle ESE to SE winds and seas of 1 to 3 ft across the Gulf. For the forecast, the Bermuda High extends a ridge southwestward across the SE CONUS. As the ridge sinks southward during the next few days, tranquil conditions will prevail across the Gulf of Mexico. No tropical cyclone activity is expected over Gulf through at least Wed night. ...CARIBBEAN SEA... Enhanced by modest vertical wind shear, convergent trade winds are producing scattered showers and isolated thunderstorms over western Cuba and the central W basin. Refer to the Tropical Waves section above for additional convection in the basin. Tight pressure gradient between the Atlantic ridge and the Colombian low continues to create fresh to strong trades and seas of 8 to 11 ft across the central and S central Caribbean. Gentle to moderate trades and seas of 2 to 4 ft are seen along the W Caribbean. Moderate to locally fresh trades and seas of 4 to 6 ft prevail across the rest of the basin. For the forecast, the Bermuda High north of the area and lower pressure over N Colombia continue to support fresh to strong NE to E trades over the S central and SW Caribbean. These winds will continue through early next week and increase in speed and areal coverage Mon night through Wed night, reaching Hispaniola adjacent waters. Elsewhere, NE trades will become fresh to strong tonight and Sun night in the Windward Passage. No tropical cyclone activity is expected over the Caribbean or tropical N Atlantic through at least Wed night. ...ATLANTIC OCEAN... An upper-level low SW of Bermuda near 29N69W is triggering scattered showers N of 25N between 63W and 72W. A surface trough extends southwestward from a low W of Bermuda to near the NW Bahamas at 28N77W. Scattered showers and isolated thunderstorms are occurring across S Florida and the NW Bahamas. Refer to the Tropical Waves and Monsoon Trough/ITCZ sections above for additional convection across the Atlantic. The persistent surface ridge across the central Atlantic is sustaining light to gentle winds and seas of 2 to 4 ft N of 24N between 28W and the Georgia-Florida coastline. Moderate to locally fresh trades and seas of 4 to 6 ft are present from 12N to 24N between 24W and the Lesser Antilles, and also near the Canarias Islands N of 23N between the NW African coast and 20W. Gentle to moderate trades and seas of 3 to 5 ft prevail for the rest of the Atlantic. For the forecast W of 45W, fresh to strong E winds will occur afternoons and early evenings north of Hispaniola for the next several days. Ridging associated with a weak Bermuda High will slowly sink southward to 27N by Wed, leading toward quiescent conditions across the remainder of the SW N Atlantic waters. No tropical cyclone activity is expected in the area through at least Wed night. $$ Chan