000 AXNT20 KNHC 191746 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Thu Aug 19 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 1700 UTC. ...SPECIAL FEATURES... Tropical Storm Grace, currently inland over the Yucatan Peninsula, is centered near 20.2N 88.8W at 19/1500 UTC or 75 nm W of Tulum, Mexico moving W at 16 kt. Estimated minimum central pressure is 994 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Peak seas are currently 16 ft. Scattered moderate isolated strong convection is from 17N to 23N between 84W and 91W, including portions of the NW Caribbean, S Gulf of Mexico, and E Bay of Campeche. A general westward to west-northwestward motion is expected today, followed by a general westward to west- southwestward motion at a slower speed over the weekend. On the forecast track, Grace is expected to continue to move across the Yucatan Peninsula today, and move over the southwest Gulf of Mexico late tonight through Friday. Grace will likely make a second landfall on the mainland coast of Mexico late Friday or early Saturday. Additional weakening is possible while Grace moves across land today. Re-intensification is likely after the center reaches the Gulf of Mexico. Grace is forecast to be a hurricane when it makes its second landfall on the mainland coast of Mexico late Friday or early Saturday. Rapid weakening is expected after Grace moves inland over central Mexico. 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 29.5N 70.5W at 19/1500 UTC or 700 nm S of Nantucket, Massachusetts moving W at 8 kt. Estimated minimum central pressure is 995 mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt. Peak seas are currently 25 ft. Numerous moderate isolated strong convection is from 27N to 31N between 68W and 73W. A turn toward the northwest is forecast on Friday, followed by an acceleration toward the north and north- northeast 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 southern New England on Sunday and Monday. Little change in strength is expected today, but Henri is forecast to intensify into a hurricane on Friday with additional strengthening predicted to occur 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. 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 tropical wave is along 28W from 21N southward, moving W at 10-15 kt. Scattered moderate convection is from 06N to 13N between 24W and 33W. A tropical wave is along 38W from 22N southward, moving W at 10-15 kt. Scattered moderate convection is from 05N to 10N between 38W and 43W. A tropical wave is along 58W from 22N southward, moving W at around 15 kt. Scattered moderate convection is impacting mainly the Windward Islands, southern Leeward Islands, and E Caribbean, within an area from 12N to 17N between 60W and 65W. A tropical wave is along 71W from 22N southward, moving W at around 10-15 kt. No convection is noted with the wave at this time. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of Mauritania near 17N16W to 13N28W to 09N46W. The ITCZ then extends from 09N46W to 09N56W. In addition to the convection associated with the tropical waves, scattered moderate convection is from 08N to 18N east of 20W. ...GULF OF MEXICO... Refer to the Special Features section above for details on Tropical Storm Grace, which is expected to enter the Bay of Campeche later today. Near gale to gale force E winds are affecting Gulf waters adjacent to the northern Yucatan Peninsula with SE winds of similar force in the Yucatan channel as Grace continues to move inland. Gale force N winds are in the E Bay of Campeche ahead of Tropical Storm Grace. Seas are 9-14 ft in these areas of high winds. Gentle to moderate return flow is elsewhere as the basin continue to be under the influence of surface ridging and a high pressure over the Florida Panhandle. Seas are 4-6 ft in the northern and eastern Gulf in SE to S swell. In the W Gulf, seas are 2-4 ft. For the forecast, Grace will move to 20.6N 91.2W this evening, strengthen to a hurricane near 20.6N 94.0W Fri morning, be near 20.4N 96.3W Fri evening, move inland and weaken to a tropical storm near 20.0N 98.7W Sat morning. Conditions associated with Grace will affect the Yucatan channel and region N of the Yucatan Peninsula today and the Bay of Campeche tonight through Sat. ...CARIBBEAN SEA... Refer to the Special Features section above for details on continuing impacts from Tropical Storm Grace. Strong to gale force E to SE winds persist in the W Caribbean and Yuctan Channel as Tropical Storm Grace continues inland over the Yucatan Peninsula. Seas are 10-16 ft in the far NW Caribbean, and 6-10 ft in the remainder of the W Caribbean. In the E and Central Caribbean, moderate to fresh trades prevail with 4-7 ft seas, except in the SW Caribbean where seas are 2-4 ft. Scattered moderate convection is in the SW Caribbean from 10N to 15N west of 80W. For the forecast, Grace will continue to move west of the area today, with marine conditions gradually improving through tonight. Otherwise, moderate to fresh trade winds will dominate elsewhere, except for locally fresh to strong winds in the Gulf of Honduras and south-central Caribbean through tonight. ...ATLANTIC OCEAN... Please refer to the sections above for details on Tropical Storm Henri and on the tropical waves moving across the basin. The tropical Atlantic is dominated by a 1024 mb subtropical High north of the discussion area, which has gradually been Advancing south behind Tropical Storm Henri. Gentle to moderate NE winds, becoming locally fresh east of the Lesser Antilles, Keep seas around 4-7 ft in the waters east of 60W. Winds veer to SE north of 23N between 60W and 70W as the flow begins to enter Tropical Storm Henri's circulation. Farther west, at 1500 UTC the ASCAT data depicated a 1021 mb high near 30N80W, producig gentle Flow across waters west of 75W. Seas are 2-4 ft near and W of the Bahamas. East of the Bahamas, seas build to 10-15 ft near Henri. For the forecast, Henri will move to 29.7N 71.9W this evening, 30.4N 72.9W Fri morning, strengthen to a hurricane near 31.9N 72.9W Fri evening, 34.4N 72.0W 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 N of Hispaniola and the approaches to the Windward Passage. $$ Mahoney