[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201048
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Sun Dec 20 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 0600 UTC surface analysis and satellite imagery through
1030 UTC.

...SPECIAL FEATURES...

Gulf of Mexico Gale Warning: Near gale to gale force south to
southwest winds are occurring over the NW Gulf within about 90
nm southeast of a 1014 mb low pressure system that is near
29N91W, with a trailing cold front that extends from it to 26N94W
and to inland Mexico at 23N98W, and also within 60 nm southeast
of the squall line segment that extends from near 27N91W to
26N93W. These conditions are forecast to diminish by early this
afternoon as the low pressure reaches to just south of the western
Florida panhandle, with the cold front extending from it to near
25N91W and to the SW Gulf. Please read the latest High Seas
Forecast at https://www.nhc.gov/text/MIAHSFAT2.shtml for more
details.

West Atlantic Gale Warning: A cold front will move across the west
Atlantic starting on Monday. Gale force SW winds are expected to
develop as the front approaches the area and then moves east on
Monday. These conditions will dissipate by Monday night. Please
read the latest High Seas Forecast at
https://www.nhc.gov/text/MIAHSFAT2.shtml for more details.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coastal sections of Sierra
Leone near 08N13W to 07N16W, then transitions to the ITCZ to
07N16W to the coast of Brazil near 04N51W. Scattered moderate
convection is within 120 nm north and 60 nm south of the ITCZ
between 25W-45W.

GULF OF MEXICO...

Please see Special Features section above for details on an
ongoing Gale event over a section of the NW Gulf.

A positively-tilted upper shortwave trough stretches from eastern
Arkansas southwestward to eastern Texas. This feature is driving
a cold front that extends from a 1014 mb low near 29N91W, to
23N98W. A vigorous pre-frontal squall line is analyzed from
29N90W to 25N94W. Scattered to numerous moderate convection is
noted north of 23N between 85W-95W. This activity is capable of
producing strong gusty winds and numerous lightning strikes.

The pressure gradient between the high pressure over the west
Atlantic and lower pressure over the Gulf is supporting moderate
to fresh winds across the basin. Seas are in the range of 3-5 ft,
except for higher seas of 4-6 ft in the NW Gulf.

As for the forecast: The high pressure over the eastern Gulf
will continue to shift eastward through Sun night in the response
to eastward advancement of the low pressure and cold front. The
front is forecast to reach from the central Gulf Coast to the
western Bey of Campeche on Sun, and from southwest Florida to the
Yucatan peninsula on Mon before exiting the southeastern Gulf
early on Mon. Expect for the present ongoing shower and
thunderstorm activity to gradually shift to the eastern Gulf
through tonight. Moderate to fresh southeast winds are expected
in the NW Gulf on Wed. By Thu, a strong cold front is forecast to
move across the basin, with the possibility of gale force
northwest to north winds following in behind it over the SW and
west-central Gulf waters.

CARIBBEAN SEA...

Latest scatterometer data depicts fresh to strong northeast to
east winds over the south-central Caribbean. Fresh northeast winds
are noted south of Hispaniola and over the Windward Passage.
These winds are the result of a tight gradient between high
pressure well north of the area along the U.S. Mid-Atlantic coast
and lower pressure that is typically over NW Colombia and
southwestern Caribbean. These winds will continue into this
morning as the high pressure remains in place. Scattered showers
are noted moving quickly over the Greater Antilles and adjacent
waters.

As for the forecast: High pressure north of the area will continue
to support moderate to fresh trade winds across much of the area.
Highest winds and seas will continue to be in the southern
Caribbean, near the coast of Colombia, pulsing at nighttime
through the forecast period. A cold front will slide southward
into the NW Caribbean by the end of the week enhancing winds/seas.

ATLANTIC OCEAN...

A cold front extends from near 32N46W to 26N55W, where it
transitions to a stationary front to 22N75W. Scattered showers are
noted along the cold front. Mainly moderate northerly winds are
noted in the wake of the front, with an area of fresh winds just
to the north of the southeastern Bahamas as were detected by an
ASCAT pass from last night. Strong high pressure is building in
over the western Atlantic behind the front. A surface ridge
prevails over the east Atlantic, anchored by a 1025 mb high
pressure center located near 30N25W. Fresh trade winds are along
the southern periphery of the ridge affecting the Cabo Verde
Islands and regional waters were seen in a partial ASCAT pass from
last night.

As for the forecast: The tail end of the stationary front will
dissipate this morning, while the cold front will continue to push
eastward and dissipate through the next 24-36 hours. The next
cold front will move off the Florida coast on Mon, reach the
southern Bahamas and southern Cuba by Tue, and continue moving
eastward on Wed. Strong to gale force winds will develop ahead of
the front off the Florida coast and north of the Bahamas on Mon.
Fresh to strong winds will prevail behind the front. By the end of
the week, a strong cold front will push off the northeast Florida
coast enhancing winds and convection.

$$
ERA
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