[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 081805
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Fri Oct 8 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
1705 UTC.

...SPECIAL FEATURES...

An elongated area of low pressure located more than 200 miles off
the coast of South Carolina is producing disorganized showers and
thunderstorms well to the east of its center of circulation. Satellite
images and surface observations indicate that the low pressure
system located a couple of hundred miles east of the coast of
South Carolina is gradually becoming better defined. Although the
associated shower and thunderstorm activity is currently
disorganized, environmental conditions could briefly become
marginally conducive for the low to acquire subtropical
characteristics by Saturday night and early Sunday. By early next
week, the low is expected to interact with a frontal boundary,
which should end the opportunity for any subtropical or tropical
formation. The low is forecast to meander offshore the Carolinas
today, and then slowly move back toward the west-northwest and
northwest on Saturday, bringing the system closer to the coast of
North Carolina. The disturbance has a medium chance of development
over the next 48 hours. Please read the latest Tropical Weather
Outlook at hurricanes.gov and the High Seas Forecast from the
Ocean Prediction Center at ocean.weather.gov

...TROPICAL WAVES...

An Atlantic tropical wave has its axis along 38W, south of 16N,
and it is moving W at 15 to 20 kt. Deep convection near the
southern portion of this wave is mainly associated with the
nearby ITCZ. The northern portion is devoid of deep convection due
to dry Saharan air.

A Caribbean tropical wave has its axis along 67W, south of 19N,
extending from Puerto Rico to Venezuela, and it is moving W at 15
to 20 kt. Scattered moderate to isolated strong convection is
noted from 12N to 16N and between 64W and 71W.

...MONSOON TROUGH/ITCZ...

The monsoon trough remains over Africa while the ITCZ extends
westward from the Sierra Leone coastline at 09N13W to 07N25W and
to 06N38W. The ITCZ then continues from 06N39W to 02N50W.
Scattered moderate to isolated strong convection is occurring
within 300 nm on both sides of the ITCZ between 13W and 48W.

...GULF OF MEXICO...

The previously stationary front in the NE Gulf of Mexico is now on
the move as a cold front, extending from a 1017 mb low pressure in
SW Georgia to 28N87W. A pre-front trough is analyzed from the Big
Bend area of Florida to 27N88W and a few showers and isolated
thunderstorms is noted within 100 nm to the E of the trough axis.
Another surface trough is present in the SW Gulf of Mexico,
extending from 24N92W to 18N95W. Scattered moderate convection is
seen on satellite imagery S of 24N and between 92W and 96W. Dry
continental air continues to percolate into the NW Gulf, allowing
for tranquil weather conditions. A weak pressure gradient
dominates most of the basin, resulting in gentle to moderate
cyclonic winds. However, fresh to locally strong NW winds are
occurring within 60 nm of the coast of Veracruz, especially from
19N to 21N. Seas of 3-5 ft are present in the Bay of Campeche and
SE Gulf, while 1-3 ft are prevalent elsewhere.

For the forecast, the frontal boundary and surface troughs
continue to support scattered showers and tstms over the NE and SW
Gulf. The pressure gradient between high pressure along Mexico
and the trough in the Bay of Campeche continue to support fresh to
strong northerly winds over the Veracruz adjacent waters,
forecast to diminish to moderate winds early this evening. Weak
high pressure will build across the E half of the basin this
upcoming weekend into early next week, and support moderate to
locally fresh return flow W of 90W Sun through Tue night.

...CARIBBEAN SEA...

The E Pacific monsoon trough enters the SW Caribbean Sea through
the coast of Costa Rica and extends to NW Colombia. Scattered
moderate convection is noted within 60 m of the coasts of
Nicaragua, Costa Rica, Panama and NW Colombia. Outside of the
active tropical wave mentioned in the Tropical Waves section, the
rest of the Caribbean enjoys fairly tranquil weather conditions.
Recent scatterometer satellite data show fresh to strong trades in
the south-central Caribbean, with the strongest winds occurring
within 60 nm of the coast of Colombia. Gentle to moderate trades
prevail elsewhere in the basin. Seas of 5-8 ft are occurring in
the central and SW Caribbean, with the highest seas off the coast
of NW Colombia. Seas of 3-6 ft are prevalent elsewhere.

For the forecast, moderate to locally fresh trades are expected
across the eastern half of the Caribbean and the tropical Atlantic
waters through the forecast period as surface riging builds NE of
the area and both a tropical wave and a low level disturbance
moves across the area over the weekend. The tropical wave near 67W
is forecast to move over the central basin tonight and Sat and
across the W Caribbean on Sun. The low level disturbance is
forecast to move across the Lesser Antilles Sat evening with
active weather extending to Puerto Rico and the Virgin Islands Sun
evening through Tue night. The disturbance is forecast to be over
the Central Caribbean Wed morning, affecting Hispaniola and
adjacent waters.

...ATLANTIC OCEAN...

A 1025 mb subtropical ridge is centered near the Azores. A
surface trough extends from 27N58W to Hispaniola and it is
producing a few showers and isolated thunderstorms nears the
trough axis. Another surface trough associated with the remnants
of an old frontal boundary extends from 26N42W to 30N51W.
Scattered moderate convection is noted from 25N to 31N and between
40W and 55W. Recent scatterometer satellite data indicate that
fresh to locally strong winds are found near the strongest
convection.

A third surface trough extends from 16N53W to 10N56W
and it is generating widespread showers and isolated
thunderstorms, mainly from 09N to 14N and between 52W and the
Lesser Antilles. Satellite-derived wind data depict fresh to
locally strong trades S of 22S and between 40W to the Lesser
Antilles. Fresh to locally strong N-NE winds are also occurring
from 18N to 28N and E of 25W, including the waters surrounding the
Canary Islands. Moderate or weaker winds are prevalent elsewhere
in the tropical Atlantic. Seas of 3-6 ft prevail W of 60W, while
7-10 ft are present S of 20N and between 40W and the Lesser
Antilles. Seas of 5-8 ft are found elsewhere.

The Cumbre Vieja volcano, that is on the island of La Palma in
the Canary Islands, has been erupting since 19 September at 1410
UTC. An ash plume is partially identifiable on satellite imagery
drifting westward toward the Tenerife Island. Top is estimated
with Webcams at 11,000 ft. Marine and aviation interests should
monitor this on-going situation, by reading the Volcanic Ash
Advisory, that is issued by Meteo-France, at
http://vaac.meteo.fr/volcanoes /la-palma/. The next advisory
will be issued no later than 08/2100 UTC.

For the forecast W of 65W, an elongated area of low pressure
located more than 130 nmi off the coast of South Carolina continue
to support scattered showers and tstms across the offshore waters
N of the Bahamas. By Sunday, environmental conditions could
briefly become marginally conducive for some subtropical
development of the low. However, by early next week, the low is
expected to interact with a frontal boundary, which should hinder
the opportunity for any subtropical or tropical formation.
Regardless of development, the low will continue to support active
weather over the northern offshore waters today, with this
activity extending across the Bahamas during the remaining
weekend.

$$
DELGADO
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