000 AXNT20 KNHC 241135 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 735 AM EDT Mon Aug 24 2020 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 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 0600 UTC surface analysis and satellite imagery through 1115 UTC. ...SPECIAL FEATURES... Tropical Storm Laura is centered near 20.8N 78.9W or about 150 nm east-southeast of Cayo Largo, Cuba and 220 nm east-southeast of the Isle of Youth moving WNW, or 295 degrees, 18 kt. The estimated minimum central pressure is 1000 mb. The maximum sustained wind speeds are 55 kt with gusts to 65 kt. Laura has acquired a well pronounced and wide banding feature that consists of numerous moderate to strong convection. This band is observed from 17N to 19N between 78W-82W and within 30 nm of a line from 19N82W to 21N82W. Scattered moderate to isolated strong convection makes up an outer band denoted by a 30 nm wide line that extends from 14N76W to 17N76W to eastern Cuba near 21N76W. Similar convection is that is within 30 nm of the center of Laura. Laura will maintain its same motion over the next couple of days, with a decrease in forward speed. A turn toward the northwest is forecast by Wed. On the forecast track, the center of Laura will move over the Caribbean Sea just offshore the southern coast of Cuba today, and move into the southeastern Gulf of Mexico by early Tuesday morning. Laura is then forecast to move over the central and northwestern Gulf of Mexico Tue night and Wed. 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 Storm Marco is centered near 27.6N 88.2W or about 100 nm south-southeast of the mouth of the Mississippi River moving northwest or 325 degrees at 9 kt. The estimated minimum pressure is 1003 mb, The maximum sustained wind speeds are 50 kt with gusts to 60 kt.Satellite imagery shows that Marco is undergoing southwesterly vertical shear and as a result is on a weakening trend as its center practically entirely exposed within 60 nm to the southwest of a large area of numerous moderate convection that exists from 28N northward to across the Florida panhandle between Apalachicola and Destin. Scattered showers and thunderstorms are seen from 29N to 30N between 88W-89W. Marco is forecast to approach the coast of Louisiana this afternoon, and then turn westward and move very close to the coast of Louisiana through Tue night. Further weakening is expected, and Marco is forecast to become a tropical depression late on Tue and dissipate on Wed. Marco is expected to produce total rainfall accumulations of 3 to 5 inches with isolated maximum amounts of 10 inches across portions of the northeast and north-central Gulf coast through Tue. This rainfall may result in areas of flash, urban and small stream flooding along the area. Please read the latest NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPAT4.shtml and Forecast/Advisory at https://www.nhc.noaa.gov/text/MIATCMAT4.shtml, for more details. The pressure gradient, that exists between a 1024 mb high pressure center that is about 800 nm to the WNW of the Canary Islands, and lower pressures over W Africa, supports gale-force winds near the Canary Islands and the regional waters. The most recent scatterometer data confirmed the gale-force winds. The Meteo-France forecast consists of a gale warning that expires at 25/0000 UTC, in the area of CANARIAS. Please refer to the Meteo- France High Seas Forecast, that is listed on the website: www.meteofrance.com/previsions-meteo-marine/bulletin/grandlarge/m etarea2, for more details. ..TROPICAL WAVES... A far eastern Atlantic tropical wave has its axis along 19W from 02N to 20N, moving westward at 10 to 15 kt. Scattered moderate to isolated strong convection is within 240 nm either side of the axis from 05N to 08N. In addition, similar convection is along inland the coast of Africa from 08N to 12N. This activity extends westward for 120 nm. A Central Atlantic tropical wave has its axis along 40W from 02N to 23N. It is moving westward at 10-15 kt. This wave is moving through a stable and dry surrounding environment. Only isolated weak showers are noted within 180 nm either side of the axis from 05N to 10N. A trough extends from near 28N51W to 20N55W and to 09N55W. Scattered showers and isolated thunderstorms are within 180 nm west of the trough from 09N to 10N and from 14N to 23N. A central Caribbean tropical wave has its axis along 77W south of 15N, moving westward at 10-15 kt. This wave bisects the eastern segment of the Pacific monsoon trough that stretches from southern Nicaragua to 11N80W and to just west of northwestern Colombia. Small isolated showers and thunderstorms are within 60 nm east of the wave south of 13N. ...MONSOON TROUGH/ITCZ... The monsoon trough axis passes through the northernmost coastal sections of Mauritania southwestward to 15N25W to 10N29N and west to 09N38W. The ITCZ axis extends from 07N42W to 09N49W and to just west of the above mentioned trough. Interestingly, for this time during the hurricane season the monsoon trough and ITCZ lack any considerable