[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 110024
TWDAT

Tropical Weather Discussion...UPDATED
NWS National Hurricane Center Miami FL
0025 UTC Sat Sep 11 2021

Updated the Special Features to include the 11/0000 UTC information
on Hurricane Larry and disturbances

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 44.9N 56.5W at 11/0000 UTC or 205
nm SW of Cape Race Newfoundland moving NNE at 30 kt.
Estimated minimum central pressure is 958 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,
the center of Larry will pass well southeast of Nova Scotia today,
and 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
early 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 for
gradual development over the weekend, and a tropical depression is
likely to form on Sunday or Monday before the system moves near or
onshore of 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 just off the coast of Africa, along 15W, is
moving W at 10-15 kt. Scattered moderate convection is observed from
03N-08N between 20W-23W. Environmental conditions appear generally
conducive for additional development and 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/Delgado
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