[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171741
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Wed Nov 17 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 1200 UTC surface analysis and satellite imagery through
1700 UTC.

...MONSOON TROUGH/ITCZ...

The monsoon trough reaches the Atlantic through the coast of
Guinea-Bissau near 11N16W to 08N18W. The ITCZ extends from 08N18W
to 06N23W to 07N32W, then resumes west of a surface trough from
05N37W to 04N45W. The surface trough extends from 10N34W to
04N36W. Scattered moderate convection is noted within 60 nm of the
ITCZ between 19W to 22W. Scattered moderate convection is also
noted north of the ITCZ to 10N between 25W to 29W. Additional
areas of scattered moderate convection surround the surface trough
from 01N to 07N between 30N to 40W.

GULF OF MEXICO...

High pressure has moved well east of the area into the Atlantic
and moderate southerly return flow is setting up in advance of
the next cold front. Southerly return flow is locally fresh along
the Texas coast. Seas are mainly 3 to 5 ft. Fresh to strong east
winds are over the southeastern Gulf and Straits of Florida with
seas 4 to 7 ft. Deep tropical moisture moving in from the
northwest Caribbean is allowing for scattered showers and
thunderstorms embedded within these easterly winds.

For the forecast, fresh E winds in the southeast Gulf will
gradually diminish tonight as a cold front moves into the NW Gulf
Thu. This front will move SE of the basin Fri night. Fresh to
strong northerly winds and building seas will follow the front,
with winds to gale force possible off Veracruz Fri. Scattered
showers and isolated thunderstorms are expected ahead of this
front. Looking ahead, another front may move off the Texas coast
late Sun night.

CARIBBEAN SEA...

A surface trough extends from central Cuba to 18N83W. Another
surface trough is noted just offshore Belize and Yucatan coast.
These boundaries combined with deep tropical moisture and upper-
level divergence are producing numerous moderate to isolated
strong convection N of 20N, W of 83W. Another area of similar
convection is noted from 17N to 19N between 82W to 85W. The rest
of the Caribbean is dry, except for scattered moderate convection
noted just off the coasts of Nicaragua, Costa Rica, and northern
Panama, in association with localized land breezes as well as the
eastern extension of the Pacific monsoon trough along 10N.

High pressure N of the Greater Antilles and lower pressure across
South America is translating to a tight pressure gradient over
the basin, and thus fresh winds encompass most of the basin. A
scatterometer satellite pass revealed strong winds occurring
offshore Colombia and adjacent portions of the south central
Caribbean, including offshore of southern Hispaniola. Seas of 8 to
10 ft are occurring in the area of higher winds offshore Colombia,
with 5 to 7 ft seas across the rest of the basin, except 4 to 6
ft in the NW.

For the forecast, showers and thunderstorms over the NW Caribbean
will decrease in areal coverage on Thu. High pressure will
strengthen and build south through the basin. Combined with lower
pressure over South America, the pressure gradient will tighten,
allowing strong winds over portions of the central Carribbean and
passages of the Greater Antilles into Thu. A cold front is
forecast to approach the Yucatan Channel by Fri night.

ATLANTIC OCEAN...

A cold front enters the tropical Atlantic near 31N54W and extends
to 26N67W, where it transitions to a surface trough that
continues across the central Bahamas and into central Cuba. No
significant convection is occurring along this boundary. Fresh to
locally strong winds are occurring within about 210 nm N of the
boundary, especially just E of the central and NW Bahamas.

Farther east, a 1014 mb low pressure is near 27N30W. A weakening
surface trough associated with the low pressure extends from
27N28W to 20N32W to 18N40W. An additional trough is noted in a
scatterometer satellite pass extending WSW from the low to 24N41W.
Scattered moderate convection is noted N of 25N and between 25W
and 31W. Fresh to locally strong mainly easterly winds are noted N
of the low between 20W and 40W.

Aside from the winds near the cold front and low pressure, to the
W of 40W, mainly moderate winds prevail except fresh winds north
of the Lesser Antilles to 22N. Gentle to moderate winds are
occurring elsewhere. Seas across the basin are broadly 5 to 9 ft,
highest S of 15N, near the low pressure, and behind the cold
front N of 29N.

The Cumbre Vieja volcano, on the island of La Palma in the
Canary Islands, has been erupting since 19 September 2021.
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 cold front that currently extends from
31N54W to 26N67W will reach from 31N36W to 24N56W by Fri morning,
with strong NE winds following the front. Farther west, the
surface trough reaching from 26N67W to central Cuba will dissipate
late today or tonight as high pressure builds over the western
Atlantic. This will lead to increasing E winds and building seas
south of 28N tonight through Thu night. Looking ahead, a cold
front will move offshore northeast Florida by Fri, then stall from
Bermuda to central Cuba over the weekend. This front will be
followed by fresh to strong northeast to east winds and building
seas north and northeast of the Bahamas.

$$
Mora
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