amount of convection that usually occurs there in August. Only weakening scattered moderate convection is noted within 180 nm south of the trough between 26W-34W. GULF OF MEXICO... Please see the Special Feature section above for the latest information on Tropical Storm Marco and on Tropical Storm Laura soon to enter the basin. Other than Tropical Storm Marco, generally weak high pressure is present over the area. Overnight ASCAT data shows gentle to moderate winds over just about the entire Gulf, with the exception of the areas surrounding Marco where winds are strong to near tropical Storm force, primarily north of its center and outside the tropical force wind radii. Scattered moderate to strong convection is over the Bay of Campeche south of 20N and between 92W-96W. This activity is being enhance to some extent by the northern fringe of an eastern Pacific tropical wave that is along 96W. Tropical Storm Marco centered near 27.6N 88.2W 1003 mb at 5 AM EDT is moving NW at 10 kt. Maximum sustained winds 50 kt gusts 60 kt. Marco will weaken as it reaches to near 28.06 89.2W this afternoon with maximum sustained winds 45 kt gusts 55 kt, move inland to near 29.2N 90.8W late tonight, then weaken to a tropical depression over water near 29.5N 92.7W Tue afternoon and become a remnant low and move to near 29.4N 94.5W Wed before dissipating Wed afternoon. Tropical Storm Laura centered near 20.8N 78.9W 1000 mb at 5 AM EDT is moving WNW at 18 kt. Maximum sustained winds 55 kt gusts 60 kt. Laura will move to near 21.7N 81.5W this afternoon, to near 22.9N 84.6W late tonight with maximum sustained winds 60 kt gusts 75 kt, then intensify to a hurricane as it reaches near 24.5N 87.6W Tue afternoon with maximum sustained winds 65 kt gusts 80 kt. Laura will continue to intensify as it reaches to near 26.1N 90.2W late Tue night with maximum sustained winds 75 kt gusts 85 kt, to near 28.0N 92.3W Wed afternoon with maximum sustained winds 85 kt gusts 105 kt and to near 29.8N 93.3W late Wed night. Laura will weaken to a tropical storm while moving inland to near 35.4N 91.5W early Fri. Atlantic high pressure will build westward over the eastern Gulf in the wake of Laura. CARIBBEAN SEA... Please see the Special Feature section above for the latest information on Tropical Storm Laura. Outside convection associated with Tropical Storm Laura and the tropical wave along 77W, an area of scattered isolated thunderstorms is over the eastern Caribbean south of 15N and east of 67W to the Windward Islands. Similar activity is over the far northeast part of the Caribbean to the northern Leeward Islands. Increasing activity, in the form of scattered showers and thunderstorms moving to the southwest are seen over the British and U.S. Virgin Islands to over eastern Puerto Rico. This activity is being enhanced by an upper-level low that is over the Atlantic near 22N62W. It is moving toward the west. Tropical Storm Laura centered near 20.8N 78.9W 1000 mb at 5 AM EDT is moving WNW at 18 kt. Maximum sustained winds 55 kt gusts 60 kt. Laura will move to near 21.7N 81.5W this afternoon and to the far southeastern Gulf of Mexico near 22.9N 84.6W late tonight. Laura will move farther west into the southeast Gulf of Mexico where it will intensify into a hurricane Tue afternoon and move into the north central Gulf through mid-week. ATLANTIC OCEAN... An upper-level low is near 22N62W moving westward. An upper trough extends from the low south-southeastward to 15N61W and to near 12N61W. Satellite imagery shows increasing scattered showers and thunderstorms from eastern Puerto to the U.S. and British Virgin northward to 23N and between 60W-67W. Scattered showers and isolated thunderstorms are to the northwest of this activity from 23N to 25N between 64W-69W. Isolated showers and thunderstorms are elsewhere south of 30N between 58W-70W. Scattered showers and isolated thunderstorms are quickly moving westward over the southwest part of the area south of 25N and west of 77W. This activity is being steered by strong low-level easterly flow that is a result of a tight pressure gradient between Marco and high pressure situated over the western half of the area to the north of Laura. Expect for this activity to increase further through tonight as Laura progresses west- northwestward into the southeastern Gulf of Mexico. Broad surface high pressure, anchored by 1022 mb high center at 32N72W and a 1024 mb high center at 33N33W, covers the area north of about 27N. This high pressure area will gradually shift southward late this week. Tropical Storm Laura centered near 20.8N 78.9W 1000 mb at 5 AM EDT is moving WNW at 18 kt. Maximum sustained winds 55 kt gusts 60 kt. Laura will move to near 21.7N 81.5W this afternoon and to the far southeastern Gulf of Mexico near 22.9N 84.6W late tonight. Laura will move farther west into the far southeastern Gulf of Mexico near 22.5N 82.6W Mon evening. Laura will move farther west into the southeast Gulf of Mexico where it will intensify into a hurricane and move into the north central Gulf through mid-week. $$ Aguirre