000 AXNT20 KNHC 172300 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Wed Aug 18 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 2245 UTC. ...SPECIAL FEATURES... Tropical Storm Grace is centered near 18.4N 77.9W at 17/2100 UTC or 0 nm S of Montego Bay Jamaica moving W at 13 kt. Estimated minimum central pressure is 1003 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. SCattered to numerous moderate convection prevails from 15N-22N between 73W-82W. Peak seas are currently at 16 ft. On the forecast track, the center of Grace will continue to move near the northwestern coast of Jamaica for the next few hours. Grace is forecast to move near or over the Cayman Islands late tonight and early Wednesday, and then approach the Yucatan peninsula of Mexico late Wednesday or early Thursday. Please read the latest NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPAT2.shtml and Forecast/ Advisory at https://www.nhc.noaa.gov/text/MIATCMAT2.shtml for more details. Tropical Storm Henri is centered near 30.4N 64.2W at 17/2100 UTC or 120 nm SSE of Bermuda moving WSW at 2 kt. Estimated minimum central pressure is 997 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Scattered moderate convection is from 28N-31N between 61W-66W. Maximum seas will reach 15 ft. A faster motion toward the west is forecast by tonight, followed by a motion to the west-northwest or northwest by late Thursday. On the forecast track, the center of Henri should pass well to the south of Bermuda through tonight. Please read the latest NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPAT3.shtml and Forecast/Advisory at https://www.nhc.noaa.gov/text/MIATCMAT3.shtml for more details. ...TROPICAL WAVES... A far eastern Atlantic tropical wave extends its axis along 22N from 03N to 20N, moving westward at 10-15 kt. Scattered moderate convection is noted from 04N to 16N between 20W and 27W. An eastern Atlantic tropical wave has its axis along 42W from 02N to 21N, moving westward near 15 kt. Scattered showers are noted in the vicinity of the wave. A central Atlantic tropical wave has its axis along 59W from 20N southward to inland Guyana, moving westward at 10-15 kt. Scattered showers and thunderstorms are noted south of 11N between 58W to 62W. A western Caribbean tropical wave has its axis along 88W from 19N southward, moving westward at 10-15 kt. Scattered showers and thunderstorms are noted on the southern end of the wave axis over the eastern Pacific. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from Senegal near 13N17W to 08N44W, then transitions to ITCZ from 08N44W to 08N53W. Aside from the convection associated with the tropical waves, scattered moderate convection is seen south of the monsoon trough from 02N to 10N between 41W-36W. ...GULF OF MEXICO... With Tropical Depression Fred continuing to move farther inland, the gradient is relaxed over the Gulf of Mexico. Light and gentle winds prevail across the basin, with seas of 2 to 3 ft. A surface trough continues over the Bay of Campeche. No significant convection is noted with the trough at this time. Tropical Storm Grace will move to 18.9N 80.3W Wed morning, strengthen to a hurricane near 19.4N 83.4W Wed afternoon, 20.0N 86.7W Thu morning, move inland and weaken to a tropical storm near 20.5N 89.7W Thu afternoon, strengthen to a hurricane near 20.9N 92.2W Fri morning, and 21.2N 94.8W Fri afternoon. Grace will weaken to a tropical storm while moving inland near 21.0N 99.5W Sat afternoon. Grace is forecast to move near or over the Cayman Islands late tonight and early Wednesday, and then approach the Yucatan peninsula of Mexico late Wednesday or early Thursday. Winds and seas will begin to increase across the SE waters ahead of Grace on Wed. ...CARIBBEAN SEA... Refer to the Special Features section above for details on Tropical Storm Grace. Outside of the wind field of Grace, latest ASCAT data passes showed moderate to fresh winds in the eastern and central Caribbean and light to gentle trades in the western Caribbean, pulsing to moderate in the Gulf of Honduras. Seas are 5-7 ft in the east-central Caribbean, 4-6 ft near the Windward Islands, 3-5 ft near the Leeward Islands and in the west-central Caribbean, and 3 ft or less in the western Caribbean. For the forecast, Tropical Storm Grace will move to 18.9N 80.3W Wed morning, strengthen to a hurricane near 19.4N 83.4W Wed afternoon, 20.0N 86.7W Thu morning, move inland and weaken to a tropical storm near 20.5N 89.7W Thu afternoon, strengthen to a hurricane near 20.9N 92.2W Fri morning, and 21.2N 94.8W Fri afternoon. Grace will weaken to a tropical storm while moving inland near 21.0N 99.5W Sat afternoon. Grace is forecast to move near or over the Cayman Islands late tonight and early Wednesday, and then approach the Yucatan peninsula of Mexico late Wednesday or early Thursday. Elsewhere, fresh to strong trades will be over the central Caribbean through Wed night. ...ATLANTIC OCEAN... Please refer to the sections above for details on Tropical Storm Henri an the tropical waves moving across the basin. The tight pressure gradient in the eastern Atlantic near the Canary Islands continues to support near gale force NE winds, which were detected by the latest scatterometer pass. Seas 6-9 ft are noted in the areas of strongest wind. Elsewhere, surface ridging and a weak pressure gradient prevails. Fresh trades are noted from the Turks and Caicos south to the coast of Hispaniola, and in the Windward Passage with seas of 3-6 ft. Gentle to moderate E to SE winds are over the western Atlantic, including the Bahamas and areas north of Turks and Caicos. Light winds are north of 20N between 40W and 70W excluding the area near the Tropical Storm Henri. Gentle to moderate trades are south of 24N in the remainder of the basin, except moderate to fresh NE winds north of 25N east of 20W. Seas are generally 3-6 ft across the basin, with the highest seas near Hispaniola and southeastern Bahamas. For the forecast west of 65W, Tropical Storm Henri will move to 30.3N 65.5W Wed morning, 30.2N 67.0W Wed afternoon, 30.2N 68.6W Thu morning, 30.3N 70.0W Thu afternoon, 31.0N 71.1W Fri morning, and strengthen to a hurricane near 32.0N 71.5W Fri afternoon. Henri will change little in intensity as it moves to near 35.5N 69.6W Sat afternoon. On the forecast track, the center of Henri should pass well to the south of Bermuda through tonight. Elsewhere, high pressure will persist across the forecast waters through the period. $$ ERA