[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 131759
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Sun Dec 13 2020

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 32N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 1200 UTC surface analysis and satellite imagery through
1745 UTC.

...SPECIAL FEATURES...

Gulf of Mexico Gale Warning: A strong cold front will move into
the NW Gulf tonight. Behind this front, strong cold air advection
will induce northwest to north gale force winds to 35 kt over the
NW Gulf overnight tonight along with seas building to 11 ft. This
same surge of cold air will also bring similar northerly gale
force winds, but slightly stronger, up to 40 kt, over sections of
the western and SW Gulf Mon through Mon evening, with strong
north winds elsewhere over the western Gulf. Seas are forecast to
reach 11 ft in the SW Gulf. Winds and seas will decrease Tue as
high pressure moves over the area. Please read the latest High
Seas Forecast at https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for
more details.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from the coast of Sierra Leone
near 08N13W to 06N21W, where latest scatterometer data indicates
that it transitions to the ITCZ to 06N21W to 04N38W to 03N51W.
Scattered moderate to isolated strong convection is within 90 nm
either side of the ITCZ between 37W-39W. Scattered moderate
convection is seen within 180 nm south of the trough axis between
east of 20W to just inland the coast of Africa.

GULF OF MEXICO...

Please see the Special Features section for details on a forecast
Gulf of Mexico gale warning.

As of 15Z, a cold front extends from the Florida panhandle near
Panama City southwest to 29N87W, where it becomes stationary to
29N90W. From there it transitions to a warm front northwestward
to along and just inland the Louisiana coast to inland
northeastern Texas. An area of scattered showers and thunderstorms
moving northeastward extends from inland Texas near Corpus
Christi northeastward to the Louisiana border and offshore for
about 60 nm. Isolated showers, mostly light, are along and near
the stationary and cold fronts. Moist southerly flow resulting in
patches of low clouds and stratus are over the rest of the Gulf.
Isolated showers are possible with some of these cloud patches.
Otherwise, a 1020 mb high center is analyzed over north-central
Florida, with a a ridge extending west-southwestward to near
25N90W.

As for the forecast: The warm front will continue to lift
northward today, with fresh southerly winds developing in its
wake. A more significant cold front will move into the Gulf
tonight, then move across much of the basin Mon into Tue. Strong
N winds will spill behind the front and gales will develop over
portions of the western and southwestern Gulf Mon and Mon
evening. Wind and seas decrease Tue as high pressures builds in.
The next front will move into the western Gulf Tue night and
across the Gulf by Thu. Northerly gales will briefly occur
offshore Veracruz, Mexico Wed afternoon.

CARIBBEAN SEA...

Upper-level ridging covers the western Caribbean and Central
America. Water vapor imagery depicts moderate subsidence inducing
dry sinking air and rather stable atmospheric condition across
these sections of the sea. An upper-level trough axis extends from
near 30N58W to the eastern part of the Caribbean. At the surface,
a trough has moved to just inland the northeastern part of the
Yucatan Peninsula. Latest satellite imagery shows patches of low-
level moisture in the form of scattered to broken clouds moving
westward in the trade wind flow across the basin. Isolated showers
are possible with some of these clouds. Latest partial ASCAT data
reveals generally moderate to fresh trades over the central part
of the sea, with the exception of fresh to strong trades south of
about 14N between 74W-79W and to near the coast of Colombia.
Gentle to moderate trades are elsewhere across the sea. Seas are
in the range of 4-7 ft, except for higher seas in the range of 6-9
ft in the south-central section of the sea, where the fresh to
strong winds are occurring.

As for the forecast: The fresh to strong trades in south-central
Caribbean will pulse nightly through Mon along the Colombian
coast. High pressure will weaken across the western Atlantic
early Mon through Wed allowing for weaker winds across the entire
basin. A weakening cold front will move slowly southeastward
across the Yucatan Channel and western Cuba late on Thu.

ATLANTIC OCEAN...

A cold front is analyzed from near 32N25W to 29N35W, then
weakening stationary to 27N49W. The boundary then transitions to
a shearline to near 24N59W. ASCAT data from this morning revealed
a large area of fresh to strong northeast to east winds north of
stationary front and shearline to 30N and between 45W-58W.
Mainly fresh northeast to east winds are east of 45W north of
the stationary and cold fronts. A surface trough is along a
position from near 24N57W to 18N59W. This feature lies to
southeast of a rather robust upper-level trough that stretches
from near 32N54W southwestward to 24N60W and to the eastern
Caribbean Sea. Upper-level divergence southeast of this feature
is helping to promote an increasing area of rain with embedded
scattered moderate convection over the area from 20N-29N and
between 50W- 59W. Weak low pressure is forecast to develop
along the surface trough near 24N by early Tue.

Elsewhere across the eastern waters, moderate to large northwest
swell remains in the waters roughly north of 20N and east of 67W,
where seas are in the 8-12 ft. This area of swell is forecast to
gradually shrink into the early part of the week as it shifts to
the south and southeastward.

A surface trough east of northern Florida extends from 32N79W to
29N80W. Light northwest winds are west of the trough. Isolated
showers are near this trough. The morning ASCAT data showed
moderate to fresh northeast to east winds between 58W-68W, gentle
to moderate winds between 68W-75W and light to gentle winds west
of 75W.

A 1032 mb high center is analyzed north of the area at 35N52W,
with a ridge extending west-southwestward to just east of the
trough that is east of northern Florida. High pressure covers the
discussion area outside the aforementioned described features.

As for the forecast: The high pressure ridging east of northern
Florida will shift eastward through Mon in response to the
next cold front that will move over the northwest waters Mon
afternoon. The front is forecast to reach a position from near
Bermuda to Palm Beach, Florida, Tue morning before is becomes
stationary. Strong southwest winds will develop Mon offshore the
northern Florida coast ahead of the front. The next front will
move off the northern Florida coast Wed night and reach from
near 32N69W to central Florida Thu evening.

$$
Aguirre
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