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Atlantic Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1250 PM EST Wednesday Nov 20 2019

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 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis.

Based on 1200 UTC surface analysis and satellite imagery through 1720 UTC.

Active and Developing Storms
Tropical Storm Sebastien is near 21.1N 61.7W at 20/1500 UTC, or about 191 nm NNE of the northern Leeward Islands. Sebastien is moving W at 6 kt. The estimated minimum central pressure is 1002 mb. Maximum sustained winds are 45 kt with gusts to 55 kt. Numerous moderate with scattered strong convection extends outward to 200 nm in the SE quadrant. Scattered moderate convection is elsewhere within 300 nm in the SE quadrant. Sebastian will turn to the north later today, then turn to the northeast with an increase in forward speed is expected tonight and Thursday. Some strengthening is forecast during the next 48 hours. Sebastien is expected to become an extratropical cyclone in a couple of days and be absorbed by a cold front on Friday. The Public Advisories for Sebastien are available via the WMO header WTNT35 KNHC and the AWIPS header MIATCPAT5. The Forecast/Advisories are available via the WMO header WTNT25 KNHC and the AWIPS header MIATCMAT5 or visit

Tropical Waves
An Atlantic Ocean tropical wave is along 44W from 14N southward, moving W at 10-15 kt. Scattered showers are noted from 07N-12N between 41W- 46W.

A Caribbean Sea tropical wave is along 74W from 20N southward, moving W at 5-10 kt. Isolated showers are seen in SW Haiti near the wave axis.

Monsoon Trough And Intertropical Convergence Zone - ITCZ
(The ITCZ is also known by sailors as the doldrums)
The monsoon trough passes through the coastal plains of southern Sierra Leone near 07N12W to 05N18W. The ITCZ continues from 05N18W to 04N29W to 07N43W, then W of a tropical wave near 07N45W to the coast of Suriname near 06N55W. Scattered moderate convection is seen from 02N- 09N between 10W- 28W.

Discussion: Gulf Of Mexico
A 1021 mb surface high is near 27N87W and is ridging across the basin. As such, relatively dry air covers most of the area. The latest ASCAT pass shows that gentle to moderate anticyclonic winds cover the basin.

High pressure over the central Gulf will shift eastward today. Fresh to locally strong SE return flow will develop over the NW Gulf tonight into Thursday ahead of a cold front moving over Texas. The front will move into the NW Gulf late Friday night, cross the region Saturday through Sunday, then weaken and stall over the southern Gulf Sunday night.

Discussion: Caribbean Sea
A surface trough extends across eastern Honduras into the NW Caribbean, from 16N84W to 19N85W. Showers are seen within 70 nm on either side of the trough. Meanwhile, a 1012 mb low is located over the Turks and Caicos Islands near 21N71W with a trough that extends along the low from 18N76W to 24N67W. Scattered showers and thunderstorms are seen along this trough, including over Hispaniola, the Windward Passage, and just east of Jamaica. Isolated showers are seen moving across the Lesser Antilles, Puerto Rico and the USVI. Strong upper level ridging will inhibit any deep convection. The latest ASCAT pass shows moderate to fresh northerly winds in the western Caribbean, with calm to light trades across the rest of the basin.

Tropical Storm Sebastien will turn northward later today and move away from the area. Fresh NE winds will prevail across most of the western Caribbean through Friday morning, with the strongest winds expected through the Windward and Mona passages Thursday night as high pressure builds north of the region.

Discussion: Atlantic Ocean
A cold front enters the forecast waters near 31N67W and stretches southwestward toward the central Bahamas near 25N76W to northwest Cuba near 23N82W. Showers are within 50 nm of this boundary. A pre-frontal trough is noted from 26N69W to 35N61W. Scattered moderate convection is ahead of this trough from 27N-38N between 56W-65W. An upper level low is noted near 17N41W. With support from the ITCZ, scattered showers are noted from 09N-16N between 21W-41W. The latest ASCAT pass shows fresh to strong NW winds in the western Atlantic, N of 28N and W of 68W.

In the far NE portion of the area, a cold front extends southwestward from a 1016 mb low near 31N16W to 27N30W. Scattered showers are seen within 50 nm of the front. Latest ASCAT pass shows gentle to moderate N winds behind the front. Surface ridging dominates the rest of the area from a 1028 mb high near 32N42W.

Tropical Storm Sebastien will turn northward later today and move to 22.0N 61.7W this evening, 23.7N 60.2W Thu morning, 26.3N 57.2W Thu evening, then become extratropical as it merges with a cold front near 29.8N 52.5W Friday morning. Elsewhere, the cold front in the western/central Atlantic will continue moving southeastward across the region through Thursday. High pressure will build across the northern waters Thursday through Saturday, then shift eastward Saturday night through Sunday as the next cold front moves off the SE U.S. coast.

Forecaster: Amanda Reinhart, National Hurricane Center

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