000 AXNT20 KNHC 252300 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Sun Sep 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 1800 UTC surface analysis and satellite imagery through 2200 UTC. ...SPECIAL FEATURES... Hurricane Sam is centered near 13.3N 48.5W at 2100 UTC, or 890 nm ESE of the Northern Leeward Islands, moving WNW at 9 kt. Estimated minimum central pressure is 943 mb. Maximum sustained wind speed is 120 kt with gusts to 145 kt, making Sam a category 4 hurricane on the Saffir-Simpson scale. Peak seas are estimated near 29 ft and are anticipated to reach near 34 ft by Monday. Satellite imagery shows numerous moderate to strong convection within 90 nm of Sam's center, with a well define eye 12-15 nm wide. A slower motion to the west-northwest is expected during the next couple of days before Sam begins to turn more northwest and increase its forward speed. Additional strengthening is expected to continue during the next 6-12 hours, then minor fluctuations in intensity are likely as Sam goes through eye wall replacement cycles over warm waters and light wind shear. 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. Post-Tropical Cyclone Teresa is centered near 34.4N 64.3W at 2100 UTC, or about 130 nm N of Bermuda, drifting east at 4 kt. Estimated minimum central pressure is 1010 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Teresa remains a swirl of low-level clouds and lacks any convection near the center, and has thus lost all tropical or subtropical characteristic. A motion toward the northeast is expected to continue through Sunday morning before dissipating later on Sun. 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 been added to the 1800 UTC surface analysis along 21W, south of 17N, and it is moving west around 10 kt. Scattered moderate isolated strong convection is seen from 03.5N to 15N between 18W and 26W. Dry Saharan air can be seen moving off Africa with this wave from 14N to 24N extending from the coast to 26W. An Atlantic tropical wave has its axis near 32W, south of 17N, and it is moving west around 10 kt. Widely scattered moderate convection is noted from 04N-12N between 26W-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 to the north of 11N. A Caribbean tropical wave has its axis near 67W, south of 20N, and it is moving west around 15 kt. No significant deep convection is noted over water in association with this wave. However scattered moderate to strong convection is seen along the wave axis over coastal Venezuela. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through coast of Senegal near 13.5N17W to 07N33W. The ITCZ extends from 07N33W to 08N43W. Aside from convection associated to the tropical waves and Sam described above, scattered moderate isolated strong convection is noted from 04N-09N from 36W to 48W. GULF OF MEXICO... A stationary front extends from the NE Gulf to the central Bay of Campeche. Widely scattered moderate convection is noted within 60 nm either side of the front west of 83.5W. West of the front are moderate or weaker N to NE winds. East of the front, E to SE winds are gentle or weaker. Seas are 3-5 ft west of the front, and 1-2 ft east. 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 very modest north-south pressure gradient exists over the Caribbean this afternoon between a broad 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 4-6 ft over the S central Caribbean and 2-4 ft elsewhere. Scattered moderate to strong convection is noted from 10N-17N west of 80W. Hurricane Sam will move to 13.7N 49.4W Sun morning, 14.3N 50.5W Sun afternoon, 14.9N 51.6W Mon morning, 15.7N 52.7W Mon afternoon, 16.6N 53.9W Tue morning, and 17.4N 55.0W Tue afternoon. Sam will change little in intensity as it moves near 19.5N 58.0W Wed afternoon. Meanwhile, moderate trade winds will persist over much of the Caribbean into early next week. Fresh winds will prevail over the south-central Caribbean as high pressure builds east of the Bahamas through Mon. Swell fro Sam will reach the Lesser Antilles Tue morning. 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 along the Florida coast. A pre-frontal trough extends from 27N76W to 26N80W. Widely scattered moderate convection is noted within 90 nm SE of the front. Moderate N to NE winds prevail west of the front. To the east a 1016 mb high is centered near 29N68W. To the east of this, a trough, the remnants of Peter, extends from 28N63W to 22N68W. Fresh S to SW winds prevail within 180 nm east of the trough. Scattered moderate to strong convection continues east of the trough from 24N to 29N eastward to 58W. Farther east, a dissipating frontal trough is noted from 31N33W to 26N40W to 31N54W. A 1009 mb low - the remnants of Rose - is located along the trough at 28.5N34W. Scattered moderate isolated strong 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. The stationary front across the NW waters will linger through tonight, then push southeast as a weak cold front by Sun and reach from 31N68W to 23N81W by Mon morning. The front will then stall and dissipate by Tue. Farther east, Hurricane Sam will move to 13.7N 49.4W Sun morning, 14.3N 50.5W Sun afternoon, 14.9N 51.6W Mon morning, 15.7N 52.7W Mon afternoon, 16.6N 53.9W Tue morning, and 17.4N 55.0W Tue afternoon. Sam will change little in intensity as it moves near 19.5N 58.0W Wed afternoon. Swell associated with Sam will reach the Atlantic waters north of Puerto Rico and the Virgin Islands Wed and the Bahamas and waters E of 75W on Thu. $$ Stripling