000 AXNT20 KNHC 180610 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 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 0000 UTC surface analysis and satellite imagery through 0600 UTC. ...SPECIAL FEATURES... Tropical Storm Grace is centered near 18.7N 80.1W at 18/0600 UTC or 75 nm ESE of Grand Cayman, Cayman Islands. Grace is moving W at 12 kt and the estimated minimum central pressure is 1000 mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt. Grace is producing a large area of showers and thunderstorms, especially over the eastern semicircle. The convection extends from 15N to 20N and between 75W and 81W. Peak seas near the center are currently in the 17-20 ft range. A general westward to west- northwestward motion is expected for the next several days. On the forecast track, the center of Grace will continue to move away from the western coast of Jamaica overnight. Grace is forecast to move near or over the Cayman Islands early Wednesday, and then approach the Yucatan peninsula of Mexico late Wednesday or early Thursday. Grace is forecast to strengthen into a hurricane on Wednesday, with some additional strengthening possible prior to the center reaching the Yucatan Peninsula. 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 30.0N 65.1W at 18/0600 UTC or 140 nm S of Bermuda. Henri is moving WSW at 5 kt and the estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Henri is a small tropical storm, and the scattered moderate to isolated strong convection is noted from 28N to 31N and between 61W and 66W. Peak seas near the center are currently in the 12-15 ft range. A gradual turn to the west with a faster forward motion is expected over the next 12 to 24 hours, followed by an additional turn to the west-northwest and northwest by late Thursday. Some additional strengthening is possible tonight, followed by little change in strength through Thursday. 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... An Atlantic tropical wave has its axis along 23W, south of 20N and it is moving W at around 10 kt. Scattered moderate convection is noted near the wave axis from 14N to 17N. A second Atlantic wave has its axis along 44W, south of 21N and it is moving W at around 15 kt. No significant convection is noted with this wave. A third Atlantic wave has its axis along 61W, near the Lesser Antilles, south of 21N, and it is moving W at around 15 kt. Scattered moderate convection is noted within 100 nm of the wave axis from 09N to 12N. A Caribbean tropical wave has its axis along 89W, south of 19N and it is moving W at 10-15 kt. This wave is enhancing convection on the Pacific coast of W Central America. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from Mauritania near 17N16W to 15N25W, to 12N34W and to 07N43. The ITCZ then extends from 07N44W to 08N54W. Aside from the convection associated with the tropical waves, scattered moderate convection is seen south of the monsoon trough from 04N to 10N between 20W to 40W. Strong convection is also noted within 150 nm of the coast of Africa from 10N to 17N. ...GULF OF MEXICO... Fairly tranquil weather conditions prevail across the Gulf of Mexico. A weak surface trough was analyzed at 0000 UTC in the Bay of Campeche, but has dissipated as of 0300 UTC. Moderate to fresh E-NE winds are noted in recent scatterometer satellite data in the SE Gulf waters off the NW coast of Cuba to the Florida Straits, and N and W of the Yucatan peninsula. Gentle to moderate anticyclonic winds elsewhere in the basin. Seas are 2-4 ft in the Gulf. For the forecast, Tropical Storm Grace over the Caribbean Sea near 18.4N 79.2W 1000 mb at 11 PM EDT moving W at 12 kt. Maximum sustained winds 50 kt gusts 60 kt. Grace will move to near 18.9N 81.5W early Wed morning, then strengthen to a hurricane near 19.5N 84.7W Wed evening with maximum sustained winds 75 kt gusts 90 kt. Grace will move inland the Yucatan Peninsula near 20.0N 87.8W early Thu, and weaken to a tropical storm near 20.4N 90.7W Thu evening with maximum sustained winds 50 kt gusts 60 kt, re- strengthen to a hurricane near 20.7N 93.2W early Fri with maximum sustained winds 65 kt gusts 80 kt, reach to near 20.8N 95.6W Fri evening and weaken to a tropical storm while moving inland near 20.7N 100.1W late Sat. Winds and seas will begin to increase across the southeastern Gulf ahead of Grace on Wed. 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 Tropical Storm Grace. Scattered moderate to isolated strong convection is noted within 100 miles of the NW coast of Colombia and between the Cayman islands and W Cuba. 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. Seas are 5-7 ft in the central and E Caribbean. Seas are 3-5 ft in the NW Caribbean and 1-3 ft in the remainder of the basin. For the forecast, Tropical Storm Grace near 18.4N 79.2W 1000 mb at 11 PM EDT moving W at 12 kt. Maximum sustained winds 50 kt gusts 60 kt. Grace will move to near 18.9N 81.5W early Wed morning, then strengthen to a hurricane near 19.5N 84.7W Wed evening with maximum sustained winds 75 kt gusts 90 kt, and move inland the Yucatan Peninsula near 20.0N 87.8W early Thu. 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. An expansive 1027 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 6-9 ft range. Recent scatterometer satellite data detected fresh to locally strong NE winds from 19N to 30N and between 27w and 47W, and seas are in the 3-6 ft range. Moderate to fresh E winds are found south of 19N between 40W 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 65.1W 998 mb at 11 PM EDT moving WSW at 7 kt. Maximum sustained winds 55 kt gusts 65 kt. Henri will strengthen slightly as it moves to near 29.9N 66.0W Wed morning with maximum sustained winds 60 kt gusts 75 kt, then maintain intensity as it moves to near 29.8N 67.7W Wed evening, to near 29.8N 69.5W Thu morning, to near 30.1N 71.1W Thu evening, to near 30.9N 72.0W Fri morning, and strengthen to a hurricane near 32.0N 71.9W Fri evening with maximum sustained winds 70 kt gusts 85 kt. Fresh east to southeast winds over the far southwest part of the area will shift W to the Straits of Florida Wed night. Otherwise, high pressure will persist across the forecast waters through the period. $$ DELGADO