[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210551
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 UTC Mon Dec 21 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 0000 UTC surface analysis and satellite imagery through
0530 UTC.

...SPECIAL FEATURES...

Atlantic Gale Warning: A cold front is west of the area over the
Gulf of Mexico and as of 03Z it extends from a 1013 mb low
pressure over Apalachee Bay southwestward to 24N87W and to
near 19N94W. The low is forecast to strengthen as it moves
northeastward into the western Atlantic. Fresh to strong winds are
expected on either side of the front early this morning. Winds
ahead of the front will reach gale force north of 28N and within
about 90 nm east of the front by early this afternoon. Seas are
expected to build up to 12-13 ft within the area of gale force
winds. The low pressure will move well north of the area later
today as the cold front progresses quickly eastward across the
western Atlantic. By around 03Z tonight, winds will diminish below
gale force ahead of the front expected to reach from near Bermuda
to central Cuba at that time. Please read the latest High Seas
Forecast at https://www.nhc.gov/text/MIAHSFAT2.shtml for more
details.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from the border of Sierra Leone
and Guinea near 09N13W to 08N17W, where a Sun evening ASCAT
indicated that it transitions to the ITCZ to 05N30W and to
05N40W and to the coast of Brazil near 03N51W. Scattered moderate
to isolated strong convection is within 60 nm either side of
the ITCZ between 21W-28W. Scattered moderate convection is within
120 nm north and 60 nm south of the ITCZ between 32W-39W and also
well south of the ITCZ within 30 nm of a line from 03N14W to
03N19W.

GULF OF MEXICO...

As mentioned above under SPECIAL FEATURES, as of 03Z a cold front
extends southwestward from a 1013 mb low pressure that over
Apalachee Bay southwestward to 24N87W and to near 19N94W. A pre-
frontal trough extends from near Venice, Florida to near 25N85W.
NWS Doppler Radar and satellite imagery show scattered showers
and a few thunderstorms are seen within 60 nm southeast of the
trough east of the trough. A 1021 mb high center is analyzed over
the far NW Gulf near 28N96W. Latest ASCAT data shows fresh
northwest winds behind the front to near 90W and fresh to strong
northwest to north winds along and just offshore Veracruz, Mexico.
Moderate to fresh winds are west of 90W, except for light to
gentle winds west of 93W. Cold-air stratocumulus clouds are in the
wake of the front east of 93W. Low-level scattered to broken
clouds continue to be banked up along the Sierra Madre Mountains
of Mexico.

As for the forecast: The cold front will exit the southeastern
Gulf this morning followed by fresh northwest to north winds.
High pressure centered over the NW Gulf will shift eastward to
northeast of the Gulf by late Tue allowing for southerly flow
fresh winds to develop over western Gulf and gentle to moderate
east winds to exist across the rest of the Gulf. A strong cold
front is forecast to move across the area on Thu followed by
possible gale force winds in the SW Gulf.

CARIBBEAN SEA...

ASCAT data from last night shows fresh to strong trade winds over
the south-central Caribbean and in the Gulf of Venezuela. Fresh
northeast winds are present south of Hispaniola. These winds are
the result of the pressure gradient between high pressure located
over the western Atlantic and lower pressure associated with the
Colombian/Panamaniam low. These winds will persist over the south-
central Caribbean during most of the forecast period.

Patches of low-level moisture, embedded in the trade wind flow,
are noted moving westward across the basin mainly north of about
14N. Isolated to scattered passing showers are possible with some
of these clouds. Northeast winds over the southeastern Bahamas
continue to advect small patches of low-level moisture, with
possible isolated showers, toward the coast of eastern Cuba.

As for the forecast: The cold front that is presently moving
across the eastern and central Gulf of Mexico is forecast to reach
the Yucatan Channel and western Cuba this morning. It is forecast
to extend from central Cuba to northern Belize by tonight, then
gradually weaken from eastern Cuba to the Gulf of Honduras on Tue.
Another and stronger cold front is expected to reach the Yucatan
Channel and western Cuba by Thu night. Fresh to strong northerly
winds will follow this front.

ATLANTIC OCEAN...

A cold front is forecast to bring strong to gale force winds
across the western Atlantic on Mon. Please see the Special
Features section for more details on this upcoming event. Fresh
to strong southerly winds in advance of this upcoming cold front
are already present over the waters east of NE Florida to near
75W. Scattered showers and thunderstorms are moving northeastward
over these waters.

Farther east, a cold front enters the central part of the area
near 32N35W and extends to 27N46W, where it becomes stationary
to 24N57W and dissipating stationary to near 22N69W. Pockets of
low-level moisture, with possible isolated to scattered showers,
are observed to be along and within 120 nm north of the frontal
boundary, except within 30-60 nm either side of the boundary
between 55W-59W. Scattered to broken low clouds, with isolated
showers, are over and near the Bahamas. Latest buoy and ASCAT
data indicates mainly moderate to locally fresh winds northeast
to east winds north of the stationary front to near 29N and
between 47W- 57W. Gentle to moderate northeast to east winds are
elsewhere north of the stationary frontal boundary.

A ridge prevails over the east Atlantic, anchored by a 1029 mb
high pressure center analyzed over the Madeira Islands. The
gradient between it and lower pressure to its south is allowing
for generally fresh trade winds to exist from about 13N-24N and
east of 35W to include the area of the Cabo Verde Islands and
surrounding waters.

As for the forecast: The stationary frontal boundary will
weaken and dissipate by this evening. A cold front is forecast to
move off the Florida coast today, extend from the southeastern
Bahamas to southern Cuba by Tue, and continue moving eastward on
Wed. Gale force winds will develop ahead of the front off the
Florida coast and north of the Bahamas today. Fresh to strong
winds are expected behind the front. By the end of the week, a
strong cold front will push off the northeast Florida coast
enhancing winds and convection.

$$
Aguirre
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