[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 110604
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 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 0000 UTC surface analysis and satellite imagery through
0600 UTC.

...SPECIAL FEATURES...

Hurricane Larry is centered near 48.7N 53.2W at 11/0600 UTC or
70 nm NNW of St. Johns Newfoundland moving NNE at 41 kt.
Estimated minimum central pressure is 963 mb. Maximum sustained
wind speed is 70 kt with gusts to 85 kt. Most of the convection is
over the northern semicircle. 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 be moving quickly away from
Newfoundland during the next several hours. Little change in
strength is forecast today, and Larry is expected to become a
strong extratropical low later this morning 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 tonight. 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 91W from the W 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. Upper-level
winds over the western Gulf of Mexico are expected to become more
conducive for development over the weekend, and a tropical
depression is likely to form on Sunday or Monday while the system
moves northwestward and then northward near the coast of
northeastern Mexico. Further development of this system will be
possible through the middle of next week if it remains over water,
and interests along the western and northwestern Gulf coast
should monitor the progress of this system. The chance of tropical
depression forming over the next 48 hours is high. Regardless of
development, this disturbance is expected to produce heavy rain
across portions of Central America and the Yucatan Peninsula
today, which may lead to flash flooding and mudslides. By late
this weekend, heavy rain will likely reach portions of the western
Gulf coast.

A strong tropical wave just off the coast of Africa, along 18W,
is moving W at 10-15 kt. Scattered moderate convection is observed
between Senegal and the Cabo Verde Islands. Environmental
conditions appear generally conducive for additional development,
and a tropical depression is likely to form late this weekend or
early next week while the system moves generally westward 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 its axis along 39W, south of 22N
and it is moving W at 15 kt. The wave is surrounded by dry and
dusty Saharan air, inhibiting the development of showers and
thunderstorms.

Another Atlantic tropical wave has is axis along 57W, south of
21N and it is moving W at 15 kt. Recent scatterometer satellite
data show a broad surface curvature, which is also evident on
satellite imagery. A few showers are noted near the northern part
of the wave between 55W and 61W.

A Caribbean tropical wave has its axis along 76W, south of 16N and
it is moving W at 10-15 kt. The interaction of this wave with the
E Pacific monsoon trough is enhancing scattered moderate to
isolated strong convection over N Colombia.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coast of Mauritania near
19N16W to 09N28W and to 07N40W. No ITCZ segment is identified.
Scattered moderate convection is noted south of the monsoon trough
from 03N to 09N and between 21W to 31W.

GULF OF MEXICO...

A complex weather pattern is allowing for a large area of
disorganized showers and thunderstorms across the S and SE Gulf of
Mexico, especially from SW Florida to the Bay of Campeche. The
strongest storms are actually inland over W Yucatan and SW Mexico.
The surface features found in the Gulf are a stationary front that
stretches across the N Gulf and a few showers are noted near this
boundary. Also, a sharp trough extends from the Bay of Campeche
near 18N94W to the NW Gulf near 27N94W.

A recent scatterometer satellite pass show fresh to locally strong
E-NE winds within 160 nm of the Yucatan peninsula, with the
strongest winds found in the E Bay of Campeche, S of 21N. Gentle
to moderate anticyclonic winds are found in the rest of the basin.
Seas of 2-4 ft are noted in the Bay of Campeche, SE and NW Gulf
waters, and 1-2 ft elsewhere in the Gulf.

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, a frontal boundary over the northern
Gulf will prevail through Sun supporting showers and thunderstorms
across the region.

CARIBBEAN SEA...

Please see the Special Features section above for details on the
tropical wave over Yucatan and Guatemala that is inducing
convection west of 85W.

Weakening evening storms are seen near the Tiburon peninsula of
Haiti and in the Windward Passage, and a few showers are seen off
the NW coast of Colombia and NE Panama. The rest of the Caribbean
Sea enjoys fairly tranquil weather conditions. A recent scatterometer
satellite pass show a large area of strong to locally near gale-
force trades in the south-central Caribbean, especially within
190 nm of the NW coast of Colombia and the Gulf of Venezuela. Seas
in the area are 6-9 ft. Moderate to fresh trades are noted in the
north-central and E Caribbean and the Bay of Honduras with seas of
4-6 ft. Gentle to moderate trades and seas of 2-4 ft are found
elsewhere in the basin.

For the forecast, the Atlantic ridge will continue to build westward
across the Caribbean, bringing an increase in the trade wind
flow this 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 through Sun. Scattered showers and
thunderstorms across the NW Caribbean are expected to reduce in
coverage by Sat.

ATLANTIC OCEAN...

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

A broad 1025 mb subtropical ridge is the dominant feature across
the tropical Atlantic. A cold front extends from a 1011 mb low
pressure near 35N68W to the Space Coast of Florida near Cape
Canaveral. A few showers are noted along this boundary. A surface
trough stretches from 16N49W to 1050W and scattered moderate
convection is observed from 13N to 17N and between 47N and 51W.
Satellite wind data show fresh to locally strong trades on the
northern portion of the trough from 14N to 18N and between 45W and
53W. Moderate to fresh NE winds are noted E of 35W, from 19N to
27N. Gentle to moderate easterlies prevail in the rest of the
basin. Seas of 4-7 ft is observed N of 14N and W of 35W, while
seas of 5-8 ft is seen E of 35W. Seas of 3-6 ft are found
elsewhere in the basin.

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 through early
next week. Otherwise, quiescent conditions will prevail through
midweek.

$$
DELGADO
This weather bulletin was brought to you by:
www.nashvilleweather.net