[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111757
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Thu Nov 11 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
1630 UTC.

...SPECIAL FEATURES...

Showers and thunderstorms associated with a storm-force non-
tropical area of low pressure located more than 1000 miles ENE of
Bermuda have changed little in organization since last night.
Although there is still a small chance the system could become a
short-lived subtropical storm today, the system is quickly moving
over cooler waters and the likelihood of subtropical development
has decreased. Therefore, the chance of development has decreased
to low. Additional information on this system, including hurricane-
force wind warnings, can be found in High Seas forecasts issued by
the National Weather Service at website -
ocean.weather.gov/shtml/NFDHSFAT1.php

...MONSOON TROUGH/ITCZ...

A monsoon trough exits the African coast near the Guinea-Sierra
Leone border at 09N13W through a 1011 mb low near 07N16W to
07N21W, then continues as an ITCZ to 08N40W to 07N56W; just N of
Suriname. Numerous moderate to isolated strong convection is
noted near the low and part of the ITCZ from 02N to 10N between
the African coast and 26W. Scattered moderate convection is seen
farther W near the ITCZ from 06N to 09N between 27W and 35W, and
from 05N to 09N between 48W and the Suriname-French Guiana
border.

The E Pacific monsoon trough is causing scattered showers near
Costa Rica, Panama and nearby Caribbean waters.

...GULF OF MEXICO...

An outflow boundary is triggering scattered showers and
thunderstorms over the NW corner of the Gulf, S of Galveston,
Texas. Fresh with locally strong winds with seas up to 6 ft are
expected near this boundary. Otherwise, a broad surface ridge is
supporting light to gentle ESE to SSW winds and seas at 2 to 4 ft
across much of the Gulf.

On the forecast, a cold front will move into the N Gulf coastal
waters tonight, move southward across the Gulf Fri then stall and
dissipate across the Yucatan Channel Sat. A reinforcing front
will follow closely behind the first front, entering the N Gulf
Fri night, then move southeastward across the Gulf through Sun.
Looking ahead, high pressure building across the N Gulf on Sun
will strengthen into Mon, supporting fresh winds over the SE and
S central Gulf.

...CARIBBEAN SEA...

A surface trough is coupling with divergent winds aloft to trigger
scattered showers and thunderstorms across the W basin, including
W Cuba. The western end of a shear line is producing similar
conditions over the N coast of central Cuba. Refer to the Monsoon
Trough/ITCZ section for additional weather in the basin. Recent
satellite scatterometer and altimetery data indicate moderate to
fresh easterly trades and seas of 5 to 6 ft over the S central and
NW basin. NE to E gentle to moderate trades with seas at 2 to 4
ft prevail for the rest of the basin.

For the forecast, the shear line over N Cuba will be dissipating
through tonight. Afterward, a cold front will stall over the
Yucatan Channel Sat, then dissipate. A slight stronger front will
move into the NW Gulf Sun then stall from E Cuba to the Gulf of
Honduras. Looking ahead, this second front will shift eastward
into the Windward Passage through Mon as reinforcing high pressure
builds N of the area behind a third front moving through the W
Atlantic. This pattern will support fresh NE winds across parts of
the NW Caribbean Mon and Mon night.

...ATLANTIC OCEAN...

A weakening cold front curves southwestward from the N central
Atlantic across 31N44W to near 24N58W, then continues westward as
a shear line across the SE Bahamas to the N coast of central Cuba.
Scattered showers and isolated thunderstorms are occurring up to
80 nm on both sides of this boundary between 31N44W and 22N72W,
and also from the N coast of Cuba northward to the NW Bahamas. An
upper-level trough near 24N20W is generating scattered showers
along the Guinea-Bissau/Senegal/Mauritania coast and adjacent
waters. Refer to the Monsoon Trough/ITCZ section of additional
convection in the basin.

N to ENE gentle to moderate with locally fresh winds and seas of 7
to 10 ft are present near and N of the cold front/shear line,
between 46W and the Florida coast/Bahamas. Moderate to fresh NE
trades and seas at 5 to 7 ft are found near the Canary Islands
from 23N to 28N between the NW African coast and 21W. A 1018 mb
high over the central Atlantic is promoting light to gentle winds
and seas of 4 to 5 ft N of 20N between 21W and 46W. Gentle to
moderate NNE to ENE trades with seas at 4 to 5 ft are present
from 08N to 20N between the African coast and Lesser Antilles.
Gentle to moderate with locally fresh E to SE trades and seas of 4
to 6 ft prevail for the remainder of the basin.

For the forecast west of 65W, high pressure between Bermuda and
NE Florida will shift east today ahead of a cold front that will
move off the NE Florida coast by early Fri. The front will stall
and weaken from roughly 31N72W to central Cuba by early Sat.
Afterward, a second front will move off the NE Florida coast
later on Sat, then merge with the first front before stalling from
roughly Bermuda to central Cuba Sun. Looking ahead, a third,
stronger front will move off the NE Florida coast late Sun night,
eventually overtaking the aforementioned stalled front, and then
reach from 27N65W to the Windward Passage by late Mon.

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 latest Volcanic Ash Advisory issued by
Meteo-France at website http://vaac.meteo.fr/volcanoes/la-palma/.

$$

Chan
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