[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 110425
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 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 0000 UTC surface analysis and satellite imagery through
0425 UTC.

...MONSOON TROUGH/ITCZ...

The monsoon trough remains mostly confined to the African
continent, reaching the coast of Guinea near 10N13W and extending
to 08N17W. The ITCZ begins near 08N17W and extends westward to
04N30W and then to the coast of Amapa near 02N50W. Scattered
moderate to isolated strong convection is observed from 02N to 09N
and E of 27W.

GULF OF MEXICO...

The Gulf of Mexico is in the southwestern periphery of an
expansive 1029 mb high pressure system located to the SE of Nova
Scotia in the NW Atlantic. Dry continental air continues to
dominate the region, maintaining tranquil weather conditions. The
pressure gradient between the subtropical ridge and lower
pressures over Texas and northern Mexico result in moderate to
fresh southerly winds, especially W of 87W. A recent scatterometer
satellite pass even showed a small area of strong southerly winds
in the NW Gulf. Seas of 4-7 ft prevail in the central and western
Gulf, while seas of 2-4 ft are prevalent elsewhere. The highest
seas are occurring in the NW Gulf.

For the forecast, areas of marine fog will lower visibility to less
than one nm tonight and Sat night along the NE Gulf. A high
pressure ridge extending from the Atlantic to the central Gulf
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 tonight 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 tight pressure gradient due to the strong ridge north of the
Greater Antilles and lower pressures over northern South America
result in strong to near gale-force trades across the south-
central Caribbean Sea as shown in a recent scatterometer satellite
pass. The strongest winds are occurring offshore NW Colombia.
Fresh to locally strong trades are present in the north-central
Caribbean Sea, with the strongest winds observed offshore southern
Hispaniola and in the Windward Passage. Seas of 7-10 ft prevail
in the central Caribbean Sea, with the highest seas occurring
offshore NW Colombia. The rest of the basin enjoys tranquil
weather conditions, moderate to locally fresh trades and 3-7 ft
seas.

For the forecast, the aforementioned pressure gradient 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 through the forecast period,
resulting in pulsing fresh to locally strong northeast winds in
the Windward Passage, the lee of Cuba and south of Hispaniola
through Wed night.

ATLANTIC OCEAN...

High pressure dominates most of the tropical Atlantic. A strong
subtropical ridge is positioned off Nova Scotia in the NW
Atlantic, while a second robust subtropical ridge is anchored off
the Azores in the NE Atlantic. The pressure gradient between the
subtropical ridges and lower pressures over NW Africa and the
deep tropics result in fresh to strong easterlies, mainly south
of 25N. Strong E-NE winds are noted at the entrance of the
Windward Passage. The strongest winds are occurring off the
Morocco coast and in the waters surrounding the Canary Islands.
Seas of 8-12 ft are found E of 50W, with the highest seas
occurring offshore Morocco.

A weak shear line extends from 31N55W to 29N71W, passing about
200 nm south of Bermuda. A recent scatterometer satellite pass
depict a small area of fresh E winds north of the shear line. Seas
of 4-8 ft are present W of 60W. A surface trough is analyzed
along 51W, extending from 09N to 21N. Satellite imagery show a
few showers and isolated thunderstorms near the trough axis,
especially S of 13N. The rest of the tropical Atlantic enjoys
fairly tranquil weather conditions, moderate or weaker winds and
5-8 ft seas.

For the forecast west of 65W, high pressure will continue to
build across the region producing moderate to fresh NE to E winds
S of 20N, and mainly gentle to moderate winds N of 20N 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/.

$$
DELGADO
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