000 AXNT20 KNHC 231140 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 740 AM EDT Sun Aug 23 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 1130 UTC. ...SPECIAL FEATURES... Tropical Storm Laura is centered near 18.8N 70.9W or about 80 nm east of Port Au Prince Haiti or about 95 nm southeast of Cap Haitien, Haiti at 23/0900 UTC. Laura is moving WNW, or 285 degrees at 16 knots. The estimated minimum central pressure is 1005 mb. The maximum sustained wind speeds are 40 knots with gusts to 50 knots. Satellite imagery shows a quite impressive large and symmetrical cloud pattern with Laura that consists of numerous moderate to strong type convection within 180 nm of the center in the SW quadrant, within 150 nm of the center in the SE quadrant and within 90 nm of the center in the N semicircle. Scattered moderate to isolated strong convection is within 30 nm of line from 18N74W to 19N75W. This observed convection acquired very cold cloud top temperatures during the night while the center remains over land. Laura is forecast to maintain its current motion during the next few days. On the present forecast track, the center of Laura will move across Hispaniola today, be near or over Cuba tonight and Mon, and over the southeastern Gulf of Mexico Mon night and Tue. Swells generated by Laura are affecting portions of the Virgin Islands, Puerto Rico, and Hispaniola. These swells are expected to spread across Cuba, much of the Bahamas, and the Florida Keys during the next few days. Please consult products from your local weather office. 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 23.7N 87.0W or about 160 nm NW of the western tip of Cuba or 340 nm south-southeast of the mouth of the Mississippi River at 23/0900 UTC. Marco is moving NNW, or 335 degrees at 11 kt. The estimated minimum central pressure is 994 mb. The maximum sustained wind speeds are 55 knots with gusts to 65 knots. Numerous moderate to strong convection in a CDO pattern is seen within 150 nm of the center in the NE quadrant and in an outer wide band from 22N to 24N between 85W- 87W. Scattered moderate to isolated strong convection is within 30 nm of line from 24N83W to 26N85W and to 26N86W. Marco is forecast to continue moving north-northwestward across the central Gulf of Mexico today and will approach southeastern Louisiana on today. A gradual turn toward the west with a decrease in forward speed is expected after Marco moves inland on Mon and on Tue. Marco is expected to produce rainfall accumulations of 2 to 4 inches with isolated maximum amounts of 6 inches across the Central U.S. Gulf coast through Tue. This rainfall may result in isolated areas of flash and urban flooding along the Central U.S. Gulf Coast. 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. ..TROPICAL WAVES... A far eastern Atlantic tropical wave has its axis along 32W from 02N to 21N, moving westward at 10-15 knots. A rather dry and stable environment surrounds this wave. Weak small isolated showers and thunderstorms are within 60 nm of the wave axis from 05N to 09N. A short-amplitude Caribbean tropical wave has its axis along 71W south of 15N, moving westward at about 10 kt. Only isolated showers and thunderstorms are noted near this wave. A western Caribbean tropical has its axis along 79W south of 19N. It is moving westward at 15 knots. The monsoon trough is along 11N73W in NE Colombia near the border with Venezuela, to 12N80W, to 13N85W in Nicaragua, and westward, through Honduras, El Salvador, and Guatemala, into the eastern Pacific Ocean. Scattered showers and isolated thunderstorms are south of the monsoon trough. The previous tropical wave that was along 91W south of 17N is now being described in the Eastern Pacific Tropical Weather Discussion. ...MONSOON TROUGH/ITCZ... The monsoon trough axis passes through the coastal sections of Mauritania near 18N16W to 18N20W to 16N22W to 11N24W to 11N35W and to 09N50W, where latest scatterometer data indicates that it transitions to the ITCZ and extends to near the coast of Venezuela at 10N61W. Scattered moderate convection is along and within 60 nm south of the ITCZ west of 58W. Otherwise, the ITCZ is devoid of deep convection for the time being. GULF OF MEXICO... Please see the Special Features section above for details on Tropical Storm Marco. Other than Tropical Storm Marco, relatively weak high pressure is present over the basin. Scattered moderate to isolated strong convection is seen along the coast and inland Mexico from 91W-96W. Similar activity is over just about the entire eastern Gulf waters east of 87W and to the south of Marco over the Yucatan Channel. Isolated showers