000 AXNT20 KNHC 232312 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Fri Sep 24 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 2250 UTC. ...SPECIAL FEATURES... Tropical Storm Sam is centered near 11.1N 39.7W at 2100 UTC or 1420 nm ESE of the Northern Leeward Islands moving W at 14 kt. Estimated minimum central pressure is 1000 mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt. Satellite imagery depicts a system that is becoming better organized. Numerous moderate to strong convection is noted within about 50 nm of the center. Scattered moderate to strong convection is elsewhere in bands within 240 nm N and 120 nm S semicircles. Peak seas are up to 15 ft within 90 nm of the center in the NE quadrant and within 60 nm of the center in the NW quadrant. Sam is forecast to move WNW for the next couple of days and intensify, becoming a hurricane on Fri and be near major hurricane intensity by the end of the weekend. Please, read the 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 Peter 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 near 44N42W, or a little more than 550 nm west-northwest of the westernmost Azores. While showers and thunderstorms remain limited near the low, only a small increase in this activity could result in the formation of a subtropical or tropical cyclone while it moves generally southeastward over marginally warmer waters during the next day or so. Strong upper- level winds are expected to develop over the system beginning tomorrow, which should then limit further 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 far eastern Atlantic tropical wave has its axis just east of the Cabo Verde Islands near 23W from 05N to 20N, moving westward at 10 kt. Scattered moderate isolated strong convection is seen from 05N to 12N between 16W and 27W. A central Atlantic tropical wave has its axis along 54W from 05N to 21N, moving westward at 10-15 kt. Scattered moderate convection is noted from 11N to 15N between 54W and 57W. ...MONSOON TROUGH/ITCZ... The monsoon trough axis passes through the the Senegalese coast near 15N17W to 08N22W to 08N30W. A segment of the ITCZ extends from 08N40W to 06N47W. Aside from convection associated to the tropical waves and Sam described above, scattered moderate isolated strong convection is from 03N to 07.5N between 26N and 33W. GULF OF MEXICO... An early season cold front is moving slowly across the Gulf, extending from near Sarasota, Florida to Veracruz, Mexico. Late morning ASCAT data passes along with current buoy observations indicate fresh to locally strong north to northeast winds behind the front. Moderate to fresh northwest winds are are along and just offshore the coast of Mexico from Veracruz to Tampico. Recent altimeter satellite data along with current buoy observations are showing seas in the range of 4-7 ft behind the front, except to 9 ft offshore of Veracruz. Generally, light to gentle breezes and slight seas are noted south of the front. Scattered moderate isolated strong convection is along and within about 90 nm north of the front, west of 83W. A drier and stable air mass under high pressure is following in behind the front. The cold front will stall tonight, then dissipate Sat. Fresh to strong winds will follow the front into tonight, including along the coast of Veracruz where seas will be around 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-level trough extends from the vicinity of the southeastern Bahamas to across eastern Cuba and to the southwestern Caribbean. This trough is acting on an already very moist and unstable environment resulting in enhanced scattered moderate to strong convection over the far south- central and southwestern Caribbean from along the coast of Colombia and Panama to 15N and between 73W-81W. 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 relatively low, in the 2-3 ft range, except for slightly higher seas of 3-4 ft across the waters north of the A-B-C Islands. For the forecast, Tropical Storm Sam near 10.9N 38.1W 1003 mb at 1500 UTC, moving W at 14 kt. Maximum sustained winds are 45 kt with gusts to 55 kt. Sam will continue to intensify as it moves across the Atlantic, becoming a hurricane near 12N45W by Fri evening, and reaching 55W east of the Leeward Islands by Mon night. 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 newly formed Tropical Storm Sam. The Cumbre Vieja volcano on the island of La Palma in the Canary Islands has been erupting since 19/1410 UTC. A significant ash emission is ongoing in the vicinity of the volcano. 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 23/2300 UTC. A stationary front extends from near 31N45W to 27N68W. Morning ASCAT data depicted moderate to mainly fresh east to southeast winds north of the stationary front between 56W-59W. A cold front has moved off the southeastern United States coast and extends from 31N78W to inland central Florida. A pre-frontal trough extends just SE of the front to inland South Florida. Satellite imagery shows scattered showers and thunderstorms north of 26N and between 73W-79W. Broken to overcast multilayered clouds with embedded areas of rain along with scattered and isolated thunderstorms are seen north of 25N between 57W-64W. The 1009 mb remnant low of Peter is near 24N67W. A trough extends northeast from the low to 26N64W, and southwest from the low to the north- central coast of Hispaniola. An expanding area of scattered moderate to isolated strong convection is well removed to the east of the low from 22N to the stationary front and between 60W- 65W. Similar activity is also from 19N to 22N between 63W-67W. Morning ASCAT data showed fresh to strong southerly winds with this convective activity. Altimeter data indicates seas up to 7 ft northeast and east of the low from 22N to 28N between 62W-67W. Seas may be slighter higher in the strong convection. The post-tropical cyclone remnant 1010 mb low of former tropical cyclone Rose is near 27N42W. A trough to its southwest extends from 23N45W to 19N48W. Morning altimeter pass has seas up to 11 ft within about 60 nm in the northwest quadrant of this low. This attributed to a large area of northerly swell that is producing seas of 8-12 ft seas north of 22N between 35W-60W. Fresh east to southeast winds are over the eastern semicircle of the low. The low will gradually dissipate through Sat. Aside from the features and related winds and seas already mentioned in this discussion, moderate to occasionally fresh trade winds are noted across the basin along with 4 to 6 ft seas in open waters. For the forecast west of 65W, a cold front extending from 31N78W to Cape Canaveral, Florida 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 late Sun. Farther east, Tropical Storm Sam will intensify to a hurricane by Fri afternoon near 12N44W and to a major hurricane Sat afternoon near 13N47W. Sam will reach near 15N 52.5W Mon and be near 17.5N 55.5W Tue. $$ Stripling