000 AXNT20 KNHC 231102 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Thu Sep 23 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 0600 UTC surface analysis and satellite imagery through 1030 UTC. ...SPECIAL FEATURES... Tropical Depression Eighteen is centered near 10.5N 36.4W at 23/0900 UTC or 1620 nm ESE of the Northern Leeward Islands moving W at 13 kt. Estimated minimum central pressure is 1008 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Convection is becoming better organized within 120 nm in the northwest semicircle of the center of the depression. Seas are estimate to be reaching 10 ft currently, but will build throughout today within 120 nm on the north side of the low as it continues to move westward. The depression is expected continue to intensify and reach tropical storm strength later today, and likely become a hurricane Sat. Please read the latest the latest NHC Forecast/Advisory and Public Advisory for T.S. Eighteen at www.hurricanes.gov for more details. Recently downgraded Post-Tropical Cyclone Rose is centered near 25.2N 41.6W at 23/0900 UTC or 1130 nm WNW of the Cabo Verde Islands moving NW at 9 kt. Estimated minimum central pressure is 1010 mb. The center remains fully exposed with no significant convection noted in its vicinity. An earlier CryoSat-2 altimeter pass indicated seas were still reaching near 12 ft within 120 nm in the northeast quadrant of Rose. This is not really due to the winds near Rose, and is actually due to a larger area of northerly swell causing 8 to 12 ft seas north of 22N between 35W and 60W. Rose will move more north tonight, then northeast through Fri, before gradually dissipating through Sat. Please read the latest the latest Rose NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. A gale-force, non-tropical low pressure system, the remnants of Odette, is located about 600 miles west-northwest of the westernmost Azores. Showers and thunderstorms have increased a little near the low, and there is a medium chance it could become a subtropical or tropical cyclone while it moves generally southward over marginally warmer waters during the next couple of days. Strong upper-level winds are expected to develop over the system this weekend, which should limit its development. Additional information on this system, including gale warnings, can be found in High Seas Forecasts issued by the Ocean Prediction Center ocean.weather.gov. Also see the latest Tropical Weather Outlook at www.hurricanes.gov for more details. ...TROPICAL WAVES... A tropical wave is evident just east of the Cabo Verde Islands along 21W from 05N to 20N. Scattered moderate convection is noted from 03N to 07N east of 22W. Another tropical wave is analyzed along 50W/51W south of 20N. No significant convection is noted near the wave axis. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the the Senegalese coast near 15N17W to 08N25W to 08N30W. A segment of the ITCZ extends from 07N40W to 06N48W, and from 06N51W to 06N57W. Other than the convection noted in the Tropical Wave section, no significant convection is observed along the monsoon trough or in association with the ITCZ. GULF OF MEXICO... An early season cold front is moving across the northern Gulf, and currently extends from Crystal River, Florida to Poza Rica, Mexico. Scatterometer satellite data along with recent buoy observations indicate fresh to strong northerly winds are following the front. This includes and area of fresh to strong NW winds just of the Mexican coast near Tampico. Altimeter satellite data along with recent buoy observations are showing seas building to 6 to 8 ft behind the front. Light to gentle breezes and slight seas are noted south of the front. Scattered moderate convection is noted mainly along the coast of Mexico, south of 24N and west of 95W, as well as a few thunderstorms along the front between 85W and 90W. For the forecast, the front will continue to move southeastward through tonight, stall from roughly Fort Myers, Florida to the coast of Veracruz, Mexico near 18N95W Fri, then dissipate Sat. Fresh to strong winds will follow the front into tonight, including along the coast of Veracruz where seas may build to 8 ft. Looking ahead, winds and seas will diminish across basin from Sat and into early next week as high pressure builds over the northern Gulf. CARIBBEAN SEA... A sharp upper trough across eastern Cuba continues to support scattered overnight showers and thunderstorms from the southern peninsula of Haiti to Jamaica. Scattered showers and thunderstorms are also evident north of the monsoon trough off the coast of Colombia and eastern Panama. A weakened subtropical ridge north of the area continues to support a pattern of below average winds across the basin. Moderate trade winds are noted over the southeast Caribbean, with generally light to gentle trade winds elsewhere. Seas are 1 to 3 ft over the northwest Caribbean, and 3 to 5 ft elsewhere. For the forecast, Tropical Depression Eighteen is well to the east near 10.5N 36.4W 1008 mb at 0900 UTC, moving W at 13 kt. Maximum sustained winds are 30 kt with gusts 40 kt. Eighteen will will continue to intensify as it moves across the Atlantic, becoming a hurricane near 13N47W by Sat afternoon, and reaching 55W east of the Leeward Islands by Mon. Marine interests in the Leeward Islands should stay aware of the expected track of this developing system. Meanwhile, moderate trade winds will persist over much of the Caribbean into early next week, becoming fresh over the south- central Caribbean starting Fri night as high pressure builds east of the Bahamas. ATLANTIC OCEAN... Please read the Special Features section above for details on the Tropical Depressions Rose and Eighteen. The Cumbre Vieja volcano on the island of La Palma in the Canary Islands has been erupting since 19/1410 UTC. The volcano is still emitting ashes, mainly around the volcano drifting SSW below 10,000 ft, and NE above 10,000 ft. Marine and aviation interests should monitor this on-going situation by reading Volcanic Ash Advisory issued by Meteo-France at http://vaac.meteo.fr/volcanoes /la-palma/. The next advisory will be issue no later than 23/0900 UTC. A stationary front extends from 32N42W to 27N60W to 31N78W to low pressure off the coast of South Carolina. An associated cold front is moving off the Georgia and northeast Florida coasts, reaching from the low pressure to near Jacksonville, Florida. Scattered showers and a few thunderstorms are ongoing within 120 nm north of the stationary front between 60W and 65W. To the south of the stationary front, the 1008 mb remnant low of Peter persists near 22N67W. A large area of moderate to strong convection is flaring from the center of the partially exposed low, to within 90 nm of the center. A recent altimeter pass over this low showed seas are at least seven feet, maybe eight, within 180 nm to the north of the center. This is due in part to northerly swell that recently entered the area. Aside from the features and related winds and seas already mentioned in this discussion, moderate to occasionally fresh trade winds are noted across the basing, with 4 to 6 ft seas in open waters. For the forecast west of 65W, the remnant low of Peter will dissipate as it drifts northeast of the region through Fri. Meanwhile, the cold front moving off the northeast Florida coast this morning will stall from 31N77W to near Fort Pierce, Florida by tonight, then dissipate through early Sun just before a second weak front possibly moves into the region early next week. Farther east, Tropical Depression Eighteen will continue to intensify as it moves across the Atlantic, becoming a hurricane near 13N47W by Sat, and reaching 55W east of the Leeward Islands by Mon. $$ Christensen