and thunderstorms are north of 24N and west of 87W. Tropical Storm Marco centered near 23.7N 87.0W 994 mb at 5 AM EDT is moving NNW at 11 kt. Maximum sustained winds 60 kt gusts 75 kt. Marco will intensify to a hurricane near 25.3N 87.6W this afternoon with maximum sustained winds 65 kt gusts to 80 kt, reach to near 27.3N 88.6W late tonight. Marco will maintain intensity as it reaches to near 29.0N 89.7W Mon afternoon and move inland and weaken to a tropical depression near 30.5N 93.1W Tue afternoon and move inland to near 31.0N 95.0W early on Wed and dissipate early on Thu. Tropical Storm Laura currently over Hispaniola will move across western Cuba Mon afternoon, then begin to gradually intensify as it moves over the southeastern Gulf of Mexico near 23.5N 84.2W late Mon night. Laura is forecast to reach near 24.9N 87.0W Tue afternoon with maximum sustained winds 60 kt gusts 75 kt, to near 26.4N 89.4W late Tue night with maximum sustained winds 75 kt gusts 90 kt and move inland near 29.9N 92.5W by late Wed night with maximum sustained winds 85 kt gusts 105 kt. Atlantic high pressure will build westward over the eastern Gulf in the wake of Laura. CARIBBEAN SEA... Please see the Special Features section above for details on Tropical Storm Laura. A rather light gradient exists across the basin away from the strong southerly winds that extend within 180 nm south of Hispaniola in association with Tropical Storm Laura. The monsoon trough axis is along 11N73W in northeastern Colombia near the border with Venezuela to 12N80W to 13N85W in Nicaragua and westward across Honduras, El Salvador, and Guatemala and into the eastern Pacific Ocean. Outside convection related to the two tropical wave described above, scattered moderate convection is increasing over the Gulf of Honduras. Isolated showers and thunderstorms are elsewhere east of 76W and south of 15N west of 15N west of 76W. Tropical Storm Marco centered near 23.7N 87.0W 994 mb at 5 AM EDT is moving NNW at 11 kt. Maximum sustained winds 60 kt gusts 75 kt. Marco will intensify to a hurricane near 25.3N 87.6W this afternoon with maximum sustained winds 65 kt gusts to 80 kt, reach to near 27.3N 88.6W late tonight. Tropical Storm Laura centered near 18.8N 70.9W 1005 mb at 5 AM EDT is moving WNW at 16 kt. Maximum sustained winds 40 kt gusts 50 kt. Laura will maintain intensity as it reaches the Windward Passage near 19.8N 73.7W this afternoon, inland eastern Cuba near 20.9N 77.5W late tonight, inland western Cuba to near 22.2N 81.1W Mon afternoon, then begin to gradually intensify as it moves over the southeastern Gulf of Mexico near 23.5N 84.2W late Mon night with maximum sustained winds 45 kt gusts 55 kt. ATLANTIC OCEAN... Please see the Special Features section above for details on Tropical Storm Laura. An upper-level cyclonic circulation center is within 850 nm to 900 nm to the east-northeast of Tropical Storm Laura. This feature has acquired more convection during the overnight hours. It is noted as a clustering of scattered moderate type convection from 21N to 25N between 54W-57W. A surface trough may be forming from this feature. Scattered showers and isolated thunderstorms are to the northwest of the upper-level cyclonic circulation from 25N to 29N and between 55W-60W. To the east of the upper-level cyclonic circulation, a 60 nm wide line of scattered showers and thunderstorms that extends from 18N48W to 24N49W marks the leading edge of an easterly surge. This feature was also hinted at by an overnight ASCAT pass. Scattered showers and thunderstorms are to the northwest of Laura south of 25N between 72W-76W, including the areas of the southeastern and central Bahamas. This activity is quickly moving westward. Relatively weak high pressure is present over the area allowing for gentle to moderate winds, with the exception of fresh to strong winds south of 26N and between 65W-67W that are due to the tighter gradient found between Laura and the broad Atlantic ridge that stretches from well northeast of the area to near 28N50W and northwestward to over the southeastern U.S. Tropical Storm Laura centered near 18.8N 70.9W 1005 mb at 5 AM EDT is moving WNW at 16 kt. Maximum sustained winds 40 kt gusts 50 kt. Laura will maintain intensity as it moves inland over Haiti to the Windward Passage near 19.8N 73.7W this afternoon, inland eastern Cuba near 20.9N 77.5W late tonight, inland western Cuba to near 22.2N 81.1W Mon afternoon, then begin to gradually intensify as it moves over the southeastern Gulf of Mexico near 23.5N 84.2W late Mon night. Otherwise, the relatively weak high pressure in place will remain through the next few days. $$ Aguirre