[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 102247
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Sat Sep 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 1800 UTC surface analysis and satellite imagery through
2230 UTC.

...SPECIAL FEATURES...

Hurricane Larry is centered near 43.5N 58.2W at 10/2100 UTC or
290 nm SW of Cape Race Newfoundland moving NNE at 30 kt.
Estimated minimum central pressure is 967 mb. Maximum sustained
wind speed is 70 kt with gusts to 85 kt. Numerous moderate with
embedded isolated strong convection extends outward for 360 nm
from the center, except to 120 nm in the SW quadrant. On the
forecast track, Larry will move over southeastern Newfoundland
tonight. Little change in strength is expected before landfall in
Newfoundland. After landfall, Larry should weaken and become an
extratropical cyclone on Saturday before it merges with another
low over the Labrador Sea on Sunday. Swells generated by Larry
will affect Bermuda, the east coast of the United States, and
Atlantic Canada through Saturday night. These swells are likely to
cause life-threatening surf and rip current conditions. 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 NHC
Forecast/Advisory and Public Advisory at www.hurricanes.gov for
more details.

A tropical wave extends along 90W from the northwest Yucatan
Peninsula southward through Guatemala. This is southeast of a
broad upper trough reaching from the lower Mississippi Valley to
the western Bay of Campeche. The interaction of tropical wave with
divergent flow aloft on the southeast side of the upper trough is
supporting large clusters of showers and thunderstorms across the
south-central Gulf of Mexico and northwest Caribbean Sea. The
northern part of the tropical wave is forecast to move into the
Bay of Campeche and merge with a pre- existing surface trough by
Sunday. Environmental conditions are expected to be conducive to
support gradual development thereafter, and a tropical depression
is likely to form on Sunday or Monday before the system moves
onshore along the western Gulf of Mexico coast. The chance of
tropical depression forming over the next 48 hours is medium.
Regardless of development, this disturbance is expected to produce
heavy rains across portions of Central America and the Yucatan
Peninsula through Saturday. Heavy rains are likely to reach
portions of the western Gulf coast late this weekend.

A strong tropical wave over the far eastern Atlantic along 15N, moving
W at 10-15 kt. Scattered moderate convection is observed from
03N-08N between 20W-23W. A tropical depression is likely to form late
this weekend or early next week as the system moves west-
northwestward over the far eastern Atlantic near the Cabo Verde
Islands. Interests in the Cabo Verde Islands should monitor the
progress of this system. The disturbance has a medium chance of
development over the next 48 hours.

...TROPICAL WAVES...

An Atlantic tropical wave has an axis along 37W from 06N-22N,
moving W at 15 kt. No significant convection is evident near this
tropical wave.

An Atlantic tropical wave has an axis along 55W from 05N-22N,
moving W at 10-15 kt. No significant convection is noted with
the wave at this time.

A Caribbean tropical wave has an axis along 74W from 13N
southward to central Colombia, moving W at 10-15 kt. No
significant convection is noted with this wave at this time.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coast of Mauritania near
19N16W to 09N30W to a 1012 mb low pressure near 13N48W. Scattered
moderate convection is ongoing within 120 nm north of this low
pressure.

GULF OF MEXICO...

A stationary front reaches from near Crystal River, Florida to
Brownsville, Texas. A few showers and thunderstorms are active
along the front west of 90W. A sharp surface trough extends from
Tabasco Mexico near 18N92.5W to just southeast of Brownsville.
Scattered to numerous showers and thunderstorms are active mainly
south of 25N between 82W-92W. Coastal observations confirm fresh
NE to E winds off the Texas coast north of the front, with 2 to 4
ft seas. Fresh NW winds are active off Veracruz, west of the sharp
surface trough, confirmed by 20 kt winds at Coatzacoalcos. Sea are
also 2 to 4 ft in this area. Light breezes and slight seas are
noted elsewhere.

For the forecast, see the Special Features section above for
information on the tropical wave that has potential to develop
into a tropical cyclone over the southwest Gulf of Mexico Sunday
or Monday. Elsewhere, the frontal boundary over the northern Gulf
will remain nearly stationary through Sunday, bringing showers and
thunderstorms across the region.

CARIBBEAN SEA...

Please see the Special Features section above for details on the
tropical wave over Central America that is inducing convection
west of 80W.

A few showers and thunderstorms are active over off western Cuba
in the northwest Caribbean, as well as in the far southwest
Caribbean, near the monsoon trough which reaches from central
Colombia to central Panama. Thunderstorms are active over the
highlands of Hispaniola as well. No other significant shower or
thunderstorm activity is evident. Fresh to strong trade winds and
6 to 8 ft seas are noted over the south-central Caribbean.
Moderate to fresh trade winds and 4 to 6 ft seas are noted
elsewhere, except for gentle to moderate SE winds and 2 to 5 ft
seas over the northwest Caribbean.

For the forecast, the Atlantic ridge will continue to build
westward across the Caribbean, bringing an increase in the trade
wind flow through the weekend. Fresh to strong winds will occur
offshore Colombia and in the Gulf of Venezuela, mainly at night
through Sun. Fresh to strong winds are also likely in the late
evening in the Gulf of Honduras starting on Sat. Scattered showers
and thunderstorms are expected to continue across the NW
Caribbean today and reduce in coverage by Sat.

ATLANTIC OCEAN...

Please see the Special Features section above for details on
Hurricane Larry over the NW Atlantic.

A cold front reaches from 32N71W to near Daytona Beach, Florida. A
few showers and thunderstorms are noted along this boundary west
of 77W. A 1009 mb low pressure, the remnants of Tropical
Depression Mindy, is near 34N70W. Fresh winds and seas to 8 ft are
evident north of 28N between 67W-72W, south of this feature. The
Atlantic ridge extends from 1024 mb high pressure near 34N46W
through the central Bahamas, supporting light to gentle breezes
and mainly 4 to 6 ft seas elsewhere west of 65W. Farther east
gentle to moderate trade winds and mostly 4 to 6 ft persist south
of the ridge. The exceptions are fresh winds and seas to 7 ft
within 180 nm north of 1012 mb low pressure near 13N48W, and fresh
to strong NE winds with 6 to 9 ft seas from 20N to the Canary
Islands and east of 23N to the coast of Africa.

For the forecast over the western Atlantic west of 65W, swells
generated by Hurricane Larry will also subside by tonight. A
frontal boundary will linger across the area through Sun which
will bring showers and thunderstorms across the area during the
weekend.

$$
Christensen
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