[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211058
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Thu Sep 21 2023

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 0600| UTC surface analysis and satellite imagery through
1045 UTC.

...SPECIAL FEATURES...

Hurricane Nigel is centered near 40.6N 47.8W at 21/0900 UTC or
430 nm SE of Cape Race Newfoundland, moving NE at 26 kt. Estimated
minimum central pressure is 977 mb. Maximum sustained wind speed
is 75 kt with gusts to 90 kt. Peak seas related to Nigel are
presently to 42 ft. Satellite imagery depicts the cyclone not in
as good as shape as it was several hours ago. Upper-level
vertical wind shear has begun to impinge on Nigel. The earlier
large eye feature is now obscured. Deep convection of numerous
moderate to strong type intensity has become displaced to the
north and northeast of Nigel from 20N to 43W between 48W-50W and
from 42N to 43W between 45W-48W. The convection is being
stretched northeastward by the wind shear. Numerous moderate to
strong convection is within 120 nm southwest through of Nigel.
Nigel is forecast to maintain its present motion for the next day
or two. Weakening is forecast during the next couple of days, and
Nigel is forecast to become a post-tropical cyclone by Fri.
Swells generated by Nigel currently affecting Bermuda will
gradually subside through to tonight. These swells are likely to
cause life- threatening surf and rip current conditions. Please
consult products from your local weather office. Please read the
latest HIGH SEAS FORECAST issued by the National Hurricane Center
at website - https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the
latest Nigel NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

Atlantic Gale Warning: The pressure gradient between low
pressure that is expected to develop along a stationary front
N of the Bahamas and high pressure over the southeastern U.S.
will result in frequent north to northeast wind gusts to 35 kt N
of 30N and W of 75W beginning by early this evening, then north of
30N and between 76W-78W late tonight into early on Fri. Seas with
these winds are forecast to be 8-12 ft, but may reach higher
values as the north to northeast winds counter act the Gulf
Stream current. Please see the latest NWS High Seas Forecast
issued by the National Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2 for further details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 23W from
04N to 20N, including the Cabo Verde Islands. It is moving
westward at 5 to 10 kt. A large cold overcast with embedded
numerous moderate to strong convection is west of the wave
from 11N to 16N between 25W-29W.

A central Atlantic tropical wave has its axis along 38W from
04N to 19N. It is moving westward around 15 kt. Scattered
moderate to isolated strong convection is east of the wave
from 05N to 09N. Scattered moderate convection is within
120 nm west of the wave from 07N to 13N.

A western Atlantic tropical wave has its axis along 53W south of
16N, moving westward at about 10 kt. No significant convection is
occurring with this tropical wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends off the coast of Senegal near
16N17W and continues southwestward to 10N30W and westward to
11N45W and to 10N52W. The ITCZ axis extends from 10N52W to
10N60W. Nearby significant convection is discussed in the TROPICAL
WAVES section above.

...GULF OF MEXICO...

A slowly dissipating stationary front extends from near Sarasota,
Florida to 28N86W. Scattered showers and a few thunderstorms
are over the eastern Gulf waters from 25N to 28N between 83W-86W.
Isolated showers are elsewhere east of 87W. Moderate to fresh
east to southeast winds are in the NE Gulf per latest ASCAT data
over that part of the Gulf. A weak surface trough is noted in the
eastern Bay of Campeche, with moderate to fresh northeast
winds near it. Only isolated showers are possible near this
trough. Seas of 2-4 ft are across the basin.

For the forecast, high pressure will be in control of the
weather pattern across the Gulf waters allowing for generally
gentle to moderate east to southeast winds and slight seas, except
pulsing to moderate to fresh offshore the western Yucatan
Peninsula in the evenings. Developing low pressure east of Florida
will tighten the pressure gradient over the NE Gulf bringing
moderate to locally fresh NE winds across the NE Gulf tonight into
Fri. A frontal trough associated with the aforementioned low
pressure will move across the southeastern Gulf and the Straits of
Florida Thu night into Fri.

...CARIBBEAN SEA...

A persistent deep-layer trough that stretches from the western
Atlantic to east-central Cuba and 13N83W is helping to sustain an
area of scattered showers and thunderstorms south of Cuba from
17N to 21N between 75W-81W and in the southwestern Caribbean south
of 15N and west of 77W. A weak pressure gradient is allowing for
moderate to fresh easterly trade winds in the central Caribbean.
Fresh to strong northeast to east winds are again present just off
the N Colombia and NW Venezuelan coasts. Seas in the central
Caribbean are in the range of 4-7 ft. Elsewhere, gentle to
moderate winds and seas of 3-5 ft continue.

For the forecast, long period north to northeast swell moving
through the Tropical N Atlantic waters and Caribbean passages will
subside Thu. Moderate to fresh trade winds in the central
Caribbean will change little through the next few days. Northeast
to east trade winds will pulse to fresh to strong speeds offshore
northern Colombia and northwest Venezuela during the afternoons
and at night into early next week.

...ATLANTIC OCEAN...

Please read the SPECIAL FEATURES section for details on Hurricane
Nigel and on an Atlantic Gale Warning. In addition, please read
the TROPICAL WAVES and MONSOON TROUGH/ITCZ sections for details
on convection in the Atlantic Ocean.

A stationary front extends from just south of Bermuda to 29N73W
and to inland Florida just south of Daytona Beach, Florida. The
combination of this front and a very sharp upper-level trough
over its vicinity is leading to numerous moderate to strong
convection from 24N to 31N between 71.5W and 74W and west of 79W.
A surface trough extends from near 29N73W to just east of the
central Bahamas. It is helping to contribute additional scattered
showers and thunderstorms to the waters north and northeast
of the Bahamas. Moderate to fresh northeast to east winds are
north of the front per latest ASCAT data passes.

Farther east, another trough extends from near 31N55W to 24N58W.
Only small isolated showers and thunderstorms are near this
trough. Otherwise, weak high pressure ridging is the main
feature controlling the weather pattern west of 50W. An area
of scattered showers and thunderstorms is noted from m near
19N48W. Moderate to fresh trades are evident from 18N to 23N
between 43W-54W. This activity is being sustained by an elongated
upper-level low that is centered near 18N52W. The low is moving
westward as depicted in water vapor imagery.

Moderate to fresh trade winds are evident from 17N-27N between
the coast of Africa and 55W between broad high pressure north of
that area and three tropical waves to the south along the monsoon
trough/ITCZ. Locally strong winds are occurring off the coast of
Western Sahara. Seas in the broad zone of trade winds are 7-9 ft.
Across the remainder of the basin, gentle to moderate winds and
4-7 ft seas remain, except for higher seas of 6-8 ft in northwest
to north swell over the waters north of 29N between 49W-56W. This
swell was generated by Hurricane Nigel.

For the forecast W of 55W, the aforementioned stationary front
will lift northward on Fri as low pressure develops along it to
the east of northern Florida, and where frequent gusts to gale
force are possible tonight  into Fri. This non-tropical low
pressure system could acquire some subtropical characteristics on
Fri while it moves generally northward. In its wake, high pressure
ridging will build from E to W just north of the forecast waters
into early next week.

$$
Aguirre
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