[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111028
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 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 0600 UTC surface analysis and satellite imagery through
1015 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 is analyzed along the coast of Guinea near
10N14W and extending to 09N18W. The ITCZ begins near 09N18W and
extends westward to 02N50W. Scattered moderate convection is
observed from 03N to 09N and E of 25W.

GULF OF MEXICO...

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

The basin is in the southwestern periphery of an expansive 1029
mb high pressure system centered 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 depicted 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 1 nm through tonight along the NE Gulf. The surface
ridge extending 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 ahead of the front. Gale force
winds are expected to develop in the wake of the front across the
western Gulf through Sun morning. 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...

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 depicted 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 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 22N. 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 28N71W, 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 52W, extending from 11N to 21N. Satellite imagery show
scattered showers near the trough axis. 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 22N, and mainly gentle to moderate winds N of 22N through
tonight. 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/.

$$
ERA
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