627 AXNT20 KNHC 200603 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 UTC Fri Aug 20 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 0550 UTC. ...SPECIAL FEATURES... Tropical Storm Grace is centered near 20.8N 92.6W at 20/0600 UTC or 270 nm E of Tuxpan, Mexico. It is moving W at 14 kt and the estimated minimum central pressure is 994 mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt. Peak seas are currently 23 ft near the center of Grace. Showers and thunderstorms have increased during the past few hours over the center of Grace as the storm reorganizes in the E Bay of Campeche after crossing the Yucatan Peninsula. Scattered moderate isolated strong convection is from 19N to 22N and between 90W and 95W. A general westward motion is expected early this morning, followed by a westward to west-southwestward motion at a slower speed beginning later today. On the forecast track, the center of Grace is forecast to move across the southwestern Gulf of Mexico today, and then make landfall along the coast of mainland Mexico this evening or tonight. Additional strengthening is likely until Grace makes landfall, and the system is expected to regain hurricane strength later this morning. After landfall, Grace should weaken rapidly as it moves into the mountains of central Mexico. Seas will increase as the system moves across the Bay of Campeche, reaching up to 36 ft tonight. 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 29.8N 72.3W at 20/0300 UTC or 360 nm SSE of Cape Hatteras, North Carolina. It is moving W at 7 kt with an estimated minimum central pressure of 997 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Peak seas are currently 22 ft. Northerly wind shear continues to affect the tropical storm, causing most of the convection to be located in the southern semicircle. Numerous showers and thunderstorms are noted from 26N to 31N and between 70W to 75W. A sharp turn to the northwest and north is anticipated on Friday, followed by an acceleration to the north and north-northeast on Saturday and Sunday. On the forecast track, the center of Henri will remain well offshore of the east coast of the United States over the next couple of days, but it is forecast to be near or over southern New England on Sunday and Monday. Little change in strength is expected during the next 12 hours, but Henri is forecast to intensify into a hurricane by Friday night with additional strengthening expected this weekend. Swells generated by Henri should continue to affect Bermuda during the next day or so. Swells are expected to increase across much of the east coast of the U.S. and Atlantic Canada later this week and this weekend. These swells could cause life- threatening surf and rip current conditions. 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 30W, south of 21N, and it is moving W at 10-15 kt. Scattered moderate convection is noted mainly ahead of the wave axis from 09N to 15N and between 30W and 36W. Another Atlantic tropical wave has its axis along 41W, south of 21N, and it is moving W at 10-15 kt. Scattered moderate convection is on either side of the wave axis from 07N to 14N and between 36W and 47W. A third Atlantic tropical wave has its axis along 61W, near the Lesser Antilles, south of 21N, and it is moving W at around 15 kt. A few showers are noted in the E Caribbean near and ahead of the wave axis from 15N to 18N. Moisture associated with this wave will continue to impact the eastern Caribbean and parts of the Lesser Antilles today. A Caribbean tropical wave has its axis along 73W, extending from the E Bahamas to Colombia. It is moving W at 10-15 kt. The southern portion of the wave and the Caribbean extension of the E Pacific monsoon are likely enhancing the showers and thunderstorms over N Colombia and W Venezuela, including Lake Maracaibo. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of Mauritania near 20N16W to 12N32W and to 10N51W. The ITCZ then extends from 10N52W to 07N58W. In addition to the convection associated with the tropical waves, scattered moderate convection is observed from 11N to 15N and between the coast of Africa to 21W. ...GULF OF MEXICO... Refer to the Special Features section above for details on Tropical Storm Grace. Outside of the influence of Tropical Storm Grace, fairly tranquil weather conditions are observed across the Gulf of Mexico. A recent scatterometer satellite pass depict strong to near gale- force winds associated with the circulation of Grace from 23N to 25N and roughly between 88W and 94W. Seas are 10-15 ft in this area of high winds. Fresh to strong winds are also noted in central and W Gulf, south of 26N, with seas of 6-10 ft. Moderate to fresh winds are found in the NW Gulf with seas of 3-6 ft. Lastly, a weak ridge in the NE Gulf is allowing gentle to moderate breezes and seas of 1-3 ft in the area. For the forecast, Tropical Storm Grace near 20.8N 91.8W 994 mb at 11 PM EDT moving W at 14 kt. Maximum sustained winds 55 kt gusts 65 kt. Grace will strengthen to a hurricane near 20.8N 93.7W Fri morning, move to 20.7N 95.9W Fri evening, move inland and weaken to a tropical storm near 20.1N 98.2W Sat morning, weaken to a remnant low near 19.6N 100.5W Sat evening, and dissipate Sun morning. High pressure will build in the wake of Grace and prevail through early next week. ...CARIBBEAN SEA... Scatterometer satellite data show fresh to strong trades affecting the south-central Caribbean Sea, especially off the NW coast of Colombia and the Gulf of Venezuela. Tropical Storm Grace continues to move away from the Caribbean, but the scatterometer data also depict fresh to strong E-SE winds in the Gulf of Honduras, and these winds likely extend into the NW Caribbean, west of 84W. Moderate to fresh trades prevail in the rest of the central and E Caribbean. Seas in the NW Caribbean are 4-7 ft, while 3-6 ft are prevalent in the central and E Caribbean and 2-4 ft in the SW Caribbean. Scattered showers and thunderstorms are noted W of 79W to the coast of Nicaragua and from 11N to 16N. For the forecast, Grace will continue to move west of the area this evening, with marine conditions gradually improving. Otherwise, moderate to fresh trade winds will dominate elsewhere, except for locally fresh to strong winds in the Gulf of Honduras tonight, and in the central Caribbean early next week. ...ATLANTIC OCEAN... Refer to the Special Features section above for details on Tropical Storm Henri. Three tropical waves are moving westward between the W coast of Africa and the Lesser Antilles. Please, see Tropical Waves section for details. Tropical Storm Henri is the only source of deep convection noted across the tropical Atlantic as the basin remains under the control of a broad 1024 mb subtropical ridge. The tight pressure gradient previously present in the E Atlantic has relaxed, allowing for moderate to fresh N-NE winds in the waters surrounding the Canary Islands and off the NW coast of Africa. Seas in this region are in the 6-9 ft range. Another area of moderate to fresh easterlies is observed in recent scatterometer data from 18N to 28N and between 35W to 62W. Seas in the area are in the 5-8 ft range. Moderate to fresh trades are also noted north of Puerto Rico and Hispaniola, with seas of 4-7 ft. Gentle to moderate easterly winds prevail in the rest of the basin with seas of 3-6 ft. For the forecast, Tropical Storm Henri near 29.8N 72.3W 997 mb at 11 PM EDT moving WNW at 7 kt. Maximum sustained winds 55 kt gusts 65 kt. Henri will move to 30.3N 73.2W Fri morning, move north of the area to 31.8N 73.3W Fri evening, and strengthen to a hurricane near 34.4N 72.2W Sat morning. Otherwise, moderate to fresh E to SE winds will prevail E and across the Bahamas Fri through Mon, except for fresh to locally strong winds at night north of Hispaniola and the approaches to the Windward Passage. $$ DELGADO