[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 102347
TWDAT

Tropical Weather Discussion NWS National Hurricane Center Miami
FL 0005 UTC Sat Dec 11 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 1800 UTC surface analysis and satellite imagery through
2340 UTC.

...MONSOON TROUGH/ITCZ...

The monsoon trough remains confined to the African continent,
reaching inland Sierra Leon near 08N12W. The ITCZ begins near
06N13W and extends westward to 05N30W and then southwest to the
coast of Brazil near 02N45W. Scattered moderate isolated strong
convection is from 03N to 10N between 10W and 30W.

GULF OF MEXICO...

High pressure ridging into the area dominates the weather
pattern, suppressing any significant convection. However,
shallow moisture and return flow is supporting areas of dense
fog in the NW and north-central gulf offshore waters as
indicated by surface observations and low level precipitable
water microwave data. The pressure gradient between the ridge
and lower pressure over Texas is leading to moderate to fresh S
to SE winds across most of the basin with locally strong winds
in the NW gulf. Seas are in the 3 to 5 ft range being the
highest seas in the NW basin where the strongest winds lie.

For the forecast, areas of marine fog will lower visibility to
less than one nm tonight and Sunday night along the northern and
eastern Gulf. Visibility will gradually deteriorate through the
morning hours before improving Saturday morning. The high
pressure ridge will gradually shift eastward through Sat
afternoon in response to a strong cold front that will move over
the NW Gulf on Sat. Moderate to fresh southerly return flow will
set-up across the western Gulf beginning late Fri ahead of the
front. Fresh to strong northerly winds and building seas are
expected in the wake of the front through Sat night. The front
will weaken as it reaches from central Florida to the SW Gulf Sun
and dissipate by Mon. Fresh to strong east winds will spread
westward through the Straits of Florida and to the eastern Gulf S
of 26N Mon through Tue night along with building seas.

CARIBBEAN SEA...

The gradient between the subtropical high and low pressure over
Colombia is maintaining enhanced easterly trade wind flow through
the basin. Winds are moderate to fresh in the eastern and NW Caribbean
with 5-6 ft seas. Winds are fresh to strong in the central
Caribbean with 6-7 ft seas. Fresh to strong NE winds are also
funneling through the Windward Passage with seas to 6 ft. Dry and
stable atmospheric conditions are limiting any significant
convection in the basin.

For the forecast, the pressure gradient between the ridge across
the northern Caribbean Sea and the Colombian/Panamanian low will
continue to support fresh to strong easterly trades over the
south-central Caribbean through the weekend. Moderate to fresh
trades will prevail elsewhere. High pressure will continue to
strengthen over the western Atlantic today resulting in fresh to
locally strong northeast winds in the Windward Passage, the lee of
Cuba and south of Hispaniola through Wed night.

ATLANTIC OCEAN...

A weakening stationary front extends from 31N55W to 29N60W where a
shear line continues SW along 29N66W to 29N69W. Surface high
pressure dominates elsewhere. Gentle to moderate E-NE winds are
predominant in the SW Atlantic waters while fresh trades dominate
the central tropical and subtropical waters with seas in the 7 to
9 ft range. In the E Atlantic, a tighter pressure gradient
continue to support fresh to strong NE winds N of the Cape Verde
Islands with seas in the 8 to 11 ft range.

For the forecast west of 65W, the front will dissipate tonight.
High pressure will build across the region in the wake of the
front, producing moderate to fresh NE to E winds S of 22N, and
mainly gentle to moderate winds N of 22N through Sat night. The
next cold front will move off the northeast Florida coast Sun, and
reach from near 31N65W to South Florida by Sun night. This front
is forecast to dissipate over the southeastern waters on Mon. High
pressure behind the front will bring fresh to strong northeast to
east winds mainly across the waters south of 27N by Mon night.
These conditions are expected to last through Tue night.

The Cumbre Vieja volcano, on the island of La Palma in the Canary
Islands, has been erupting since 19 September 2021. Low ash
concentrations are expected in the vicinity of the volcano with
very low concentrations to the southwest. 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/.

$$
Ramos
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