[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210002
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Sun Nov 21 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 1800 UTC surface analysis and satellite imagery through
2345 UTC.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coastal plains of Guinea
near 11N15W and continues to 07N21W, where latest scatterometer
data indicates that it transitions to the ITCZ continuing to
07N29W to 04N35W and to 04N46W. Scattered moderate convection is
seen from 01N to 07N between 20W-29W, from 07N to 14N between
26W-32W and within 120 nm north of the ITCZ between 32W-35W.

GULF OF MEXICO...

As of 21Z, a cold front is analyzed from near Fort Myers, Florida
to 24N86W, where it becomes a trough to inland the western
section of the Yucatan Peninsula and continues to southeastern
Mexico to the northern sections of the Isthmus of Tehuantepec.
Satellite imagery shows broken to overcast multilayer clouds,
with scattered showers and thunderstorms along and to between
60-90 nm northwest of the trough. Isolated showers and
thunderstorms are southeast of the trough. Elsewhere to the
northwest of the front and trough, strong subsidence aloft as
noted in water vapor imagery, is inhibiting convection from
developing there. At the surface, a ridge extends from western
Louisiana to the interior of Mexico, where high pressure of 1023
mb is analyzed near 22N102W.

Latest ASCAT data shows moderate to fresh northeast to east winds
over the eastern and central Gulf, while gentle to moderate
east-southeast winds are over the western half of the Gulf.
Seas are in the 5-7 ft range over the NE Gulf, 4-6 ft over the
central Gulf, 6-9 ft over the SW Gulf due to a northeast swell
and lower seas of 2-4 ft over the NW Gulf.

As for the forecast, the aforementioned front will gradually
dissipate tonight and Sun as high pressure builds across the
region. A strong cold strong will make its way into the basin by
early Mon. Fresh to strong northerly wind will be expected
behind the front, mainly over the eastern Gulf, Mon through Tue
night. High pressure is forecast to build in behind the front
by middle of the upcoming week.

CARIBBEAN SEA...

A surface trough is analyzed along 64W from 15N to 19N. The
eastern segment of the E Pacific monsoon trough reaches from
northern Panama to inland the northwest coast of Colombia near
11N74W. Latest ASCAT data indicates a northeast to southeast
wind shift across the axis. These winds are of gentle to moderate
speeds. No convection is noted with this trough as it remains
under subsidence aloft that is allowing for very dry and stable
atmospheric conditions to exist over the eastern and central
section of the basin. Isolated showers moving quickly westward
are possible north of 14N between 63W and 67W, and between 76W-
80W. In contrast to the eastern and central Caribbean sections,
deep atmospheric moisture aided by a subtropical jet stream
branch covers just about the entire western half of the basin.
Scattered showers and a few thunderstorms are noted south of 16N
between 80W and the coast of Central America. Small isolated
showers are north of 16N and west of 80W.

The latest scatterometer data shows moderate to fresh trades
south of about 16N and between 71W and 80W. The data also shows
gentle to moderate trades elsewhere over the remainder of the
sea, except for mainly gentle winds over the western section
of the sea and near the Windward Passage. Seas are in the
3-5 ft range, except for slightly lower seas of 2-4 ft north
of 15N and between 64W and 85W.

As for the forecast, mainly gentle to moderate trades will
prevail across much of the Caribbean Sea through Sun night.
A cold front is forecast to reach the Yucatan Channel by Mon
evening, and extend from eastern Cuba to the Gulf of Honduras by
Tue evening. Fresh to locally strong winds and building seas are
expected behind the front across the western Caribbean, the
Windward Passage and Mona Passage.

ATLANTIC OCEAN...

A cold front stretches from just east of Bermuda southwestward
to 31N67W and to 28N75W, where it becomes weaker to inland South
Florida near West Palm Beach and southwest from there to near
Fort Myers. Fresh to strong northeast to east winds are north
of this front. A surface trough is over the Bahamas along 78W.
It reaches south to the coast of Cuba. Ample deep atmospheric
moisture acted upon by jet stream energy from a subtropical jet
stream branch that extends from the southeastern Gulf of Mexico
northeastward to east of northern Florida is resulting in
numerous to scattered showers and isolated thunderstorms south
of the cold front and west of 65W. Some of this activity may
contain strong gusty winds and heavy rain that can reduce
visibility.

Over the eastern part of the area, a broad upper-level trough
is located north of about 19N and between 20W and 50W, This
feature is sustaining a cold front that extends from a 1001 mb
low that is north of the area near 36N33W, southwestward to
31N29N and to 24N37W, where it begins to dissipate to near
21N49W. Satellite imagery reveals isolated showers along and near
this front. Latest scatterometer data passes show moderate to
fresh northwest to north winds behind the front east of 40W, and
mainly moderate northeast to east winds elsewhere behind the
front. Moderate winds or lighter are elsewhere over the area.
Seas are in the 7-11 ft range behind both fronts, mainly due to
swell, and 4-7 ft elsewhere, except for seas of 6-8 ft due to a
north to northeast swell from 22N to 27N between 70W and the
Bahamas.

The Cumbre Vieja volcano, on the island of La Palma in the
Canary Islands, has been erupting since 19 September 2021.
Medium ash is in the vicinity of the volcano, while low
concentration is 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 W of 65W, the weakening aforementioned
cold front will stall and remain across the northern forecast
waters through Sun night, before lifting north ahead of a
strong cold front that will move off the northeast Florida coast
on Mon. Before this occurs, strong high pressure is building
offshore the southeastern United States creating a tight
pressure gradient over the western part of the area. This is
expected to lead to strong northeast to east winds over a large
oceanic fetch area resulting in hazardous marine conditions
through late Sun, with large swells possibly lingering into
Mon.

$$
Aguirre
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