[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 190002
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Wed Nov 18 2020

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 32N. 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: Strong autumn high pressure will
continue to build southward across the Gulf of Mexico behind a
stationary front that extends from western Cuba to the northern
Yucatan Channel and to the northern Yucatan Peninsula. The high
pressure will continue to create a very tight gradient between it
and the front leading to strong northeast winds, with frequent
gusts to gale force over the southeastern half of the Gulf
waters, including the Straits of Florida and the waters adjacent
to the Yucatan Channel through early Thu- 19/1200 UTC. Expect
building seas of 10-16 ft across this area. Very hazardous
conditions can be expected between the wind waves against the
flow of the Gulf stream through the Straits of Florida, and due
to a southeast swell propagating through the Yucatan Channel.
Please read the latest NWS High Seas Forecast issued by the
National Hurricane Center at website
https://www.nhc.noaa.gov/text/ MIAHSFAT2.shtml for more details.

Caribbean Gale Warning: The same conditions that are occurring in
the southeastern half of the Gulf of Mexico behind a stationary
front that stretches from western Cuba across the northern
Yucatan Channel and to the northern Yucatan Peninsula will
support support strong winds, frequent gusts to gale
force, and large seas over the far northwestern Caribbean through
tonight. Large and hazardous seas of 8-13 ft will be present
in the Gulf of Honduras and the Yucatan Channel as fresh
northerly wind waves behind the front mix with east-southeast
swell. The highest seas are expected in the Yucatan Channel.
Please read the latest NWS High Seas Forecast issued by the
National Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details.

Atlantic Gale Warning: The pressure gradient which will lead to
frequent gusts to gale force over the southeastern Gulf of Mexico
and far northwestern Caribbean Sea will also bring frequent gusts
to the western Atlantic off the coast of South Florida and the
Bahamas behind the cold front that extends from near 32N59W to
36N70W and to western Cuba near 23N81W, where it becomes
stationary from there to across the northern Yucatan Channel
and to the northern Yucatan Peninsula. These gusts will begin
this evening-19/0000 UTC and continue through Thu evening-
20/0000 UTC offshore the Bahamas from 22N to 27N and west
of 61W. Expect wave heights to build to 9-14 ft with the highest
of the wave heights in the gulf stream, then northeast of the
Bahamas by Thu night. Please read the latest NWS High Seas
Forecast issued by the National Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details.

...TROPICAL WAVES...

A central Atlantic low-amplitude tropical wave has its axis
extending from near 15N41W to 08N43W and to 02N44W. It is
moving westward at 15-20 kt. Scattered moderate to isolated
strong convection is within 240 nm west and 180 nm east of
the wave from 05N to 09N.

An eastern Caribbean Sea tropical wave has its axis along 63W
south of 19N to well inland eastern Venezuela. It is moving
westward at 10-15 kt. Scattered showers and isolated
thunderstorms are within 30 to 60 nm either side of the wave from
14N to 16N.

A central Caribbean Sea tropical wave has its axis extending from
Haiti near 19N73W southward to inland northwestern Colombia.
Scattered moderate convection is within 120 nm east of the wave
from 15N to 18N.

...MONSOON TROUGH/ITCZ

The monsoon trough axis extends from the coast of Sierra Leone
near 08N12W to 06N18W, where latest scatterometer data indicates
that it transitions to the ITCZ to 06N26W to 04N33W and to just
west of a tropical wave near 04N41W. It resumes at 03N44W to just
inland the coast of Brazil near 01N51W. Scattered moderate to
isolated strong convection is within 150 nm north of the ITCZ
between 33W-40W. Scattered moderate convection is within 60 nm of
the ITCZ between 20W-33W and within 60 nm north of the ITCZ
between 48W-50W.

Scattered moderate to isolated strong convection is north and
northwest of the ITCZ from 04N to 09N between 48W and the coast
of South America.

GULF OF MEXICO...

See Special Feature section above for details on a Gale Warning
in effect over the southeastern half of the Gulf of Mexico.

A stationary front extends from western Cuba across the northern
Yucatan Channel and to the northern Yucatan Peninsula. Scattered
showers and isolated thunderstorms are along and to within
120 nm south of the front. Strong high pressure is over the area,
with a very tight gradient between it and the front. As a result,
strong winds, frequent gusts to gale force, and building wave
heights to 12 or 13 ft can be expected through tonight across
the central Gulf and Straits of Florida as high pressure builds
north of the area behind a front stalling across the Yucatan
Channel. Winds and seas will diminish through late Sat across the
basin. Looking ahead, a weak cold front will move into the
northwest Gulf and stall late Sun through Mon.

