000 AXNT20 KNHC 102248 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Sat Sep 11 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 1800 UTC surface analysis and satellite imagery through 2230 UTC. ...SPECIAL FEATURES... Hurricane Larry is centered near 43.5N 58.2W at 10/2100 UTC or 290 nm SW of Cape Race Newfoundland moving NNE at 30 kt. Estimated minimum central pressure is 967 mb. Maximum sustained wind speed is 70 kt with gusts to 85 kt. Numerous moderate with embedded isolated strong convection extends outward for 360 nm from the center, except to 120 nm in the SW quadrant. On the forecast track, Larry will move over southeastern Newfoundland tonight. Little change in strength is expected before landfall in Newfoundland. After landfall, Larry should weaken and become an extratropical cyclone on Saturday before it merges with another low over the Labrador Sea on Sunday. Swells generated by Larry will affect Bermuda, the east coast of the United States, and Atlantic Canada through Saturday night. These swells are likely to cause life-threatening surf and rip current conditions. Please read the latest High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. A tropical wave extends along 90W from the northwest Yucatan Peninsula southward through Guatemala. This is southeast of a broad upper trough reaching from the lower Mississippi Valley to the western Bay of Campeche. The interaction of tropical wave with divergent flow aloft on the southeast side of the upper trough is supporting large clusters of showers and thunderstorms across the south-central Gulf of Mexico and northwest Caribbean Sea. The northern part of the tropical wave is forecast to move into the Bay of Campeche and merge with a pre- existing surface trough by Sunday. Environmental conditions are expected to be conducive to support gradual development thereafter, and a tropical depression is likely to form on Sunday or Monday before the system moves onshore along the western Gulf of Mexico coast. The chance of tropical depression forming over the next 48 hours is medium. Regardless of development, this disturbance is expected to produce heavy rains across portions of Central America and the Yucatan Peninsula through Saturday. Heavy rains are likely to reach portions of the western Gulf coast late this weekend. A strong tropical wave over the far eastern Atlantic along 15N, moving W at 10-15 kt. Scattered moderate convection is observed from 03N-08N between 20W-23W. A tropical depression is likely to form late this weekend or early next week as the system moves west- northwestward over the far eastern Atlantic near the Cabo Verde Islands. Interests in the Cabo Verde Islands should monitor the progress of this system. The disturbance has a medium chance of development over the next 48 hours. ...TROPICAL WAVES... An Atlantic tropical wave has an axis along 37W from 06N-22N, moving W at 15 kt. No significant convection is evident near this tropical wave. An Atlantic tropical wave has an axis along 55W from 05N-22N, moving W at 10-15 kt. No significant convection is noted with the wave at this time. A Caribbean tropical wave has an axis along 74W from 13N southward to central Colombia, moving W at 10-15 kt. No significant convection is noted with this wave at this time. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coast of Mauritania near 19N16W to 09N30W to a 1012 mb low pressure near 13N48W. Scattered moderate convection is ongoing within 120 nm north of this low pressure. GULF OF MEXICO... A stationary front reaches from near Crystal River, Florida to Brownsville, Texas. A few showers and thunderstorms are active along the front west of 90W. A sharp surface trough extends from Tabasco Mexico near 18N92.5W to just southeast of Brownsville. Scattered to numerous showers and thunderstorms are active mainly south of 25N between 82W-92W. Coastal observations confirm fresh NE to E winds off the Texas coast north of the front, with 2 to 4 ft seas. Fresh NW winds are active off Veracruz, west of the sharp surface trough, confirmed by 20 kt winds at Coatzacoalcos. Sea are also 2 to 4 ft in this area. Light breezes and slight seas are noted elsewhere. For the forecast, see the Special Features section above for information on the tropical wave that has potential to develop into a tropical cyclone over the southwest Gulf of Mexico Sunday or Monday. Elsewhere, the frontal boundary over the northern Gulf will remain nearly stationary through Sunday, bringing showers and thunderstorms across the region. CARIBBEAN SEA... Please see the Special Features section above for details on the tropical wave over Central America that is inducing convection west of 80W. A few showers and thunderstorms are active over off western Cuba in the northwest Caribbean, as well as in the far southwest Caribbean, near the monsoon trough which reaches from central Colombia to central Panama. Thunderstorms are active over the highlands of Hispaniola as well. No other significant shower or thunderstorm activity is evident. Fresh to strong trade winds and 6 to 8 ft seas are noted over the south-central Caribbean. Moderate to fresh trade winds and 4 to 6 ft seas are noted elsewhere, except for gentle to moderate SE winds and 2 to 5 ft seas over the northwest Caribbean. For the forecast, the Atlantic ridge will continue to build westward across the Caribbean, bringing an increase in the trade wind flow through the weekend. Fresh to strong winds will occur offshore Colombia and in the Gulf of Venezuela, mainly at night through Sun. Fresh to strong winds are also likely in the late evening in the Gulf of Honduras starting on Sat. Scattered showers and thunderstorms are expected to continue across the NW Caribbean today and reduce in coverage by Sat. ATLANTIC OCEAN... Please see the Special Features section above for details on Hurricane Larry over the NW Atlantic. A cold front reaches from 32N71W to near Daytona Beach, Florida. A few showers and thunderstorms are noted along this boundary west of 77W. A 1009 mb low pressure, the remnants of Tropical Depression Mindy, is near 34N70W. Fresh winds and seas to 8 ft are evident north of 28N between 67W-72W, south of this feature. The Atlantic ridge extends from 1024 mb high pressure near 34N46W through the central Bahamas, supporting light to gentle breezes and mainly 4 to 6 ft seas elsewhere west of 65W. Farther east gentle to moderate trade winds and mostly 4 to 6 ft persist south of the ridge. The exceptions are fresh winds and seas to 7 ft within 180 nm north of 1012 mb low pressure near 13N48W, and fresh to strong NE winds with 6 to 9 ft seas from 20N to the Canary Islands and east of 23N to the coast of Africa. For the forecast over the western Atlantic west of 65W, swells generated by Hurricane Larry will also subside by tonight. A frontal boundary will linger across the area through Sun which will bring showers and thunderstorms across the area during the weekend. $$ Christensen