000 AXNT20 KNHC 042201 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Tue Oct 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 2030 UTC. ...SPECIAL FEATURES... Hurricane Sam is centered near 45.1N 42.5W at 04/2100 UTC or 450 nm E of Cape Race, Newfoundland, moving NE at 31 kt. Estimated minimum central pressure is 965 mb. Maximum sustained wind speed is 80 kt with gusts to 100 kt. Peak seas are near 48 ft and seas of 12 ft or greater extend out up to 690 nm mainly SW of the center. Numerous moderate to isolated strong convection is noted up to 90 nm from the center, with scattered moderate convection noted within 180 nm of the center, mainly in the NW quadrant. The quick northeast forward speed is expected to continue overnight with a slowly likely to commence Tue as Sam begins to merge with an non-tropical low pressure system. Gradual weakening is expected tonight but an approaching mid-latitude trough should result in a rapid transition into a powerful extratropical cyclone by Tue. Hurricane-force winds will likely continue after this transition, into Tue night. Large swell continues to be generated by Sam spreading in all directions, with the S edge of this swell reaching as far S as 28N. Please read the latest High Seas Forecast issued by the Ocean Prediction Center at the website https://ocean.weather.gov/mobile/mobile_product.php?id=NFDHSFAT1 and the latest NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. A strengthening 1027 mb Azores high is generating near-gale NNE to NE winds near the Canary Islands. For more information, please read the METEO-FRANCE high seas forecast at the following website, http://weather.gmdss.org/II.html ...TROPICAL WAVES... An Atlantic tropical wave is along 32W from 19N southward, moving W at around 15 kt. Scattered moderate to isolated strong convection is seen from 04N to 10N between 28W and 38W. A Caribbean tropical wave is near 76W from 17N southward into N Colombia, and moving W at 10 to 15 kt. Aided by divergent flow aloft, scattered moderate convection is occurring over the central and N central Caribbean Sea, including Jamaica and S Hispaniola. ...MONSOON TROUGH/ITCZ... A modest monsoon trough passes through the coast of Mauritania near 18N16W to just E of the Cabo Verde Islands at 17N21W. The ITCZ extends from 07N21W to 06N30W and from 05N33W to 04N42W. Scattered moderate convection is noted within 150 nm on both sides of the ITCZ axis. The eastern end of the E Pacific monsoon trough that extends along 10N from Costa Rica to Colombia in the SW Caribbean is triggered numerous moderate to isolated strong convection in the area, including the Nicaragua coast. ...GULF OF MEXICO... A weak cold front has stalled this afternoon in the NW Gulf, from the central Louisiana coast to just S of the Texas-Mexico border. This feature is producing scattered showers and isolated thunderstorms over the N central and NW Gulf. Convection over and near the Florida Panhandle is being enhanced by a surface trough that has formed ahead of the stationary front, from Mobile Bay southward to around 28N. A trough previously over the central Bay of Campeche has dissipated, and associated convection has diminished this afternoon. Weak surface ridging dominating the basin is leading to mainly light to gentle winds and seas of 1 to 3 ft. Some moderate NE winds are occurring offshore the western Yucatan Peninsula, and locally moderate NE winds are also present behind the stalled frontal boundary offshore the lower Texas coast. For the forecast, a weak ridge north of the Gulf along 30N will move eastward through Wed, supporting tranquil conditions across all but the southeast sections of the basin, where moderate trades will prevail. A front will remain nearly stationary over the NW Gulf into mid-week. ...CARIBBEAN SEA... Convergent trades are producing scattered showers and a few thunderstorms along the coast of Belize and Honduras, and adjacent waters. Refer to the Tropical Waves and Monsoon Trough/ITCZ sections for additional convection in the basin. Tightening gradient between the Bermuda high and E Pacific monsoon trough is generating strong trade winds with seas of 7 to 10 ft across the central basin. Fresh trades and seas at 6 to 8 ft are evident over the E basin. Gentle to moderate trades and seas of 3 to 5 ft prevail for the rest of the basin. For the forecast, high pressure off of the mid Atlantic coast will gradually slide towards the east through the middle of the week. This pattern will produce fresh to strong trade winds across the NE and central Caribbean through Tue night. Fresh to strong trade winds will then persist across the central Caribbean through Thu. Moderate N to NE swell will affect the tropical Atlc waters through Wed. ...ATLANTIC OCEAN... See Special Features Section above for details on Hurricane Sam and near-gale conditions in the eastern Atlantic near the Canary Islands. The remnants of Tropical Depression Victor have opened into a trough that stretches from 24N45W to 15N45W. Fresh east winds and seas of 8 to 10 ft are within about within about 90 nm of this trough on both sides of the axis. A cluster of moderate convection is noted in association with this trough, from 20N to 23N between 41W and 47W. This trough will gradually weaken as it moves WNW over the next couple of days. A deep layer trough from the SE Bahamas northward to SE and offshore of the North Carolina coast is producing a large area of scattered showers and thunderstorms from Hispaniola to 30N, between 65W and 72W. Upper-level winds are not expected to be favorable for significant development of this system will it moves slowly NW over the next several days. Aside from the convection associated with the aforementioned troughs, showers and thunderstorms are associated with the tropical wave and ITCZ and is described in the respective sections above. The Cumbre Vieja volcano, that is on the island of La Palma in the Canary Islands, has been erupting since 19 September at 1410 UTC. An ash cloud reaching 10,000 ft or 3000 m is drifting southward from the volcano. Marine and aviation interests should monitor this on-going situation by reading the Volcanic Ash Advisory, that is issued by Meteo-France at http://vaac.meteo.fr/volcanoes/la-palma/ S of 25N, generally moderate to fresh trades prevail, with light to gentle winds to the north. Locally strong NE winds are occurring near the coast of NW Africa due to a tight pressure gradient, otherwise the highest winds are fresh to locally strong in the vicinity of the Leeward Islands. Seas are 6 to 8 ft, although an area of 8 to 10 ft seas is located N of 25N between 40W and 60W. For the forecast W of 50W, high pressure along the mid Atlc coast will slide slowly eastward through mid week. This will produce moderate to fresh trade winds south of 23N and east of the Bahamas through Tue before spreading into the southeast Bahamas Wed night. The swell generated from Hurricane Sam will continue to impact the SW N Atlantic including the Bahamas through Wed. An active weather pattern is expected across the waters E of 75W and NE the Bahamas tonight through Tue as a surface trough becomes better defined across the SE Bahamas and shifts slowly NW. $$ KONARIK