[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 190000
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Fri Nov 19 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
2315 UTC.

...SPECIAL FEATURES...

Gulf of Mexico Gale Warning: Gale-force northwest to north winds
will develop offshore of Veracruz Fri afternoon as strong high
pressure builds in behind a cold front that is presently over
the NW Gulf and that will reach the southeastern Gulf this
weekend, becoming stationary from near Naples, Florida to the
Bay of Campeche. Peak seas will reach to near 12 ft with the
gale-force winds. Conditions are forecast to diminish to below
gale-force late Fri night as the high pressure shifts eastward
allowing for the culprit gradient to slacken. Please see the
latest NWS High Seas Forecast issued by the National Hurricane
Center at website://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for
more information.

...MONSOON TROUGH/ITCZ...

The monsoon trough remains mostly confined to the African
continent. It reaches the Atlantic through the coast of Sierra
Leone near 08N13W and extends to 07N14W, where latest
scatterometer data indicates that it transitions to the ITCZ
to 05N21W to 07N29W and to 06N39W. A surface trough is just west
of the ITCZ along a position from near 10N37W to 04N41W.
Scattered moderate to isolated strong convection is within 180 nm
north of the ITCZ between 25W-29W and within 180 nm south of the
ITCZ between 30W-39W. Scattered moderate convection is within 60
nm of the surface trough from 05N to 08N.

GULF OF MEXICO...

Please see the Special Features section above for details on a
Gale Warning that is in effect for waters near Veracruz, Mexico.

As of 2100 UTC, a cold front extends from south-central
Louisiana to inland northeastern Mexico. A trough out ahead of
the front extends from 29N88W to 26N91W. Numerous thunderstorms,
with frequent lightning are along and within 60 nm east of the
trough from 27N to 29N, and also within 60 nm east of the trough
from 26N to 27N. Another trough is analyzed from near 25N88W to
inland the western Yucatan Peninsula. Isolated showers are
possible near the northern part of this trough.

Deep atmospheric moisture and divergence aloft occurring east of
a mid to upper-level disturbance is confined to the
southeastern. These factors are significantly contributing to
widespread moderate to isolated strong convection south of 26N
and east of 86W, including the Straits of Florida. Latest
scatterometer data depicts fresh to strong mainly east winds near
and around this convective activity. Otherwise, gentle to
moderate winds are present ahead of the front and trough.
Observed seas are in the 3-5 ft range in the southeastern Gulf,
4-6 ft in the central Gulf and 2-4 ft elsewhere.

For the forecast, the aforementioned cold front will continue to
move across the northern and western Gulf through Fri, reaching
gale force off Veracruz, Mexico. The front will stall from near
Naples, Florida, to the Bay of Campeche this weekend, before
dissipating. Looking ahead, another front will move into the
northwest Gulf early Mon, and reach from southwest Florida to
the southwest Gulf by late Mon night.

CARIBBEAN SEA...

Scattered moderate convection is within 30 nm of line from
14N80W to 14N84W. Isolated showers and thunderstorms are
elsewhere west of about 79W. Elsewhere, water vapor imagery
depicts moderate to strong subsidence and dry sinking air across
the basin. This is suppressing the atmospheric moisture over
just about the entire basin and inhibiting convective activity
from developing.

The pressure gradient between the strong subtropical ridge near
Bermuda and lower pressures across northern South America is
inducing fresh to strong northeast to trades across most of the
central and southwestern Caribbean. The latest ASCAT pass
revealed that the strongest winds are present to the south of
Hispaniola. Elsewhere, winds are mainly in the moderate to fresh
range. Seas of 6-8 ft in the fresh to strong trades south of
11N and between 72W-80W, with lower seas of 5-7 ft in the
eastern Caribbean and 4-6 ft elsewhere.

For the forecast, the fresh to locally strong northeast winds
persist in a broad swath from the northeast Caribbean into the
southwest Caribbean. Winds and seas will diminish through Fri as
high pressure north of the area shifts east, ahead of a cold
front moving into the Gulf of Mexico and western Atlantic. Winds
will diminish and seas will subside early next week, ahead of a
stronger cold front that will move over the Gulf Mon. This
stronger front will reach the Yucatan Channel by late Mon night
and extend from eastern Cuba to the Gulf of Honduras by late Tue.

ATLANTIC OCEAN...

A cold front enters the tropical Atlantic near 31N42W to 28N48W,
where it begins to dissipate to 25N54W, then transitions to
a shear line westward to 23N61W and to 23N75W. No convection is
associated with this boundary. Fresh to strong northeast to east
winds are north of the cold front and shear line extending to
30N. These winds are resulting in a rough sea state, with seas of
8-10 ft. Latest scatterometer data indicates that fresh
northeast to east winds, along with seas up to 7 ft, are south
of the front and west of about 50W.

Satellite imagery shows a large area of scattered showers and
thunderstorms over the far western Atlantic from the NW Bahamas
to 28N, while areas of rain with embedded scattered showers and
thunderstorms are from 28N to 32N and west of 73W. This activity
is being aided by mid to upper-level disturbances that are moving
north and northeastward within the strong upper-level flow
pattern that is present from the Yucatan Peninsula to the western
Atlantic. Indications from model guidance are that this activity
will remain fairly active into Sat. Mariners can expect strong
gusty winds and reduced visibility in heavy rain produced by the
showers and thunderstorms.

Farther east, earlier scatterometer data imagery revealed that a
rather weak trough extends from near 26N31W to 20N34W and to
18N43W, and is surrounded by gentle winds. No significant
precipitation is associated with this feature. North of this
trough, an area of moderate to fresh east winds is north of 28N
and between 25W-40W. Seas of 6-8 ft prevail in the central and E
tropical Atlantic. Moderate or weaker winds and fairly tranquil
weather conditions are present elsewhere.

The Cumbre Vieja volcano, on the island of La Palma in the
Canary Islands, has been erupting since 19 September 2021.
Recent camera observations indicate that volcanic ash extends
up to 12,000 ft, but the extent of its coverage is difficult
to determine as it is being obscured by clouds. 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, The shear line will dissipate tonight in
advance of a cold front that will move off the northeast
Florida coast Fri. The front will become stationary roughly
along 28N this weekend, before lifting north ahead of a strong
cold front that will move off the northeast Florida coast late
Mon. Before then, strong east winds are expected to develop over
most of the western Atlantic north of the front as strong high
pressure builds over the eastern United States. Marine conditions
are expected to become hazardous over those waters as seas will
build to around 11 ft with these winds. The second cold front
will reach from Bermuda to eastern Cuba by Tue evening.

$$
Aguirre
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