[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 221759
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 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 1200 UTC surface analysis and satellite imagery through
1730 UTC.

...TROPICAL WAVES...

The axis of a tropical wave is south of Puerto Rico, moving
westward at 10 to 15 kt. Latest sounding data shows from the
Leeward Islands and Puerto Rico shows fairly persistent SE flow
through the lower to mid levels of the atmosphere. This indicates
the tropical wave is likely weakening, ahead of ridging building
over the northeast Caribbean.

A slightly more defined tropical wave extends from 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 W Caribbean, mainly west
of 79W.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coast of Guinea near
10N15W to 09N20W. The ITCZ continues from 09N20W to 03N50W.
A few showers are observed from 06N-08N between 36W-39W.

GULF OF MEXICO...

A weak surface ridge extends north of the Gulf from the Carolinas
to the Lower Mississippi Valley. This 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, a 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 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. Recent scatterometer satellite data and 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 to 9 ft
range will continue to impact the waters east of the Leeward and
Windward Islands and adjacent Atlantic passages 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 occasionally strong NE winds are
expected across the Windward Passage Mon 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 30N67W. The surface trough is well defined in
buoy observations and recent 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. 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
off northwest Africa 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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