[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200603
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
0545 UTC.

...TROPICAL WAVES...

The axis of a tropical wave is near 33W from 02N to 14N. It is
moving westward around 15 kt. Some slight cyclonic turning is
noted east of the wave near 03N32W. Scattered moderate to isolated
strong convection is within 120 nm west of the wave from 07N to
09N. Scattered moderate convection is within 60 nm east of the
wave from 07N to 08N.

The axis of a tropical wave is near 56W south of 19N to inland
Suriname. It is moving westward around 15 kt. This wave is
noticeable in the GFS 700 mb streamlines. The CIRA LPW animation
imagery shows a moisture maximum trailing this wave east to 52W.
Within this area of moisture scattered showers and isolated
thunderstorms are noted from 08N to 10N. A dry air slot precedes
the wave west to 59W. The A recent ASCAT pass indicates a
northeast to southeast wind shift across the wave axis with speeds
of gentle to moderate. A pocket of fresh to strong east-
southeast winds is east of the wave axis from 08N to 11N between
53W-54W.

The axis of a tropical wave is along 64W south of 19N to inland
Venezuela, moving westward at 10-15 kt. The GFS 700 mb streamlines
capture this wave in a subtle way. Scattered showers and a few
thunderstorms are seen east of the wave axis to 62W and from 11N
to 15N.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends off the coast of Africa near the
border of The Gambia and Senegal at 12N16W to 09N21W. The ITCZ
continues from 09N21W to 06N27W and to 03N44W. It resumes just
to the west of the tropical wave that is near 33W to 02N43W.
Aside from convection associated to the tropical wave near 33W,
scattered moderate to isolated strong convection is north of the
ITCZ from 05N-07N between 35W-39W. Scattered moderate convection
is within 120 nm south of the ITCZ between 23W-27W.

GULF OF MEXICO...

A 1023 mb high center is located just north of the area near
32N80W. A rather extensive surface trough extends from the
northwest Gulf of Mexico near 28N94W to 25N92W and to the eastern
Bay of Campeche near 18N93W. Moderate to fresh easterly winds are
noted over the basin north of 27N between 88W and 94W, and east
of 88W as well due to the pressure gradient between the trough and
high. Seas are 3-6 ft across these same waters. Mainly light to
gentle winds and seas of 2-4 ft continue elsewhere.

For the forecast, a ridge will dominate the Gulf of Mexico waters
during the forecast period. Moderate to fresh easterly winds are
expected over the north-central and NE Gulf waters through Wed,
and across the southeastern Gulf through Wed night. Gentle to
moderate winds will prevail elsewhere.

CARIBBEAN SEA...

A weak pressure pattern exists across the Caribbean waters with
gentle to moderate trades prevailing, except light to gentle south
of 11N in the SW Caribbean. Seas are mainly 2-4 ft, except 1-3 ft
in the western Caribbean south of 18N. Satellite imagery shows
enhanced cloudiness and convection of the scattered moderate to
isolated strong type intensity covering most of the western
Caribbean waters from about 11N to 22N and west of 80W. This
activity is under a large upper-level anticyclone providing light
winds and ventilation over it. Upper-level disturbances riding
along the southern branch jet stream that stretches across the
crest of the aforementioned anticyclone may be further aiding this
convection to some extent. Expect for this convection to change
little through at least Wed. Scattered showers and a few
thunderstorms are over the extreme southwestern Caribbean south of
11N and west of 76W, mainly due to atmospheric instability from
the eastern segment of the eastern Pacific monsoon trough that
protrudes into that part of the Caribbean. Isolated showers and
thunderstorms are over the Windward Passage. Isolated showers are
over some sections of the northeast Caribbean waters.

For the forecast, high pressure building north of the area will
bring fresh to locally strong trades east of the Windward Islands
Wed through Sun. 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
tradewinds will prevail elsewhere.

ATLANTIC OCEAN...

A cold front extends from near 31N55W to 26N65W, where it becomes
stationary to 24N72W and dissipating to the central Bahamas. A
recent ASCAT pass shows moderate to fresh northeast to east winds
within about 120 nm north of the frontal boundary and gentle
northeast to east winds elsewhere north of the boundary.
Scattered showers and isolated thunderstorms are within 60 nm
southeast of the cold front north of 27N. Isolated showers are
possible elsewhere near and along the frontal boundary. Seas are
mainly 3-6 ft west of the front. Northeast of the Lesser Antilles,
a trough extends from near 28N40W to 26N46W. Another trough
extends from near 29N45W to 25N54W and to 17N61W. A recent ASCAT
pass reveals generally light to gentle winds near these troughs.
Scattered moderate convection is seen from 29N to 30.5N and
between 43W-45W due to mainly an upper-level disturbance that
is riding northeastward along a jet stream branch located just
to the northwest of the second trough.

Farther east, a stationary front enters the discussion waters
from 31N26W to 28N29W, then transitions to a trough to near
27N31W. Winds west of the front and trough to 35W are moderate to
fresh in speeds along with 5-8 ft seas in a northwest to north
swell. Isolated showers are possible near and along the front
and trough. North of the ITCZ to 21N, the northeast to east
trades are moderate to fresh in speeds, with gentle to moderate
winds elsewhere. Seas are mainly 4-7 ft in mixed swell across the
remainder of the waters.

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. It is light elsewhere. 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, the stationary front will gradually
dissipate through Thu. High pressure in the wake of the front
will shift eastward across the western Atlantic along 31N- 32N
through Thu, producing moderate to fresh winds immediately north
of the front.

$$
Aguirre
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