[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 182312
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Sun Dec 19 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
2300 UTC.

...MONSOON TROUGH/ITCZ...

The ITCZ extends from the coast of Sierra Leone near 08N13W to
05N30W to 08N36W, then continues west of a surface trough from
08N40W to near the Venezuela-Guyana border. The surface trough
runs from 12N37W to 05N38W. Isolated showers are near the trough
axis. Scattered moderate convection is from 05N-07N between
20W-30W.

...GULF OF MEXICO...

High pressure located over the western Atlantic near 29N63W
extends a ridge across Florida into the Gulf of Mexico. Gentle to
moderate anticyclonic flow is noted over the Gulf waters under
the influence of this system. Seas are generally in the 3-5 ft
range. A cold front is approaching the coast of Texas generating
numerous showers and thunderstorms. Similar convective activity
is seen ahead of the front over parts Alabama and Louisiana.
Scattered showers and isolated thunderstorms are flaring up over
the eastern Gulf and also over the west-central Gulf. Upper
diffluence is helping to induce this convection.

For the forecast, the cold front will move off the Texas coast
this evening, bringing strong to near gale-force winds to the NW
Gulf and along the coast of Mexico Sun into Mon. The front will
move slowly until a low pressure forms along the frontal boundary
in the central Gulf on Mon, then moves northeastward into the SE
U.S. Tue, dragging the cold front across the Gulf as it does.
Winds and seas will subside Tue night through Thu in the wake of
the front, as weak high pressure builds in across the Gulf. Corpus
Christi has issued a gale warning for frequent gusts to gale
force for the coastal waters through early Sun morning.

...CARIBBEAN SEA...

The tight pressure gradient between high pressure located over
the western Atlantic near 29N63W and the Colombian/Panamanian
low is resulting in fresh to strong winds across the central
Caribbean Sea just S of Jamaica, with the strongest winds
occurring offshore NW Colombia. Satellite derived wind data
confirmed the presence of these winds. Fresh to locally strong
winds are present across the remainder of the E and central
Caribbean, with moderate to fresh E to SE winds over the NW
Caribbean. Seas of 9-12 ft dominate the waters E of the Lesser
Antilles and in the south-central Caribbean, with seas of 6-8 ft
elsewhere S of 18N and E 82W. Seas of 8-9 ft in NE swell are
affecting the Atlantic passages E of La Mona Passage. In the NW
Caribbean, seas are in the 3-5 ft range.

Scattered showers and isolated thunderstorms are seen over NE
Honduras and northern Nicaragua as well as over parts of the Gulf
of Honduras. Elsewhwere, patches of low level moisture, embedded
in the trade wind flow, are observed elsewhere producing isolated
to scattered passing showers.

For the forecast, the high pressure over the western Atlantic
will support fresh to strong trades over the central and E
Caribbean and tropical N Atlantic this weekend. The high will
move east for the start of next week, leading to weaker trades.
Large N to NE swell will continue in the tropical N Atlantic as
well as Mona and Anegada Passages through Mon. Looking ahead, a
cold front should move through the Yucatan Channel late Tue and
may reach Honduras and Nicaragua by Thu.

...ATLANTIC OCEAN...

The above mentioned high pressure located near 29N63W dominates
the central and western Atlantic, the Bahamas and the State of
Florida. Farther E, a cold front enters the forecast waters near
31N18W then continues SW to near 21N30W. A well defined shearline
begins at 22N30W and stretches westward along 17N45W to 18N60W.
Fresh to strong NE winds are on the north side of the shearline
W of 35W, with mainly moderate NE winds in the south side of the
shearline. The pressure gradient between the high pressure and
lower pressures in the vicinity of the ITCZ also supports fresh
to locally strong NE-E winds from 10N-16N between 40W and the
Lesser Antilles. Seas of 9-12 ft in NE swell are in this region.
A pair of altimeter passes indicate seas of 9-13 ft in the wake
of the front between 40W-55W.

For the forecast W of 65W, high pressure over the western Atlantic
is inducing fresh to strong trades near the Greater Antilles and
mainly gentle winds elsewhere. These conditions will prevail
through early Sun, before the high shifts to the east and winds
relax. A cold front will move off the SE U.S. coast Sun night and
continue eastward, bringing strong to near gale force winds on
both sides of the front mainly north of 29N. Low pressure is
likely to move northeastward off the SE U.S. coast Tue, bringing
another potential for strong to near gale force winds on Wed and
Thu. Seas of 8-9 ft in NE swell affecting the waters S of 25N
and E of the Bahamas will subside on Sun.

Large N swell impacting the Atlantic forecast waters W of 35W will
gradually subside beginning on Sun.

$$
GR
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