[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 222201
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Sun Nov 22 2020

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 1800 UTC surface analysis and satellite imagery through
2200 UTC.

...TROPICAL WAVES...

A tropical wave extends from near Grand Cayman Island to western
Panama, moving westward at 10 to 15 kt. The wave combined with a
middle level inverted trough is producing scattered moderate
convection over the western Caribbean, mainly off Nicaragua and
in the Gulf of Honduras.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coast of Guinea near 11N15W
to 09N20W. The ITCZ continues from 09N20W to 03N50W. A few showers
are observed from 08N-10N between 23W-25W, and from 05N- 07N
between 40W-43W.

GULF OF MEXICO...

A weak surface ridge extends north of the Gulf from the
1023 mb high pressure over north Georgia to the Lower
Mississippi Valley. The high pressure is weakening ahead of a
cold front approaching the area from the northwest. A surface
trough extends off the western coast of the Yucatan peninsula,
reaching into the northwest Gulf. This pattern is supporting
gentle to moderate NE to E winds across the Gulf currently. Seas
are 2 to 4 ft except for a tongue of 4 to 6 ft seas reaching from
the Yucatan Channel into the central Gulf due to southerly swell
moving northward from the northwest Caribbean Sea. No
significant shower or thunderstorm activity is noted at this time
across the Gulf of Mexico.

For the forecast, the cold front will reach the northern Gulf
tonight into Mon and quickly dissipate. High pressure will follow
the front. Fresh southerly return flow will set up over the
western Gulf Mon night through Tue night ahead of the next cold
front forecast to reach the northern Gulf late on Wed, then stall
and lift northward Thu. Looking ahead, a third and stronger cold
front is expected to move across the Gulf waters during the
upcoming weekend.

CARIBBEAN SEA...

Divergence aloft on the southeast side of a broad mid to upper
level trough north of the area is interacting with the tropical
wave moving into the western Caribbean to support scattered
showers and thunderstorms over much of the western Caribbean and
south of Haiti. Scatterometer satellite data from 15 UTC and
recent buoy observations indicate mostly gentle trade wind flow
across the basin, except for moderate trade winds over the
eastern Caribbean, due to the influence of the subtropical ridge
to the north. These moderate trade winds are supporting 5 to 7 ft
seas over the eastern Caribbean. Larger seas, of 7 to 9 ft, are
impacting the Atlantic waters east of the Leeward and Windward
Islands, and possibly the adjacent Atlantic passages. Lingering
SE swell is supporting 4 to 6 ft combined seas in the northwest
Caribbean. Seas are 3 to 5 ft elsewhere.

For the forecast, fresh easterly winds and seas in the 8-9 ft
range will continue to impact the waters east of the Lesser
Antilles through Mon night. Building high pressure north of the
area will bring an increase in winds and seas across the south-
central Caribbean Tue through Thu. Fresh to strong NE winds are
expected across the Windward passage Tue night through Thu night.

ATLANTIC OCEAN...

East of 65W, a mid to upper level low centered near 27N70W is
supporting a surface trough reaching from the Turks and Caicos
Islands to near 30N66W. The surface trough is well defined in
buoy observations and earlier scatterometer satellite data.
Moderate to fresh SE winds and a few showers are possible within
300 nm east of the trough axis. Seas reach 6 to 8 ft in this area
as well with a component of NE swell. Moderate NE to E winds are
noted west of the trough axis, with 5 to 7 ft seas in open
waters. For the forecast, there is a slight chance that the
surface trough could briefly develop into a subtropical storm
while it moves northeastward during the next day or two before it
merges with a cold front on Tue. The front will move into the NW
waters on Mon and progress through the area through the middle
of week while gradually weakening.

Farther east, recent scatterometer data showed a pair of troughs
east of 40W and south of the Azores, with 15 to 20 kt winds
between each trough and ridging farther norther. The ridging is
supporting generally moderate trade winds elsewhere.

$$
Christensen
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