[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181809
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Mon Dec 18 2023

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 1200 UTC surface analysis and satellite imagery through
1630 UTC.

..SPECIAL FEATURES...

Western Atlantic Gale Warning:
A cold front extends southwestward from off the U.S. Mid-Atlantic
coast across 31N71W and the southeast Bahamas to near the Windward
Passage. Scattered to numerous moderate convection is occurring
near and up to 180 nm east of the front north of 21N, including
the southeast Bahamas and Turks and Caicos Islands. Gradient
remains tight between this front and a broad surface ridge
extending southwestward from a strong 1047 mb high at the north-
central Atlantic. This is maintaining near-gale to gale with
locally strong gale-force southerly winds and seas of 12 to 18 ft
just east of the front, north of 25N between 64W and 71W. This
winds and seas will gradually shift eastward along with the front
through today and this evening. As the front stalls and weakens
Tuesday morning, marine conditions should begin to improve.

Central Atlantic Gale Warning:
Tight gradient between a strong 1047 mb high at the north-central
Atlantic and a 1013 mb low near 24N44W is sustaining near-gale to
gale NE winds with 12 to 18 ft seas north of 23N between 40W and
60W. This low is expected to slowly drifts westward and prolong
gales and peak seas of 14 to 21 ft in this general area through
Tuesday.

Please read the latest NWS High Seas and Offshore Waters
Forecasts issued by the National Hurricane Center at
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and
https://www.nhc.noaa.gov/marine/offshores.php for more details on
both Gale Warnings.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic near Monrovia, Liberia, then
extends westward to near 04N16W. An ITCZ continues westward from
04N16W across 04N30W to 04N46W. Scattered to numerous moderate
convection is noted up to 170 nm north, and 120 nm south of the
ITCZ east of 34W. West of 34W, widely scattered moderate
convection is occurring up to 50 nm along either side of the ITCZ.
There is no significant convection near the monsoon trough.

Convergent winds north of the East Pacific monsoon trough over
Panama are causing scattered showers at the southwestern Caribbean
waters adjacent to the Costa Rica and Panama.

...GULF OF MEXICO...

A surface trough reaches southwestward from central Florida to the
central Gulf. A very dry air mass continues to dominate the entire
Gulf. Moderate to fresh NNW winds and seas of 6 to 8 ft exist
across the central and eastern Gulf. Gentle N winds and 4 to 6 ft
seas in moderate easterly swell prevail for the western Gulf,
including the Bay of Campeche.

For the forecast, fresh NW to N winds continue across the eastern
Gulf and will gradually diminish today. High pressure will
dominate the weather pattern across the Gulf waters through Tue,
then strengthen north of the region Wed through Thu, producing
fresh to strong NE to E winds across the eastern Gulf, including
the Straits of Florida.

...CARIBBEAN SEA...

A stationary front runs southwestward from near the Windward
Passage to the southwestern basin. Scattered showers and isolated
thunderstorms are noted up to 120 nm along either side of this
boundary, including waters near Jamaica and the Windward Passage.
Convergent E to SE winds farther east of the front are producing
similar weather across eastern Cuba and the southeastern basin
near the Windward Islands. Convergent northerly winds are inducing
scattered showers from the Gulf of Honduras to near the Cayman
Islands. Fresh to strong northerly winds and seas of 6 to 8 ft are
evident behind the stationary front across the western basin,
including the Yucatan Channel and Gulf of Honduras. Gentle to
moderate ENE to SE winds and 4 to 6 ft seas prevail for the rest
of the Caribbean Basin.

For the forecast, the stationary front will reach from central
Hispaniola to 11N78W this evening before dissipating across the
Caribbean. Fresh to strong northerly winds and seas to 9 ft are
expected in the wake of the front through Wed. High pressure will
build southeastward across the western Atlantic Wed night through
Fri to produce fresh to strong NE winds in the lee of Cuba and
the Windward Passage. At the same time, fresh to locally strong
trades are expected in the south-central basin, including the
Gulf of Venezuela.

...ATLANTIC OCEAN...

Please read the Special Features section at the beginning on two
ongoing Gale Warnings.

Other than the cold front mentioned in the Special Features
section, a warm front runs southeastward from northwest of Bermuda
across 31N66W to north of the Leeward Islands at 23N63W. Widely
scattered showers are noted up to 40 nm along either side of this
feature. A stationary front extends southwestward from near the
Azores across 31N36W to 22N53W. Scattered showers are found up to
70 nm along either side of this boundary. A surface trough reaches
southwestward from south of this stationary front at 28N39W
through the 1013 mb low mentioned in the Special Features section
to 19N50W. Aided by divergent flow east of a pronounced upper-
level low near 21N47W, scattered to numerous moderate convection
is occurring from 15N to 26N between 41W and the low/surface
trough. Farther southwest, convergent trades are generating
scattered showers and isolated thunderstorms from 12N to 15N
between 46W and the Windward Islands. These showers can produce
locally heavy downpours near the Windward Islands through Tuesday.

Behind the cold front, moderate to fresh NW to W winds and seas
of 8 to 14 ft in residual easterly swell are present north of
24N, including the northwest Bahamas. Farther south west of the
cold front, gentle to moderate NW to W winds and 4 to 7 ft seas
are seen from 20N to 24N, including the central and southeast
Bahamas. Outside of the Gale Warning areas, fresh to strong NE to
SE winds and 8 to 12 ft seas dominate north of 20N between the
1013 mb low/surface trough and cold front. For the eastern
Atlantic, moderate to fresh E to SE winds and seas at 8 to 10 ft
are noted north of 15N between the Africa coast and the 1013 mb
low/surface, including the Canary and Cabo Verde Islands. For the
tropical Atlantic, gentle to moderate NE to SE winds and seas of 5
to 8 ft in moderate northerly swell exist from 05N to 20N/15N
between the central Africa coast and Lesser Antilles. Light to
gentle winds and 4 to 7 ft seas in moderate mixed swell prevail
for the rest of the Atlantic Basin.

For the forecast W of 55W, gales ahead of the front will persist
through tonight. The front is expected to reach from 31N68W to
Haiti this evening, from 31N66W to the northern coast of
Hispaniola near 19N70W by Tue evening, and from 31N61W to eastern
Hispaniola by Wed evening. Strong high pressure will build into
the western Atlantic behind the front Tue night through early Thu
to produce fresh to strong winds.

$$

Chan
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