[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111657
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 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 1200 UTC surface analysis and satellite imagery through
1655 UTC.

...SPECIAL FEATURE...

Gulf of Mexico Gale Warning: A strong cold front will move over
the NW Gulf today. Gale force winds are expected to develop in the
wake of the front beginning this afternoon over the NW Gulf, then
developing over the Bay of Campeche near Veracruz as the front
moves E through Sun morning. Seas will build to 10 ft in the wake
of the front within the strongest winds. Please refer to the
latest High Seas Forecast product issued by the National Hurricane
Center at the website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic waters through the coast
of Guinea near 11N15W to 09N20W. The ITCZ continues near 09N20W
and extends westward to 02N50W. Scattered moderate convection is
observed from 03N to 14N and E of 25W. Another area of scattered
showers is noted north of the ITCZ to 06N between 34W and 45W.

GULF OF MEXICO...

Refer to the section above for details on the Gale Warning in
effect for the western Gulf.

As of 15Z, a cold front enters the NW Gulf of Mexico from the the
Texas/Louisiana border near 30N94W to 27N97W. Scattered showers
and strong NE winds are observed behind the front. The remainder
of the basin is dominated by the southwestern periphery of an
expansive 1031 mb high pressure system centered in the NW
Atlantic, which is maintaining dry, tranquil weather conditions.
The pressure gradient between the cold front and surface ridging
is producing moderate to fresh southerly winds, especially W of
84W. A recent scatterometer satellite pass depicted a small area
of strong southerly winds in the SW Gulf south of 22N. Seas of 4-6
ft prevail in the central and western Gulf, with the highest seas
occurring in the NW Gulf behind the aforementioned front.
Elsewhere, seas are 2-4 ft.

For the forecast, areas of marine fog will lower visibility to
less than one nm this morning and once again tonight along the NE
Gulf. The high pressure ridge extending from the Atlantic to the
central Gulf will gradually shift eastward through this afternoon
in response to a strong cold front that will move over the NW Gulf
today. Moderate to fresh southerly return flow will set-up across
the western Gulf tonight ahead of the front. Gale force winds are
expected to develop in the wake of the front across the western
Gulf beginning this afternoon and continue through Sun morning.
Seas will build to 10 ft in the wake of the front within the
strongest winds. The front will weaken as it reaches from central
Florida to the SW Gulf Sun and dissipate on 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...

A tight pressure gradient between strong ridging north of the
Greater Antilles and lower pressures over northern South America
is producing generally fresh to strong trades in the eastern and
central Caribbean Sea, including southern Hispaniola and the
Windward Passage. The strongest winds are observed in
scatterometer data offshore NW Colombia. 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 fresh trades, and 3-7 ft seas.

For the forecast, the aforementioned pressure gradient between
the ridge across the northern Caribbean and the
Colombian/Panamanian low will continue to support fresh to strong
easterly trades over the south-central Caribbean through the
weekend and early next week. 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...

A cold front is analyzed near 31N52W, transitioning to a weak
shearline from 28N55W to 28N68W. A surface trough extends from
11N54W to 22N52W. Satellite imagery reveals scattered showers near
the trough axis. High pressure dominates the remainder of the
tropical Atlantic with a strong subtropical ridge centered in the
NW Atlantic and a second robust Azores high pressure in the NE
Atlantic. Satellite derived winds measured fresh to strong
easterlies, mainly south of 25N as a result of the pressure
gradient between the subtropical ridges mentioned and lower
pressures over NW Africa and the deep tropics. Strong E-NE winds
at the entrance of the Windward Passage are evident in
scatterometer data with the strongest winds observed off the
Morocco coast north of 30N. Seas of 8-12 ft are found E of 51W,
with the highest seas occurring offshore Morocco. Elsewhere in the
tropical Atlantic, fairly tranquil weather conditions prevail
with 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 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/.

$$
Nepaul
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