000 AXNT20 KNHC 241709 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Tue Oct 24 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 1200 UTC surface analysis and satellite imagery through 1745 UTC. ...SPECIAL FEATURES... Hurricane Tammy is centered near 24.2N 62.3W at 24/1500 UTC or 500 nm SSE of Bermuda, moving NE at 7 kt. Estimated minimum central pressure is 987 mb. Maximum sustained wind speed is 65 kt with gusts to 80 kt. Peak seas near the center are estimated at 27 ft. Numerous moderate to strong convection is seen within 120 nm NE quadrant of the center. Similar convective activity is also noted in an outer band from 21N to 25N between 59W and 61W. Tammy is moving toward the northeast, and this general motion is expected to continue through Wednesday. A turn toward the north at a slower forward speed is forecast to begin on Thursday, followed by a bend to the northwest on Friday. Slight strengthening is possible during the next day or so followed by steady weakening. Tammy is forecast to become a post- tropical cyclone on Thursday. Swells generated by Tammy will continue to affect portions of the Leeward Islands, the British and U.S. Virgin Islands, and Puerto Rico during the next few days. These swells are likely to cause life-threatening surf and rip current conditions. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at the website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest Tammy NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. Tropical Depression Twenty-One has dissipated inland over Nicaragua, and the National Hurricane Center issued the last advisory on this system at 24/1500 UTC. At this time, the remnants of Twenty- One are centered near 13.6N 84.8W or 110 nm NNW of Bluefields Nicaragua, moving WNW at 3 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 20 kt with gusts to 25 kt. Clusters of numerous moderate to strong convection are occurring from 10N to 13N between 80W and 85W. The remnants are moving toward the west-northwest and a gradual turn toward the west is expected soon. The remnants of the tropical depression are expected to produce additional rainfall totals of 4 to 8 inches with maximum amounts of 12 inches across Nicaragua and 2 to 4 inches with maximum amounts of 6 inches across southern and eastern Honduras. These rains are likely to produce flash and urban flooding, along with mudslides in areas of higher terrain. Please read the latest NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. Western Atlantic Very Rough Seas: The tightening pressure gradient between high pressure of 1030 mb over the east coast of United States and Hurricane Tammy will support a large area of of strong to near-gale force NE winds and very rough seas of 12 to 17 ft across much of the area from 21N to 31N, between the east coast of Florida and 60W, starting this afternoon and continuing through Friday. Mariners should either seek to avoid this region, or use extreme caution in this area, depending on your vessel type and cargo. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at the website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details. ...MONSOON TROUGH/ITCZ... A monsoon trough enters the Atlantic through the coast of Guinea near 09N13.5W, then continues westward to near 06N23W. The ITCZ extends from 06N23W to 08N38W, then continues west of a surface trough, that runs from 13N39W to 07N40W, from 09N42W to 08N50W to 10N60W. Scattered moderate convection can be found from 07N to 11N between 18W and 26W, from 06N to 12N between 34W and 47W, and from 07N to 11N between 56W and 58W. ...GULF OF MEXICO... High pressure of 1030 mb over the east coast of United States extends into the Gulf of Mexico bringing mostly dry conditions. A few showers and thunderstorms are noted over the SW Gulf and over the NE Yucatan Peninsula. The latter is associated with a surface trough that extends along 88W. Under the influence of the above mentioned high pressure, moderate to fresh E to SE winds and seas of 4 to 6 ft are observed over the E and central Gulf while fresh southerly winds and seas of 5 to 7 ft dominate the western Gulf. For the forecast, high pressure north of the area will support moderate to fresh winds, locally strong in the E Gulf, through the remainder of the week. ...CARIBBEAN SEA... Tropical Depression Twenty-One has dissipated inland over Nicaragua. Please, see the Special Features section above for more information. High pressure of 1030 mb over the east coast of United States is building southward across Cuba and Hispaniola into the northern Caribbean Sea. A surface trough, currently over the Yucatan Peninsula, is generating scattered showers with embedded thunderstorms over the NW Caribbean. A diffluent pattern aloft is helping to induce this convective activity. A few showers and thunderstorms are also noted over the central Caribbean, and the Lesser Antilles. Moderate to locally fresh NE winds are present in the lee of Cuba and Windward Passage, with seas of 4 to 6 ft in the lee of Cuba. Elsewhere, winds are light to gentle with 1 to 3 ft seas. The exception is in the Mona and Anegada Passages, where swell from distant Hurricane Tammy is causing seas of 4 to 6 ft. For the forecast, fresh to occasionally strong winds will prevail in the lee of Cuba and in the Windward Passage through the week. Gentle winds will prevail elsewhere. ...ATLANTIC OCEAN... Please read the Special Features section at the beginning about Hurricane Tammy. A cold front extends from 31N57W across the NW Bahamas into SE Florida. Cold air stratocumulus clouds are seen on visible satellite imagery in the wake of the front. Strong high pressure of 1030 mb over the east coast of United States follows the front. Recent scatterometer data provide observations of fresh to strong northerly winds behind the frontal boundary, and mainly fresh N to NE winds south of the front to the coast of eastern Cuba. Some shower activity is over the SE Bahamas, the Turks and Caicos Islands and eastern Cuba. Outside of the area being affected by Tammy, seas are in the 6 to 9 ft range E of the Bahamas. The remainder of the Atlantic forecast area is under the influence of a 1025 mb high pressure located S of the Azores near 32N29W. This system is producing a gentle to moderate anticyclonic flow. Seas range from 4 to 7 ft over this area. For the forecast W of 55W, Hurricane Tammy is near 24.2N 62.3W at 11 AM EDT, and is moving northeast at 7 kt. Maximum sustained winds are 65 kt with gusts to 80 kt, and the minimum central pressure is 987 mb. Tammy will move to 25.0N 61.2W this evening, 26.7N 59.9W Wed morning, 28.6N 59.1W Wed evening, 30.1N 59.5W Thu morning, weaken as an extratropical cyclone near 31.2N 60.6W Thu evening, and 31.8N 61.6W Fri morning. Tammy will change little in intensity as it moves to near 32.5N 63.5W early Sat. A cold front extending from 31N57W to the central Bahamas will stall tonight then dissipate by Wed. The pressure gradient between this front, Tammy, and high pressure building N of the area will lead to the development of a broad area of NE winds and rough seas across much of the area west of the frontal boundary Tue through the week. $$ GR