000 AXNT20 KNHC 251708 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Sat Sep 25 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 1600 UTC. ...SPECIAL FEATURES... Hurricane Sam is centered near 12.9N 47.6W at 25/1500 UTC or 950 nm ESE of the Northern Leeward Islands moving WNW at 9 kt. Estimated minimum central pressure is 960 mb. Maximum sustained wind speed is 105 kt with gusts to 130 kt. Peak seas are near 23 ft and are anticipated to reach near 35 ft by Monday. A slower motion to the west-northwest is expected over the weekend, followed by a turn to the northwest on Monday. Additional strengthening is expected over the next day or so, and Sam is forecast to become a category 4 hurricane by Sunday. Numerous moderate and scattered strong convection is noted within 120 NM of Sam's center. Please read the latest High Seas Forecast issued by NHC at http://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest NHC Public Advisory and Forecast/Advisory at https://hurricanes.gov for more details. Subtropical Depression Teresa is centered near 34.3N 65.0W at 25/1500 UTC or 120 nm N of Bermuda stationary. Estimated minimum central pressure is 1009 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. A motion toward the northeast is expected to begin this afternoon and continue through Sunday morning. Teresa is expected to become a remnant low by this evening and dissipate on Sunday. Peak seas are near 13 ft and are expected to diminish below 12 ft later today. There is no significant deep convection occurring in association with Teresa currently. Please read the latest High Seas Forecast issued by OPC at https://ocean.weather.gov/mobile/mobile_product.php?id=NFDHSFAT1 and the latest NHC Public Advisory and Forecast/Advisory at https://hurricanes.gov for more details. ...TROPICAL WAVES... An Atlantic tropical wave has its axis near 31W, south of 17N, and it is moving west around 10 kt. Isolated moderate convection is noted from 04N-10N between 24W-36W. Satellite imagery show that the northern part of the wave remains embedded in dry Saharan air, inhibiting the development of shower and thunderstorm activity. A Caribbean tropical wave has its axis near 65W, south of 20N, and it is moving west around 10-15 kt. No significant deep convection is noted in association with this wave. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through coast of Senegal near 12N17W to 06N37W. The ITCZ extends from 08N40W to 07N59W to the coast of Guyana. Aside from convection associated to the tropical waves and Sam described above, scattered moderate and isolated strong convection is noted from 10N-15N east of 23W. GULF OF MEXICO... As of 1500 UTC, a stationary front extends from the NE Gulf to the Bay of Campeche. Scattered moderate convection is noted from 23N-27N between 85W-93W. West of the front are moderate or weaker N to NE winds. East of the front, winds are gentle or weaker. Seas are 3-4 ft west of the front, and 1-2 ft east. For the forecast, the front will push southward on Sun and dissipate by early next week. Moderate to locally fresh winds prevail north of the front. Winds and seas will diminish across basin through early next week as high pressure builds over the northern Gulf. CARIBBEAN SEA... Refer to the section above for details on the tropical wave moving across the easter Caribbean. A modest north-south pressure gradient exists over the Caribbean today between the 1009 mb Colombian Low and weak ridging north of the Caribbean. This is forcing fresh E trades over the S central Caribbean and moderate or weaker trades elsewhere. Seas are 5-6 ft over the S central Caribbean and 2-4 ft elsewhere. Scattered moderate and isolated strong convection is noted from 10N-15N west of 80W. For the forecast, Hurricane Sam near 12.9N 47.6W 960 mb at 11 AM EDT moving WNW at 9 kt. Maximum sustained winds 105 kt gusts 130 kt. Sam will move to 13.3N 48.7W this evening, 13.7N 49.8W Sun morning, 14.3N 50.8W Sun evening, 15.0N 51.9W Mon morning, 15.8N 53.0W Mon evening, and 16.6N 54.1W Tue morning. Additional strengthening is expected over the next day or so. Meanwhile, moderate trade winds will persist over much of the Caribbean into early next week, while fresh winds prevail over the south- central Caribbean as high pressure builds east of the Bahamas. ATLANTIC OCEAN... Please read the sections above for details on Hurricane Sam and tropical waves moving across the basin. The Cumbre Vieja volcano on the island of La Palma in the Canary Islands has been erupting since 19/1410 UTC. Significant volcanic ash mainly 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 issued no later than 25/2100 UTC. A stationary front extends from 31N75W to 27N80W at the Florida peninsula. A pre-frontal trough extends from 27N76W to 26N80W. Isolated moderate convection is noted from 24N-30N between 73W- 80W. A surface trough extends from 27N63W to 23N68W. Scattered moderate and isolated strong convection is noted from 24N-30N between 58W-64W. Farther east, a dissipating cold front is noted from 31N34W to 27N42W to 28N50W, where it transitions to a dissipating stationary front to 31N54W. A 1010 mb low - the remnants of Rose - is located just southeast of the cold front at 28N34W. Scattered moderate convection is noted north of 25N between 29W-34W. S winds just east of the low are fresh to strong. Elsewhere across tropical N Atlantic (aside from near Hurricane Sam), the winds are moderate or weaker. For the forecast west of 65W, the stationary front will remain stationary through early Sun, pushing south and eastward as a weak cold front by Sun and reach from 31N69W to 24N80W by Mon morning. The front will stall and dissipate by Wed. Farther east, Hurricane Sam near 12.9N 47.6W 960 mb at 11 AM EDT moving WNW at 9 kt. Maximum sustained winds 105 kt gusts 130 kt. Sam will move to 13.3N 48.7W this evening, 13.7N 49.8W Sun morning, 14.3N 50.8W Sun evening, 15.0N 51.9W Mon morning, 15.8N 53.0W Mon evening, and 16.6N 54.1W Tue morning. Additional strengthening is expected over the next day or so, and will reach near 18.4N 56.5W by early Wed. $$ Landsea/A.Reinhart