000 AXNT20 KNHC 181751 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 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 1200 UTC surface analysis and satellite imagery through 1720 UTC. ...SPECIAL FEATURES... Hurricane Grace is centered near 19.6N 83.0W at 18/1800 UTC or 255 nm E of Tulum, Mexico. Grace is moving WNW at 13 kt and the estimated minimum central pressure is 995 mb. Maximum sustained wind speed is 65 kt with gusts to 80 kt. Satellite imagery shows numerous moderate to isolated strong convection from 17N to 21N between 78W-84W. Peak seas near the center are currently in the 17-20 ft range. A general west-northwestward to westward motion is expected for the next several days. On the forecast track, Grace is expected to make landfall in the eastern Yucatan Peninsula Thursday morning, move over the Yucatan Peninsula on Thursday, and move over the southwest Gulf of Mexico Thursday night or early Friday. Some strengthening is forecast before the center of Grace reaches the Yucatan Peninsula. Weakening will occur while the center moves over the Yucatan Peninsula on Thursday, with restrengthening expected when Grace moves over the southwest Gulf of Mexico on Friday. 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 30N 66.6W at 11/1500 UTC or 165 nm south-southwest of Bermuda. Henri is moving W at 7 kt and the estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Henri remains a small tropical storm. Satellite imagery shows numerous moderate convection from 28N to 31N between 65W-68W. Peak seas near the center are currently at 17 ft. A turn to the north is expected on Friday with that motion continuing into the weekend. Little change in strength is forecast during the next couple of days, but Henri is expected to become a hurricane by the weekend. 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 has its axis along 30W from 19N southward, moving westward at around 10 kt. Scattered moderate convection is seen from 02N to 14N between 25W-35W. A central Atlantic wave has its axis along 49W south of 20N, moving westward at 15 kt. Scattered showers are possible near the wave axis. A tropical wave over the eastern Caribbean has its axis along 63W from 20N southward, moving westward at 15 kt. Scattered moderate convection is noted in the southern end of the wave from the coast of Venezuela to 12N and between 62W to 65W. The earlier analyzed western Caribbean tropical wave has moved well inland over Central America, with its southern portion over the eastern Pacific. Please refer to the eastern Pacific Tropical Weather Discussion for details on this tropical wave. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from Senegal near 12N16W to 11N30W to 08N49W. The ITCZ then extends from 08N49W to 10N61W. Aside from the convection associated with the tropical waves along 26W, scattered moderate convection is seen from 05N to 19N and east of 22W inland to the coast of Africa, from 03N to 13N between 35W to 45W, and along the ITCZ from 06N to 11N between 52W and the ABC Islands. ...GULF OF MEXICO... Fairly tranquil weather conditions prevail across the Gulf of Mexico. Moderate to fresh northeast to east winds are over the SE Gulf waters off the NW coast of Cuba to the Florida Straits, and N and W of the Yucatan peninsula. Southeast moderate to fresh winds across the western Gulf from the Bay of Campeche to Southeast Texas. Elsewhere, light and gentle winds prevail in the basin north of 24N with seas between 2-4 ft across the basin. For the forecast, Hurricane Grace near 19.4N 82.2W 992 mb at 11 AM EDT moving WNW at 13 kt. Maximum sustained winds 65 kt gusts 80 kt. Grace will move to 19.7N 84.5W this evening, inland to 20.3N 87.6W Thu morning, weaken to a tropical storm near 20.6N 90.5W Thu evening, strengthen to a hurricane near 20.7N 93.2W Fri morning, 20.7N 95.3W Fri evening, and move inland and weaken to a tropical storm near 20.5N 97.7W Sat morning. Winds and seas will begin to increase across the southeastern Gulf ahead of Grace today. These conditions will shift to west of 90W Thu through late Fri night. ...CARIBBEAN SEA... Refer to the Special Features section above for details on Hurricane Grace. Scattered moderate to strong convection is noted in the Yucatan Channel and in the northeast coast of Honduras. Outside of the wind field of Tropical Storm Grace, recent scatterometer satellite data show strong to near gale-force trade in the south-central Caribbean Sea, especially within 90 nm of the NW coast of Colombia and the Gulf of Venezuela. Fresh to strong trades are noted in the rest of the central and E Caribbean. Gentle to moderate trades are found in the rest of the basin. Latest observations indicate seas are 5-7 ft in the central and E Caribbean, 3-5 ft in the NW Caribbean and 1-3 ft in the remainder of the basin. For the forecast, Grace will move to 19.7N 84.5W this evening, inland to 20.3N 87.6W Thu morning, weaken to a tropical storm near 20.6N 90.5W Thu evening, strengthen to a hurricane near 20.7N 93.2W Fri morning, 20.7N 95.3W Fri evening, and move inland and weaken to a tropical storm near 20.5N 97.7W Sat morning. Elsewhere, fresh to strong trades will be over the central Caribbean through early Thu. ...ATLANTIC OCEAN... Please refer to the sections above for details on Tropical Storm Henri and on the tropical waves moving across the basin. An expansive 1028 mb Azores ridge dominates the tropical Atlantic, resulting in fairly tranquil weather conditions. The strong high pressure system and lower pressures over NW Africa result in a tight pressure gradient over the NE Atlantic. Strong to near gale-force N-NE winds are found surrounding the Canary Islands and off the coasts of Morrocco and Western Sahara. Seas in this area are in the 4-6 ft range. Overnight scatterometer satellite data detected fresh to locally strong NE winds from 16N to 30N and between 30W and 50W, and seas are in the 3-6 ft range. Moderate to fresh E winds are found south of 15N between 30W to the Lesser Antilles, and north of the Greater Antilles to 22N. Gentle to moderate anticyclonic winds and seas of 1-3 ft are prevalent in the rest of the basin. For the forecast west of 65W, Tropical Storm Henri near 30.0N 66.6W 998 mb at 11 AM EDT moving W at 7 kt. Maximum sustained winds 55 kt gusts 65 kt. Henri will move to 29.9N 67.9W this evening, 29.8N 69.8W Thu morning, 30.1N 71.4W Thu evening, 30.7N 72.4W Fri morning, strengthen to a hurricane near 32.1N 72.5W Fri evening, and 34.2N 71.5W Sat morning. Elsewhere, high pressure will persist across the forecast waters through the period. Fresh east to southeast winds over the far southwest part of the area will shift W to the Straits of Florida tonight. $$ MTorres