000 AXNT20 KNHC 261748 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Thu Aug 26 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 Depression Nine formed this morning in the western Caribbean Sea. As of 1800 UTC, T.D. Nine was centered near 17.5N 79.5W, or about 85 nm SW of Negril, Jamaica, moving NW at 11 kt. Maximum sustained winds are near 30 kt with gusts to 40 kt. Minimum central pressure is 1005 mb. Peak seas are 10 ft. Numerous moderate and scattered strong convection is within 330 nm of the center in the NE semicircle, including over Jamaica, southeastern Cuba and the western part of the peninsula in SW Haiti. Scattered moderate convection is within 300 nm SE to S of the center. On the forecast track, the depression will pass near or over the Cayman Islands tonight, the Isle of Youth and western Cuba Friday, and move over the southeastern and central Gulf of Mexico Friday night and Saturday. The system is forecast to approach the U.S. northern Gulf coast on Sunday. Steady strengthening is forecast during the next few days. The depression is expected to become a tropical storm tonight, and become a hurricane when it is near western Cuba or over the southeastern Gulf of Mexico. Additional strengthening is likely over the Gulf of Mexico and the system could be near major hurricane strength when it approaches the northern Gulf coast. Tropical storm conditions are expected in the Cayman Islands tonight, and are expected to reach the Isle of Youth and portions of western Cuba on Friday. Heavy rainfall is expected to produce significant flooding across the Cayman Islands, western Cuba, the Isle of Youth and the northeastern Yucatan Peninsula. Please see 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 for more details. Please refer to the NHC High Seas Forecasts at https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for marine impacts. A trough of low pressure located over the central Atlantic extends from 25N61W to 1014 mb low pressure near 31N55W to 37N51W. Scattered moderate and isolated strong convection is noted from 26.5N-33N between 51W-60W. Environmental conditions are forecast to be generally conducive for development, and a tropical depression is likely to form this weekend. The system is expected to move slowly eastward during the next day or two, but a faster northeastward motion is forecast to begin on Sunday. Please refer to the latest Tropical Weather Outlook at www.hurricanes.gov for more details. A tropical wave located along 40/41W over the central tropical Atlantic is producing disorganized numerous moderate and scattered strong convection from 10N-15N between 39W-44W. Environmental conditions are expected to be conducive for development during the next few days, and a tropical depression is likely to form over the weekend while the system moves toward the west-northwest or northwest at 10 to 15 kt. The disturbance is forecast to turn northward early next week. The chance of tropical cyclone formation within 48 hours is medium. Please refer to the latest Tropical Weather Outlook at www.hurricanes.gov for more details. ...TROPICAL WAVES... A tropical wave is along 21W S of 18N, moving W at 10 kt. Isolated showers are seen near where the wave intersects the monsoon trough. Please see the Special Features section above for details on the tropical wave along 40/41W. The axis of a tropical wave is along 59W from 07N-19N, moving W at 10 to 15 kt. Isolated showers are seen south of 10N near the wave axis. The axis of a tropical wave is along 80W S of 16N, moving W at 10 kt. Numerous moderate and scattered strong convection is seen near where the wave intersects the east Pacific monsoon trough, from 09N-12N between 79W and the coasts of western Panama, Costa Rica and SE Nicaragua. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic Ocean near the border of Senegal and Guinea-Bissau near 12N17W to 14N34W to 12N41W to 08N46W to 07N52W. The ITCZ continues from 07N52W to 09N58W. Aside from convection noted in the sections above, scattered moderate isolated strong convection is observed from 10N-12N between 14W- 19W and from 06.5N-09N between 42W-56W. GULF OF MEXICO... A surface trough over the northwest Gulf of Mexico is producing numerous moderate and isolated strong convection from 27N-29.5N between 91W-96.5W. Another surface trough is located over the eastern Gulf of Mexico extending from Tampa Bay to the western tip of Cuba. Scattered moderate convection is noted from 23N-28N between 82.5W-85W. A recent ASCAT pass shows fresh winds on both sides of the trough axis over the eastern Gulf of Mexico and the Yucatan Channel. Gentle winds and mainly fair weather prevail over the southwest Gulf, except for isolated tstorms noted near the coast of Veracruz. Seas are currently 1 to 3 ft over the western Gulf. Seas are 4-6 ft in the Florida Straits, Yucatan Channel and southeast Gulf, due to the aforementioned surface trough and fresh winds. For the forecast, Tropical Depression Nine will strengthen to a tropical storm in the northwest Caribbean Sea near 18N80W this evening, cross western Cuba Fri evening, strengthen to a hurricane over the Gulf of Mexico near 24N86W Sat morning, be near 28N90W Sun morning as a strong hurricane, and move inland over Louisiana Mon morning. For more details on Tropical Depression Nine, see the special features section above. CARIBBEAN SEA... Please see the special features section above for details on Tropical Depression Nine, currently located 85 nm SW of Negril, Jamaica. Please see the tropical waves section above for details on the tropical wave along 80W. The eastern Caribbean east of 70W is free of any significant precipitation areas. Moderate to fresh trade winds prevail over the area, with 4 to 6 ft seas. Farther west, the latest ASCAT pass shows strong E to SE winds just south of Haiti. In the northwest Caribbean, conditions are quiet west of 83W for the moment, except for the Yucatan Channel and just east of the Yucatan Peninsula, where fresh NE winds and seas of 4 to 6 ft are noted. Scattered moderate showers are seen within 60 nm of the Yucatan coast from the Belize border to Cozumel. For the forecast, Tropical Depression Nine will strengthen to a tropical storm in the northwest Caribbean Sea near 18N80W this evening, move near or over western Cuba near 22.5N 84W Fri evening, then strengthen to a hurricane over the Gulf of Mexico near 24N86W Sat morning. Tropical storm force winds and seas over 12 ft will exit the northwest Caribbean by Sat morning. Moderate to fresh winds are expected elsewhere through the forecast period, except for locally strong winds in the south-central Caribbean. ATLANTIC OCEAN... Please see the special features section above for details on a trough of low pressure over the central Atlantic near 31N55W, which has the potential for tropical cyclone development. An upper-level trough over Florida and the eastern Gulf of Mexico is inducing upper-level diffluence to the east of northern Florida. Numerous moderate and isolated strong convection is noted east of northern Florida from 27.5N-31N between 74W-81W. A recent ASCAT pass shows fresh east winds occurring in the same area. Seas are 5 to 7 ft in this area. Farther south, scattered showers extend off the north coast of eastern Cuba south of 23N between 74W-80W, associated with the outermost rain bands of T.D. Nine. Fresh trade winds prevail from the Bahamas to Cuba and westward through the Florida Straits. Gentle to moderate wind speeds prevail farther east from 20N-26N between 50W-70W, where seas are 4 to 5 ft. In the northeast portion of the area, a cold front extends from 31N26W to a 1014 mb low pressure near 29N29W. A surface trough extends from the low SW to 23N35W. Fresh NE winds and 6 to 8 ft seas are west of the low and surface trough. A recent ASCAT pass shows fresh to strong trades in the area from 12N-20N between 37W-51W, where seas are 7 to 10 ft. For the forecast west of 65W, high pressure located just N of the forecast region near 34N70W will dominate the western Atlantic through Mon, supporting mainly moderate E to SE winds. Fresh to locally strong winds are expected to pulse N of Hispaniola during the evening hours through Sat night. $$ Hagen