NHC Atlantic Tropical Weather Discussion


000
AXNT20 KNHC 200003
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Sat Nov 20 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.

...SPECIAL FEATURES...

Gulf of Mexico Gale Warning: As of 21Z, a cold front extends
from near St. Petersburg, Florida southwest to 27N87W, where it
becomes stationary to 24N95W and to inland Mexico near
Coatzacoalcos. Minimal northwest to north gale-force winds
are confined to the far SW Gulf south of 21N and west of 95W,
with seas of 10-13 ft. These conditions will continue through
tonight, with little change in the sea heights. The front will
dissipate this weekend leading to improving marine conditions.
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 over Africa. The ITCZ begins near
05N13W to 06N30W to just east of a trough near 08N42W. It
resumes west of the trough near 08N45W to the coast of French
Guiana near 05N53W. The trough is along a position from
10N42W to 05N46W. A second trough is north of the ITCZ along
a position from 14N30W to 07N36W. Scattered moderate to strong
convection is along the ITCZ and second surface trough from 04N
to 14N between 32W and 38W. Scattered moderate to isolated
strong convection is seen from 04N to 12N between 23W-29W.
Scattered moderate convection is within 60 nm of the ITCZ
between 16W-19W.

GULF OF MEXICO...

Please see the Special Features section above for details on a
Gale Warning that is currently in effect for a section of
the SW Gulf.

As of 21Z, a cold front extends from near St. Petersburg,
Florida southwest to 27N87W, where it becomes stationary to
24N95W and to inland Mexico near Coatzacoalcos. Satellite
imagery shows areas of rain, with embedded scattered showers
and isolated thunderstorms south of 23N and between the front
and 90W. Areas of rain with possible embedded scattered showers
are noted from 24N to 25N west of 90W. The latest scatterometer
data depicts fresh to strong north to northeast winds north of
the front, with moderate to fresh north to northeast winds south
of the front. Seas in the western Gulf are 3-6 ft, with higher
seas to about 12 ft near the gale force winds. Seas are 1-3 ft
in the eastern Gulf. Strong high pressure is quickly building
behind the front attendant by dry atmospheric conditions.

For the forecast, the aforementioned cold front will dissipate
this weekend allowing for marine conditions to improve, however,
the respite will be short-lived as another cold front will move
over the NW Gulf early on Mon, and move south of the basin Tue.
Fresh to strong northerly winds are expected behind the front.
Strong high pressure will build across the Gulf region in the
wake of this next cold front.

CARIBBEAN SEA...

Satellite imagery shows scattered showers and isolated
thunderstorms over the section of the western Caribbean
that confined from 14N to 17N and west of 80W to inland
southern Honduras and northern Nicaragua. Upper-level
disturbances riding northeastward along a subtropical
jet stream branch that stretches from the eastern Pacific
to across the northern Yucatan Peninsula and to the southeastern
Gulf of Mexico are helping to maintain this activity rather
active. Isolated small showers moving westward in the trade
wind flow are noted elsewhere north of 15N and west of 71W.

The latest scatterometer data depicts moderate to fresh winds
across the central Caribbean. Gentle to moderate winds are noted
in the eastern portions of the basin and light to gentle winds in
the NW Caribbean. Seas in the 3-5 ft range are noted across the
basin. Seas to 6 ft are over the area from 11N to 15N between
72W-85W.

For the forecast high pressure north of the area will shift
eastward in response to a cold front that is east of northeastern
Florida. Winds and seas will further diminish early next week,
ahead of a stronger cold front that will move across the Gulf
of Mexico Mon. This cold front will reach from the Yucatan
Channel by late Mon night, and extend from eastern Cuba to the
Gulf of Honduras by late Tue. Fresh to locally strong winds and
building seas are expected in the wake of the front.

ATLANTIC OCEAN...

As of 21Z, a cold front that recently has moved over the
northwest part of the area extends from near 31N76W southwestward
to inland central Florida near Cape Canaveral. Fresh northeast
winds are behind the front. Also as of 21Z, a trough is to east
and southeast of South Florida along a position from near 27N76W
to inland central Cuba near 23N80W. Latest scatterometer data
indicated fresh northeast to east winds near the northern part
of this trough. Seas with these winds are in the 4-6 ft range.
Areas of rain along with scattered showers and thunderstorms are
seen east and northeast of this trough from 25N to 28N between
72W and 80W.

In the central Atlantic, a shear line stretches off the tail-end
of a stationary front from near 31N37W to 24N50W and to near
22N62W. Scattered showers and a few thunderstorms are observed
within 180 nm north of the shear line between 48W-53W, and
within 30 nm south of the shear line between 44W-49W. This
activity is quickly moving west-southwest. Farther east, a
1011 mb low is analyzed near 26N33W, with a trough southwestward
to 22N36W and to near 20N44W. Another trough extends from the
low to near 26N26W. Satellite imagery shows scattered moderate to
isolated strong convection within 120 nm north of the second
trough. This activity is being aided by an upper- level shortwave
trough. Gentle to moderate cyclonic winds are around the low,
with light to gentle winds south of 22N. A trough is also
analyzed east of the Lesser Antilles along 60W from 10N to 20N.
No significant convection is occurring with this feature as it is
under dry sinking air.

Northerly swell, generated by a strong low pressure system
located north of the area, will reach the forecast waters late
on Sat, building seas to 10-14 ft roughly north of about 29N and
between 25W-40W by Sun morning.

The Cumbre Vieja volcano, on the island of La Palma in the Canary
Islands, has been active for two months(since 19 September 2021).
An ash emission is ongoing. Medium ash concentration is noted in
the vicinity of the volcano, low 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 aforementioned cold front will
stall across the northern forecast waters this weekend, before
lifting back north ahead of a stronger cold front that will move
off the northeast Florida coast Mon. Before this occurs, strong
high pressure will build 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 over these waters through the weekend as the
seas will increase as well. The second cold front will reach
from Bermuda to eastern Cuba Tue. Fresh to strong northerly winds
and building seas are expected behind this front.

$$
Aguirre
Source: nhc.noaa.gov

NHC Atlantic Tropical Weather Discussion