[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201013
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Sat Nov 20 2021

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 0600 UTC surface analysis and satellite imagery through
1000 UTC.

...MONSOON TROUGH/ITCZ...

The monsoon trough remains over Africa. The ITCZ begins near 04N16W
and continues to 07N33W, then resumes W of a surface trough near
07N40W to 05N50W. Scattered moderate to isolated strong convection
is observed from 02N to 07N between 12W and 25W. Similar convection
is noted from 05N to 11N between 26W and 37W. The latter is mainly
associated with a surface trough that extends from 16N31W to 04N38W.

GULF OF MEXICO...

A nearly stationary front extends from Tampa Bay, Florida to the
central Gulf near 25N90W to south of Veracruz, Mexico. Winds have
diminished below gale force over the SW Gulf. An earlier altimeter
pass indicated seas up to 12 ft off Veracruz, Mexico in association
with the gale force winds. Currently, scatterometer data show fresh
to strong NE winds over the eastern half of the Gulf, with strong
NW winds over the SW Gulf. The exception being the NW Gulf where
winds have decreased to fresh to moderate. Seas of 7-10 ft are
occurring in the SW Gulf, while 3-6 ft prevail elsewhere.

Multilayered clouds, with embedded showers and isolated thunderstorms,
continue to dominate most of the Gulf waters due to the presence
of strong upper-level SW winds ahead of an upper-level trough that
crosses the NW Gulf.

For the forecast, the previously-mentioned front will drift south
while dissipating this weekend. High pressure will dominate the Gulf
region in the wake of the front. Another cold front will enter the
northwest Gulf early on Mon, and move south of the basin by Mon evening.
Fresh to strong northerly winds are expected behind the front, but mainly
over the eastern Gulf, through Tue night. High pressure will follow
the front.

CARIBBEAN SEA...

Recent satellite-derived wind data show mainly gentle to moderate
trade winds across the basin with the exception of fresh winds
near the coast of Colombia and in the Gulf of Venezuela. Seas of
5-7 ft prevail in the south-central Caribbean, with 3-5 ft
elsewhere, except in the lee of Cuba and in the Gulf of Honduras
where seas of 1-3 ft are found.

Scattered showers are thunderstorms are affecting the Caribbean
plains of Nicaragua. A diffluent pattern aloft is helping to
sustain this convective activity. Elsewhere, shallow moisture
embedded in the trade wind flow will continue to move across the
region producing isolated to scattered passing showers. A weak
surface trough is analyzed across the Leeward Islands and is
producing some shower activity.

For the forecast, mainly gentle to moderate trades will prevail
across much of the Caribbean Sea during the next several days. A
cold front will reach the Yucatan Channel by Mon evening, and
extend from eastern Cuba to the Gulf of Honduras by late Tue.
Fresh to locally strong winds and building seas are expected behind
the front.

ATLANTIC OCEAN...

Strong SW winds aloft continue to support abundant cloudiness,
with some shower activity over Florida and the SW N Atlantic,
including also parts of the Bahamas. A cold front extends from
31N70W to near Cape Canaveral, Florida. Fresh to strong NE winds
are noted per scatterometer data on either side of the frontal
boundary N of 27N. A surface trough is over the NW Bahamas along
76W/77W. A cluster of moderate to isolated strong convection is
just E of the central Bahamas on the E side of the trough axis. A
shear-line remains over the Atlantic forecast waters and now extends
from 30N32W to 25N40W to 23N50W. A few showers are noted along
this shear-line. Satellite-derived wind data indicate that fresh
to strong NE-E winds are found behind the shear line, with seas of
8-11 ft based on altimeter data.

Farther east, a 1010 mb low pressure is located near 27N30W. A
surface trough extends from the low center to near 19N39W. Low
level clouds, with embedded showers, are associated with these
features.

Northerly swell, generated by a low pressure system located N of
area, will reach the forecast waters late today, building seas to
10-14 ft roughly N of 29N between 25W and 40W by Sun morning.

The Cumbre Vieja volcano, on the island of La Palma in the Canary
Islands, has been active for two months(since 19 September 2021).
An ash emission is ongoing. Medium ash concentration is noted in
the vicinity of the volcano, low elsewhere. Marine and aviation
interests should monitor this ongoing situation by reading the
Volcanic Ash Advisory issued by Meteo-France, at
http://vaac.meteo.fr/volcanoes/la-palma/.

For the forecast W of 65W, the cold front extending from 31N70W
to near Cape Canaveral, Florida will remain across the northern
forecast waters this weekend, before lifting north ahead of a
another cold front that will move off the northeast Florida coast
on Mon. The second front will reach from near Bermuda to eastern
Cuba by late Tue. Fresh to strong northerly winds and building
seas are expected behind the fronts. Winds may reach gale force
behind the second front.

$$
GR
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