[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111629
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Mon Oct 11 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 1200 UTC surface analysis and satellite imagery through
1620 UTC.

...TROPICAL WAVES...

A tropical wave is analyzed near 36W/37W, moving west at 10 kt. A
recent scatterometer satellite pass showed a distinct surface
trough in this area, as did recent satellite derived winds in the
low levels of the atmosphere. A few showers may be active from 04N
to 08N between 35W and 39W. This appears to be a fairly shallow
feature, and is in a relatively unfavorable upper environment,
with strong and dry NW winds aloft. This is limiting convective
growth to near the area where the wave interacts with the ITCZ.

A tropical wave located along 55W/56W, moving west at 10 to 15
kt. Low pressure with a surface pressure of 1009 mb is centered
along the tropical wave near 11N55W or about 350 nm east-
southeast of the Windward Islands. The low continues to produce
disorganized cloudiness and thunderstorms. Some slow development
is possible during the next day or two while the system moves
west- northwestward at about 10 to 15 kt toward the Lesser
Antilles. After that time, strong upper-level winds are expected
to limit further development. Regardless of development, the
system could produce locally heavy rainfall and gusty winds across
portions of the central and northern Lesser Antilles on Tue, and
across the Virgin Islands and Leeward Islands on Wed.

Another tropical wave is located over entering the central
Caribbean Sea along 69W/70W, moving west at 15 kt. A few showers
and thunderstorms are active off southeastern Hispaniola, along
the wave axis. This is where the wave is interacting with
divergence aloft on the southeast side of a broad upper low
centered over the Cay Sal area of the Bahamas. The wave axis shows
up well in current satellite derived wind data and 12 UTC
sounding data from Santo Domingo and Curacao.

A fourth tropical wave is near 84W/85W extending southward through
eastern Honduras and eastern Nicaragua, moving west at 15 to 20
kt. This is in an area of deep layer subsidence with strong
northerly winds aloft. Other than a few minor showers off Costa
Rica associated with trade wind convergence, no significant
convection is noted near this tropical wave.

...MONSOON TROUGH/ITCZ...

A monsoon trough extends from the mouth of the Gambia River near
13N16W to 06N25W. A segment of the ITCZ continues from 06N25W to
06N33W. Another ITCZ segment reaches from 06N38W to 03N51W.
Scattered moderate to isolated strong convection is evident from
04N to 07N between 17W and 22W. Convection elsewhere is described
in the Tropical Wave section.

...GULF OF MEXICO...

A trough extends from southwest Florida to western Cuba. Another
trough is analyzed from near Tampa Bay, Florida to 24N86W. Weak
ridging prevails elsewhere across the Gulf. A cluster of
thunderstorms is moving off the Texas coast from Galveston Bay to
the Sabine Pass and Lake Charles area of Louisiana. Moderate to
fresh SE to S winds are noted over the northeast Gulf with 5 to 7
ft seas. Light to gentle E to SE breezes and slight seas are noted
elsewhere.

For the forecast, the ridge will continue to dominate 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
through Thu. Gentle to moderate breezes will persist elsewhere
through Fri.

...CARIBBEAN SEA...

Regional land-based and buoy observations along with a 12 UTC
scatterometer satellite pass confirmed moderate to fresh winds
across the far eastern Caribbean, where the pressure gradient is
tight between two tropical waves and the Atlantic ridge to the
north of the region. Fresh to strong winds and scattered squalls
and tstms are possible in the northern Leewards. Based on recent
ship and buoy observations and an earlier altimeter satellite
pass, seas are 3 to 5 ft in the southeast Caribbean and may be
approaching 5 to 7 ft in the northeast Caribbean. Gentle to
moderate winds and slight to moderate seas are evident elsewhere
across the basin. In addition to the convection extending from
the northern Leeward Islands to southeast Hispaniola, modest
convection is evident north of eastern Panama near 11N78W.

For the forecast, the tropical wave entering the central
Caribbean will continue move across Hispaniola and the central
Caribbean today. The other tropical wave now located along 55W-
56W is expected to approach the central and northern Lesser
Antilles on Tue, and move across the Leeward Islands and Virgin
Islands on Wed. Locally heavy rainfall and gusty winds are
expected with the wave passage. Northerly swell spreading across
the central Atlantic this morning will reach the regional Atlantic waters
and Caribbean passages early Tue.

...ATLANTIC OCEAN...

A broad upper low centered over the Cay Sal area of the Bahamas is
supporting clusters of showers and thunderstorms over much of the
northern and central Bahamas, as well as northeast of the Turks
and Caicos Islands from 23N to 25N between 68W and 72W. An associated
surface trough reaches from 31N78W to a 1011 mb surface low near
27.5N79.5W to the Straits of Florida. Farther east, 1024 mb high
pressure is centered near 34N55W. A swath of moderate to fresh SE
to S winds extends between the high pressure and the trough from
just north of the Leeward Islands to just east of the Bahamas.
Buoy observations hint seas may be as high as 8 ft in this area of
winds north of Puerto Rico, between 60W and 70W south of 23N.

Another upper low is centered near 23N60W with a trough extending
southward to near Barbados. Divergence aloft associated with this
trough is supporting the convection near the tropical wave along
55W/56W, but is also providing shear and deep layer dry air just
to the west of the tropical wave axis. A dying cold front is
analyzed from 32N32W to 28N41W then continues as a trough to
28N53W, south of the high pressure. Light to moderate winds are
noted north of 25N between 35W and 65W, with moderate fresh trades
farther south into the tropics. A a pair of early morning
altimeter passes along with recent buoy observations also show
evidence of northerly swell with wave heights from 8 to 11 ft
north of 25N between 35W and 65W. Seas are 4 to 6 ft elsewhere in
open waters east of 35W. East of 35W, scattered showers and
thunderstorms are evident just ahead of the cold front north of
27N between 30W and 35W. Light to gentle breezes are evident north
of 22N and east of 35W, with mostly moderate trades farther south.
A new tropical wave may be emerging off the coast of West Africa,
and will be evaluated for the next surface analysis at 18 UTC.

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, the trough off the east coast of
Florida will meander today, then drift eastward and weaken
through midweek. Farther south, low pressure is forecast to
develop around mid-week near the southeast Bahamas. Northerly
swell across the central Atlantic will reach waters east of 72W
late tonight through Tue.

$$
Christensen
This weather bulletin was brought to you by:
www.nashvilleweather.net