Atlantic Discussion

  • NHC Atlantic Tropical Weather Discussion
    by (nhcwebmaster) on September 23, 2023 at 9:40 AM

    000 AXNT20 KNHC 230940 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Sat Sep 23 2023 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 0930 UTC. ...SPECIAL FEATURES... Tropical Storm Ophelia is centered near 34.3N 76.9W at 23/0900 UTC or 20 nm SW of Cape Lookout North Carolina, moving NNW at 8 kt. Estimated minimum central pressure is 981 mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt. Scattered moderate and isolated strong convection is noted within 60 nm of the center. Peak seas are currently around 28 ft. Landfall will be in the next couple of hours along the coast of North Carolina. Weakening is expected after landfall through the rest of the weekend, and winds will diminish below tropical storm force within a day or so. There is a danger of life-threatening storm surge inundation over portions of eastern North Carolina and southeastern Virginia, including Pamlico and Albemarle Sounds, the Neuse and Pamlico Rivers, the lower James River, and the lower Chesapeake Bay, where Storm Surge Warnings are in place. Residents in these areas should follow advice given by local officials. Also please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website - and the latest Ophelia NHC Forecast/Advisory and Public Advisory at for more details. Storm warning associated with Invest 90L: The axis of a tropical wave is analyzed along 36W with a 1008 mb low centered at 16N35W where the tropical intersects the monsoon trough. Maximum winds are currently 30 kt. A recent altimeter satellite pass indicated seas area approaching 12 ft in the northern quadrant of the low. Numerous moderate to isolated strong convection is noted within 90 nm of the low pressure. A tropical cyclone is likely to form during the next couple of days while the system moves generally westward at 10 kt. The system is then expected to turn west- northwestward early next week as it moves over the central tropical Atlantic. The formation chance through 48 hours is high. Please see the latest Tropical Weather Outlook at for more information. ...TROPICAL WAVES... Please see the Special Features Section for details on the tropical wave (Invest 90L) along 36W. A new tropical wave has moved off the coast of Africa, passing through 17W at 10 to 15 kt, and extending from 05N to 20N. Scattered moderate convection is noted within 30 nm either side of the tropical wave axis. A tropical wave has its axis along 61W/62W passing through near the Lesser Antilles south of 22N, moving westward around 10 kt. A few showers are noted near the wave axis. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic through the coast of Guinea-Bissau near 12N17W to 11N25W to the aforementioned low pressure (Invest 90L) near 16N35W, before terminating near 08N45W. No ITCZ is evident in the tropical Atlantic at this time. No significant convection is noted near the monsoon trough outside of the convection already described near the tropical waves. GULF OF MEXICO... Scattered showers and isolated thunderstorms continue to affect the southeast Gulf waters and the Florida Straits in association with a surface trough that extends from western Cuba to the south-central Gulf. The rest of the Gulf of Mexico is under the influence of a weak high pressure system positioned off the southern coast of Louisiana, sustaining moderate or weaker winds and seas of 1-3 ft. Stronger winds, especially in gusts, are likely occurring near the stronger convection. For the forecast, the surface trough over the southeast Gulf will drift into the western Gulf early next week and dissipate. Meanwhile, weak high pressure will persist over the north-central and northeast Gulf. This pattern will support gentle to moderate NE to E winds and slight seas across the basin through the middle of next week. CARIBBEAN SEA... A few showers and thunderstorms are active along a surface trough running parallel to the south coast of Cuba. This is at the base of an upper trough extending along the coast of Florida into the northwest Caribbean. Surface high pressure building over the western Atlantic in the wake of T.S. Ophelia is supporting moderate to fresh trade winds and 3 to 5 ft seas over the eastern and central Caribbean, except for fresh trade winds and 5 to 6 ft seas off Colombia and Venezuela. Gentle breezes and slight seas are noted elsewhere. For the forecast, the high pressure building north of the region will continue to support moderate to fresh trade winds across most of the eastern and central Caribbean through early next week, with fresh to strong pulses off northwest Venezuela and northeast Colombia during mainly the overnight and early morning hours. Looking ahead, seas will build in mixed NE and E swell across waters east of the Leeward Islands starting early Mon, ahead of low pressure moving westward across the tropical Atlantic, possibly as the next tropical cyclone. ATLANTIC OCEAN... Please see the Special Features section section above for information on Tropical Storm Ophelia and the storm warning associated with Invest 90L. Divergence aloft and low-level convergence associated with Tropical Storm Ophelia well north of the area maintain scattered moderate to isolated strong convection from the southern Bahamas to near Bermuda, and along much of the central and northern Bahamas. Farther east, scattered showers and thunderstorms are also active within 60 nm west of another deep layer trough reaching from 29N50W to 22N55W. An altimeter pass confirmed rough seas along this trough as well, due in part to large NE swell. Elsewhere outside of the vicinity of the strong winds and rough seas associated with Invest 90L, weak high pressure is maintaining gentle to moderate winds and moderate seas in mixed swell across the basin. For the forecast west of 55W, large northerly swell on the southern periphery of Ophelia will continue to impact the waters off northeast Florida through the morning. A weak ridge will build in the wake of Ophelia off Florida through early next week, and a trough will persist across the Bahamas through Mon. Looking ahead, seas will build in mixed NE and E swell across waters northeast of the Leeward Islands starting Mon, ahead of low pressure moving westward across the tropical Atlantic, possibly as the next tropical cyclone. $$ Christensen

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