CARIBBEAN SEA...

Please see the Special Features section for information on
a Gale Warning in effect for the northwestern Caribbean north of
20N.

A stationary front extends from  western Cuba across the
northern Yucatan Channel and to the northern Yucatan Peninsula.
South of this front, fresh to strong northeast winds are
present over the northwestern Caribbean, with wave heights of
8-12 ft due to a tight pressure gradient from strong high
pressure over the Gulf of Mexico that is building behind and
across the front. The remnant low of Iota has moved west of El
Salvador and into the eastern Pacific Ocean near 14N91W. Remnant
moisture from this low is contributing to scattered shower and
thunderstorm activity over most of the western Caribbean, with
the additional support of a 1011 mb low centered on the eastern
edge of the Pacific monsoon trough axis near 13N81W. This low is
part of a broad area of low pressure that is situated over the
southwestern Caribbean. Scattered moderate to strong convection
is noted from 11N to 14N between 77W-80W. Scattered moderate to
isolated strong convection is within 120 nm of the 1011 mb low in
the SE and S quadrants. Isolated showers and thunderstorms are
elsewhere west of 80W and south of 16N between 75W-80W. Scattered
showers and isolated thunderstorms are over the central
Caribbean from 15N to 18N between 66W-70W. Isolated showers and
thunderstorms are south of 15N between 66W-70W.

Mainly moderate trades are elsewhere over the Caribbean, with
wave heights in the range of 4-6 ft, except for higher wave
heights in the 6-8 ft in the central Caribbean.

With regards to the aforementioned 1011 mb low near 13N81W,
development, if any, of this system is expected to slow to occur
during the next several days while it drifts west-southwestward
or westward across the southwestern Caribbean Sea. Regardless of
tropical cyclone formation, areas of heavy rain are possible
during the next several days from Nicaragua southward across
Central America and into Colombia. These rains could cause new
flooding concerns, especially across previously inundated areas.
Please read the latest Tropical Weather Outlook issued by the
National Hurricane Center at website
www.nhc.noaa.gov/text/MIATWOAT.shtml for more details.

ATLANTIC OCEAN...

See the Special Features section for details on a Gale Warning in
effect for a portion of the SW N Atlantic.

A cold front extends from near 32N59W to 36N70W and to western
Cuba near 23N81W, where it becomes stationary from there to
across the northern Yucatan Channel. A trough is analyzed
southeast of this front from near 31N58W to 23N65W, while an
upper-level trough axis extends from near 32N67W southwestward
to 26N71W and to near 23N78W. Plenty of atmospheric instability
along with the additional factor of the dynamics from a
rather vigorous jet stream branch that is riding east-
northeastward along the upper trough axis is all combining
and leading to a 60 nm wide line of scattered moderate to
isolated strong convection from 32N56W to 27N62W, and also within
30 nm of a line from 27N62W to 24N65W. Another cold front is
just northwest of the area along a position from 32N69W to
31N76W. Otherwise, high pressure is present over the remainder of
the area.

Moderate to fresh northeast winds are west of 65W along with
seas of 7-11 ft outside the gale warning area. Moderate to fresh
northeast to east winds are east of 65W, with the exception of
gentle to moderate winds between 60W-65W. Seas are 5-8 ft across
the remainder of the basin in mixed swell.

The cold front that extends from near 32N59W to 36N70W and to
western Cuba near 23N81W will stall from near 26N65W to central
Cuba by late Thu, then lift northward and diminish through Fri.
High pressure north of the area will support fresh to strong NE-E
winds across most the region through Fri, with frequent gusts to
gale force are forecast from 22N to 27N tonight through Thu
night. Looking ahead, a trough will form east of the Bahamas
starting Fri night, and may become a weak low pressure area
between the northern Bahamas and Bermuda by early next week.

A non-tropical area of low pressure could form between the
Bahamas and Bermuda by early next week. This system could
gradually develop subtropical characteristics through the middle
of next week while it moves northeastward. Please read the
latest Tropical Weather Outlook issued by the National Hurricane
Center at website www.nhc.noaa.gov/text/MIATWOAT.shtml for more
details.

$$
Aguirre
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