[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210531
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 UTC Wed Oct 20 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 0000 UTC surface analysis and satellite imagery through
0515 UTC.

...TROPICAL WAVES...

An eastern Atlantic tropical wave has its axis along 38W from 02N
to 15N, moving westward around 15 kt. Scattered moderate isolated
strong convection is seen from 02N-10N between 30W-40W.

An eastern Caribbean Sea tropical has its axis extending from the
northern Leeward Islands to 14N64W and to inland Venezuela near
07N. It is moving westward 10-15 kt. Isolated showers and
thunderstorms are east of the wave.

Another eastern Caribbean Sea tropical wave has its axis along 69W
south of 21N to inland Venezuela near 08N. It is moving westward
at 10-15 kt. Scattered moderate convection is noted from 16N to
18N between 67W-71W. Isolated showers and thunderstorms are within
120 nm west of the wave from 15N to 16N.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends off the coast of Guinea from
11N15W to 09N20W and to 08N25W. The ITCZ continues from 08N25W to
06N36W. It resumes at 05N39W to 01N46W. Aside from convection
associated to the tropical wave along 38W, scattered moderate
convection is noted from 06N to 08N between 13W-19W and from
01N to 04N between 30W-35W.

GULF OF MEXICO...

High pressure of 1024 mb centered offshore the southeastern
United States near 32N79W is allowing for gentle to moderate east
winds over the eastern Gulf, with light to gentle winds
elsewhere. Seas are 3-5 ft in the eastern Gulf and 1-3 ft in
the western Gulf, with the exception of 2-4 ft seas in the
eastern Bay of Campeche. A weak trough is over the NW Gulf, while
another one extends from near 28N94W to 23N92W. Isolated showers
are possible near these troughs. Scattered showers and isolated
thunderstorms are observed over most of the NE Gulf waters.
Shortwave energy aloft is helping to sustain this activity.

For the forecast, high pressure ridging will dominate the Gulf
waters during the forecast period. Moderate to fresh easterly
winds are expected over the north-central and NE Gulf this
morning and across the southeastern Gulf into Thu. Gentle to
moderate winds will continue elsewhere.

CARIBBEAN SEA...

A pair of tropical waves are moving across the eastern Caribbean.
Please, see the Tropical Waves section for more details.

A weak pressure gradient is providing for only gentle to moderate
trades across the Caribbean. Seas are generally 2-4 ft throughout,
except for higher slighter higher seas of 3-5 ft south of 15N
east of 80W. Scattered showers and isolated thunderstorms are over
the northwestern Caribbean and over the southwestern Caribbean
from 11N to 15N west of 80W. Similar activity is over portions
of western Cuba and northern Haiti. This activity remains under
an area of relatively light winds aloft due to an upper-level
anticyclone that is centered near 18N85W. A jet stream branch
stretches eastward from the south-central Gulf of Mexico to over
Cuba. Disturbances riding along this jet stream branch may be
aiding the convection over western Cuba.

For the forecast, high pressure building north of the area will
support fresh to locally strong trades E of the Windward Islands
into Sun night. During this period, moderate to fresh winds are
expected over the south-central Caribbean, with winds reaching
locally strong in the Venezuela basin. Gentle to moderate
trades are elsewhere.

ATLANTIC OCEAN...

High pressure of 1024 mb centered offshore the southeastern
United States near 32N79W is presently controlling weather regime
over the western part of the area. A cold front extends from near
31N49W to 26N58W, where it transitions to a stationary front to
24N65W. A trough extends from near 25N56W to 22N61W and to 19N64W.
Scattered showers and thunderstorms are seen along and near the
stationary front and along the cold front between 51W-54W.
Scattered showers and isolated thunderstorms are along and near
the trough between 56W-59W, and also over the waters south of 25N
between 68W-77W including some sections of the Bahamas.

Latest ASCAT data passes indicate moderate to fresh northeast to
east winds within 90 to 120 nm north of the front, and light to
gentle east winds elsewhere north of the frontal boundary. Recent
altimeter data noted seas of 4-7 ft north of the cold front and
3-5 ft elsewhere, except for lower seas of 2-4 ft north of 27N and
west of 70W. A tight gradient between high pressure that is
centered near 26N45W and lower pressures to the south near the
ITCZ region has increased the trades to fresh to strong speeds
over the southern part of the area from 08N to 15N between 48W-
54W. Seas are peaking to 8 ft with these winds. This area of fresh
to strong trades is forecast to expand westward and some to the
north over the next couple of days, with seas of 8-9 ft.

The Cumbre Vieja volcano, on the island of La Palma in the
Canary Islands, has been erupting since 19 September 2021. Ash
emission is on-going. Moderate to high volcanic ash is expected
in the vicinity of the volcano. Elsewhere, light volcanic ash
concentration is drifting south. Marine and aviation interests
should monitor this ongoing situation by reading the Volcanic Ash
Advisory issued by Meteo-France at http://vaac.meteo.fr/volcanoes
/la- palma/.

For the forecast west of 65W, high pressure will shift
eastward across the western Atlantic along 31N-32N through early
Fri, producing moderate to fresh winds immediately north of the
trough. Surface troughing will then prevail over the area through
early next week.

$$
Aguirre
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