[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 131035
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Wed Oct 13 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 28W, south of 18N
and it is moving W at 10-15 kt. Scattered moderate to isolated
strong convection is observed from 04N to 12N and between 27W and
31W.

Another Atlantic tropical wave has its axis along 49W/50W, south
of 18N and it is moving W at 15 kt. Scattered moderate to
isolated strong convection is noted where the wave interacts with
the ITCZ from 05N to 12N and between 48W and 52W. The northern
portion of the wave is surrounded by dry Saharan air and subsident
northerly flow aloft, suppressing the development of showers and
thunderstorms.

A Caribbean tropical wave has its axis along 65W, south of 20N,
extends from the Virgin Islands to E Venezuela, and it is moving
W at 10-15 kt. Scattered moderate to isolated strong convection is
seen on satellite imagery from 15N to 20N and between 63W to 65W.
Overnight scatterometer satellite pass show fresh to strong SE-S
winds within 170 nm to the E of the wave axis, mainly from 15N and
20N.

A second Caribbean tropical wave has its axis along 80W, south of
20N and it is moving W at 10-15 kts. No deep convection is noted
in association with the wave as it moves across very dry airmass.

...MONSOON TROUGH/ITCZ...

A monsoon trough extends from the coast of Senegal near 11N16W to
05N30W. The ITCZ continues from 05N30W to 05N40W to 07N49W, then
continues W of a tropical wave near 05N51W to the coast of
Suriname near 06N54W. Scattered moderate convection is noted along
the monsoon trough from 04N to 09N between 15W and 28W. Scattered
moderate to isolated strong convection is noted along the ITCZ
from 06N to 10N between 33W and 54W.

...GULF OF MEXICO...

A weak ridge over the eastern United States extends to the Gulf of
Mexico and maintains tranquil weather conditions across the basin.
The pressure gradient between the ridge and lower pressures across
the southern United States and northern Mexico results in fresh SE
winds across the western Gulf waters, especially W of 94W. Seas in
this region are 3-6 ft. Moderate or weaker anticyclonic winds
with seas of 1-3 ft are prevalent elsewhere in the Gulf.

For the forecast, high pres extends extends weakly 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 through Thu. Gentle to moderate breezes will
persist elsewhere through Fri. A cold front enter the NW Gulf Fri
night with fresh to strong northerly winds following it. The front
will reach central Florida to western Bay of Campeche Sun morning
with moderate to fresh N-NE winds across most of the Gulf.

...CARIBBEAN SEA...

An upper level trough off the SE United States extends to the NW
Caribbean Sea allowing for scattered showers and isolated
thunderstorms from the coast of Colombia to Hispaniola, between
71W and 76W. A surface trough extends from southern Florida to
the Gulf of Honduras and a few shallow showers are seen near the
trough axis. The rest of the basin remains fairly quiet outside of
the tropical wave in the E Caribbean previously described in the
Tropical Waves section. Fresh trades were noted overnight within
150 nm of the coast of NE Venezuela, including the waters
surrounding the ABC islands. Moderate or weaker trades prevail
elsewhere. Seas of 3-5 ft are occurring in the E, central and SW
Caribbean, while 1-3 ft are present elsewhere.

For the forecast, a tropical wave along 65W is approaching the Virgin
Islands and Puerto Rico. This wave will continue to bring active
weather across the extreme NE Caribbean and adjacent Atlc waters
today. Northerly swell will subside across the regional Atlc and
Caribbean passages through tonight. Low pres is expected to
develop E of the southern Bahamas on Thu and drift eastward into
the weekend. This will weaken the pressure gradient across the
Caribbean basin leading to tranquil marine conditions.

...ATLANTIC OCEAN...

Overnight scatterometer satellite data depicted a well-defined
surface trough extending from near the Windward Passage to
29N71W. This feature is interacting with an upper level trough
located to the west, producing a large area of scattered showers
and isolated thunderstorms, mainly from 20N to 31N and between 63W
and 72W. There was also fresh to strong cyclonic winds within 100
nm of the coast of Hispaniola. The other feature of interest in
the tropical Atlantic is a 1002 mb low pressure located just
north of our area, but a surface trough extends south to 26N46W.
Scattered moderate convection is observed on satellite imagery
from 25N to 31N between 40W and 51W. Scatterometer satellite data
indicate fresh to strong cyclonic winds N of 28N and between 44W
and 55W. Fairly tranquil weather conditions and moderate or weaker
winds prevail elsewhere in the basin.

Widespread northerly swell continues impact the region, reaching
8-11 ft mainly north of 15N between 30W and 65W. Seas of 5-8 ft
are found elsewhere.

The Cumbre Vieja volcano, 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
drifting southward closer to the surface. Marine and aviation
interests should monitor this ongoing 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, high pressure centered over the
central Atlantic will shift slowly E and weaken through the end of
the week. A surface trough extends from the southern Bahamas to
28N71W. A low pressure is expected to develop along the trough by
Thu as it drifts eastward over the next few days. This system will
continue to produce very active weather and impact the regional
waters through Thu. Northerly swell across the regional waters
will continue to subside today.

$$
AReinhart
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