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NHC Atlantic Tropical Weather Discussion (corrected)

AXNT20 KNHC 240612
TWDAT Tropical Weather Discussion...CORRECTED
NWS National Hurricane Center Miami FL 0605 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 1800 UTC surface analysis and satellite imagery through 2300 UTC. ...SPECIAL FEATURES... Hurricane Tammy is centered near 22.3N 63.6W at 23/2100 UTC or 605 nm S of Bermuda, and moving NNE at 6 kt. Estimated minimum central pressure is 990 mb. Maximum sustained winds are 65 kt with
gusts to 80 kt. Peak seas near the center are estimated at 27 ft.
The seas 12 ft or greater extend outward up to 150 nm from the center. Numerous moderate convection is seen within 240 nm north and east of the center. A turn toward the northeast is expected to
occur by Tue and this general motion should continue through Wed.
On Thu a turn back toward the north and north-northwest is forecast. Some slight strengthening is possible during the next day or so followed by steady weakening. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at the website and the latest Tammy NHC Forecast/Advisory and Public Advisory at for more details. Newly formed Tropical Depression Twenty-One is centered near 11.6N
83.5W at 23/2100 UTC, or about 30 nm SE of Bluefields, Nicaragua,
moving W at 4 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 25 kt with gusts to 35 kt. Peak seas near the center are about 6 ft. Numerous moderate isolated strong convection is occurring within 270 nm of the center in the N semicircle and 75 nm S semicircle. A west to west-northwest
motion is expected until the system moves into Nicaragua and
dissipates. Little change in strength is expected before the
depression moves inland into Nicaragua tonight. Dissipation is
expected on Tuesday. The main impact will be heavy rainfall over
Nicaragua, as well as eastern and southern 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 for more details. Western Atlantic Very Rough Seas: High pressure will move off the
east coast of the United States later tonight, and build north of
the forecast area through midweek. The pressure gradient will
tighten between Hurricane Tammy and the area of building high pressure. The tightening pressure gradient will help to develop a
very large area of strong to near-gale force NE winds and very rough seas of 12 to 17 ft across much of the area from 23N to 31N, between the east coast of Florida and 60W, starting Tuesday 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. ...MONSOON TROUGH/ITCZ... A monsoon trough enters the Atlantic along the coast of west
Africa near the border of Guinea and Guinea-Bissau near 11N15W to
08N20W to 09N24W. The ITCZ extends from 09N24W to 10N33W, then
continues west of a surface trough from 08N39W to 08N44W to
14.5N51W. A surface trough is analyzed from 11N36W to 08N38W to
07N40W. Scattered moderate isolated strong convection is noted
near the ITCZ from 08N to 14N between 41W and 51W. Similar
convection is near the surface trough from 07N to 10N between
34.5W and 38W. ...GULF OF MEXICO... Little to no shower activity is noted across the basin currently. A broad surface ridge dominates the Gulf. Moderate to fresh SE winds and seas of 4 to 6 ft seas are seen over the western Gulf.
Moderate E winds and 2-4 ft seas are over the SE Gulf. The
northeast Gulf is experiencing gentle E winds and 1-3 ft seas. For the forecast, high pressure building north of the area will lead to increasing winds early this week, with fresh to locally strong E winds and building seas through Thu night. ...CARIBBEAN SEA... Please read the Special Features section above for details on
Tropical Depression Twenty-One. Outside of TD Twenty-One,
Scattered showers and tstorms are noted across the western
Caribbean, west of 76W. Moderate to locally fresh NE winds are
present in the NW Caribbean and Windward Passage, with seas 3 to 5
ft. 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, Tropical Depression Twenty-One will move inland
to 12.0N 84.2W Tue morning, and dissipate Tue afternoon.
Otherwise, fresh to occasionally strong winds will prevail in the
lee of Cuba and in the Windward Passage through the week. Winds will briefly increase to fresh to strong south of Hispaniola Wed night and Thu. Elsewhere, gentle winds will prevail. ...ATLANTIC OCEAN... Please read the Special Features section at the beginning about Hurricane Tammy. Winds over 20 kt and/or seas over 8 ft associated
with Tammy prevail from 19N to 28N between 59W and 70W. A weak cold front curves west-southwestward from 31N64W to 29N70W
to the coast of Florida near 27.5N80W. No significant convection is found near the front. A dissipating stationary front extends southwestward from near 31N61W to the SE Bahamas to eastern Cuba.
Scattered moderate convection is noted within 180 nm SE of the
dissipating stationary front, mainly east of 66W. Elsewhere west
of 60W, outside of the area being affected by Tammy, winds are
fresh NE with seas of 5 to 7 ft. A large dome of 1023 mb high pressure near 32N33W is providing gentle to moderate winds across the eastern Atlantic, east of 55W.
Seas range from 4 to 8 ft over this area, except as high as 9 ft in the far east Atlantic, to the north of the Cabo Verde Islands. For the forecast W of 55W, Hurricane Tammy will move to near
24N62W Tue afternoon, 27N59W Wed afternoon, and weaken as an extratropical cyclone near 30N59W Thu afternoon. Tammy will
continue to gradually weaken as it moves to near 32N62W Fri afternoon. Otherwise, see the Special Features section above for a
description of very large seas expected to cover the western half
of the Atlantic, Tuesday afternoon through Friday. $$