[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121047
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Tue Oct 12 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 0600 UTC surface analysis and satellite imagery through
1030 UTC.

...TROPICAL WAVES...

An Atlantic tropical wave has its axis along 22W, south of 16N
and it is moving W at 10-15 kt. Scattered moderate to isolated
strong convection is observed from 07N to 22N and between 21W and
23W.

Another Atlantic tropical wave has its axis along 41W, south of
17N and it is moving W at 10-15 kt. Isolated showers are noted
near the wave axis, mainly from 05N to 08N. The northern portion
of the wave is surrounded by dry Saharan air, suppressing the
development of showers and thunderstorms.

A third Atlantic tropical wave has its axis along 60W, south of
19N and it is moving W at 10-15 kt. Strong westerly shear is
displacing the convection to the E of the center, especially from
11N to 17N and between 53W and 59W. Satellite-derived wind data
indicate that the tropical wave, located a little over 150 miles
east of the Windward Islands, has become less defined overnight.
While this system continues to produce showers and thunderstorms
primarily east of its center, strong upper-level winds will likely
prevent further development during the next couple of days.
Regardless of development, the system could produce locally heavy
rainfall and gusty winds across portions of the central and
northern Lesser Antilles today. There is a low chance of
development in the next 48 hours and 5 days.

A Caribbean tropical wave has its axis along 73W, south of 21N
and it is moving W at 15 kt. Divergence aloft is helping to
enhance the scattered moderate to isolated strong convection seen
on satellite imagery from 11N to 19N and between 71W to 75W,
impacting Hispaniola and the SE Bahamas. Although environmental
conditions are not forecast to be conducive for development of
this system, a broad area of low pressure, however, is expected to
form near the southeast Bahamas on Wednesday and drift generally
eastward through the end of the week. Regardless of development,
locally heavy rainfall is possible over portions of the Lesser
Antilles, Puerto Rico, and Hispaniola during the next couple of
days. This disturbance has a low chance of development over the
next 48 hours. Please visit hurricane.gov to read the latest
Tropical Weather Outlook from the National Hurricane Center.

A second Caribbean tropical wave has its axis along 88W, south of
20N, extending southward through Honduras and El Salvador, and it
is moving W at 15 kt. No deep convection is noted near the
tropical wave.

...MONSOON TROUGH/ITCZ...

A monsoon trough extends from the coast of Guinea-Bissau near
11N15W to 06N30W. The ITCZ continues from 06N30W to 06N40W, then
resumes W of a tropical wave near 06N43W to 06N52W. Scattered
moderate convection is noted from 03N to 08N between 17W and 29W
and between 37W and 51W.

...GULF OF MEXICO...

A dry airmass dominates the Gulf of Mexico resulting in fairly
tranquil weather conditions across the basin. A surface trough
cross the Florida peninsula into the NW Caribbean along 82W, but
no deep convection is associated with this feature. A weak 1015 mb
high pressure over the NE Gulf results in gentle to moderate
anticyclonic winds prevailing across the basin. However, fresh
NE-N winds are noted within 60 nm of the N and W coast of the
Yucatan peninsula.

For the forecast, a weak and narrow ridge extends from the eastern
U.S. southwestward to the N central Gulf and will influence the
Gulf waters during the next several days. Moderate to fresh
southerly winds are expected over the western Gulf between the
ridge and lower pressure over the Southern Plains and northern
Mexico tonight through Thu. Gentle to moderate breezes will
persist elsewhere through Fri. A cold front enter the NW Gulf Fri
night.

...CARIBBEAN SEA...

Outside of the active tropical wave described in the Tropical
Waves section, the rest of the Caribbean Sea has fairly tranquil
weather conditions. Fresh trades are noted over the E Caribbean
and the Gulf of Honduras, mainly within 90 nm of the coast of
Honduras. Moderate or weaker winds are present in the rest of the
basin. Seas of 3-6 ft are found in the central, E and SW
Caribbean, while 1-3 ft are prevalent elsewhere.

For the forecast, a tropical wave near 60W is expected to approach the
Lesser Antilles this morning and move near the Virgin Islands by
tonight. Expect thunderstorms and strong gusty winds with the
wave passage. Northerly swell will continue to impact the regional
Atlc waters and Caribbean passages today through Wed.

...ATLANTIC OCEAN...

A broad mid to upper level low near the Cay Sal Bank in the
Bahamas is interacting with two surface troughs, one located in
the NW Bahamas and another one extending from the SE Bahamas to
near 26N70W, resulting in scattered moderate to isolated strong
convection from 20N to 30N between 64W to 78W. Farther E, a
surface trough enters the tropical Atlantic near 31N29W and
extends to 24N42W. This feature is only generating a few showers
near the trough axis. The rest of the basin enjoys fairly tranquil
weather conditions under a dry environment.

The pressure gradient between the 1022 mb high pressure over the
N Atlantic and the lower pressures in the E Caribbean results in
fresh SE winds from the E Greater Antilles to 28N and between 55W
and 72W. Moderate to fresh trades are noted S of 20N and between
the coast of Africa to the Lesser Antilles. Moderate or weaker
winds are found in the remainder of the basin. A northerly swell
results with seas of 8-11 ft is found N of 23N and between 30W and
63W, while seas of 5-8 ft prevail elsewhere in the tropical
Atlantic.

The Cumbre Vieja volcano, that is on the island of La Palma in
the Canary Islands, has been erupting since 19 September 2021.
Currently, significant volcanic ash is seen in the vicinity of
the volcano spreading eastward. 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/.

For the forecast west of 65W, a surface trough stretching across
Florida will continue to linger in the area and weaken through
Wed. This will lead to scattered showers and thunderstorms off the
Florida coast. Otherwise, Atlc high pres extends across into the
area and will help maintain quiescent conditions through Fri.
Farther south, low pressure is forecast to develop around mid-
week near the SE Bahamas. Northerly swell across the central Atlc
will continue across the waters E of 72W through tonight.

$$
AReinhart
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