[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111036
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 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 0600 UTC surface analysis and satellite imagery through
1000 UTC.

...SPECIAL FEATURES...

Hurricane Larry is centered near 50.7N 51.7W at 11/0900 UTC or
250 nm NNE of Cape Race Newfoundland moving NNE at 42 kt.
Estimated minimum central pressure is 966 mb. Maximum sustained
wind speed is 65 kt with gusts to 80 kt. Most of the convection
is over the northern semicircle with numerous moderate to
isolated strong convection extending outward for 300 nm from the
center. On the forecast track, Larry will continue to quickly move
north-northeast today. Larry is forecast to transition into a
post-tropical cyclone later today, and merge with a larger
non-tropical low by tonight. Significant swells from Larry will
continue affecting 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. Disorganized showers and
thunderstorms over portions of Central America, southeastern
Mexico, and the adjacent waters of the northwestern Caribbean Sea
and southern Gulf of Mexico are associated with this tropical
wave interacting with an upper-level trough. 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. 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, including coastal Texas and Louisiana through the
middle of next week. Localized significant rainfall amounts will
be possible, resulting in limited flash and urban flooding. This
system has a high chance of formation in the next 48 hours.

A tropical wave with an axis along 19W is producing a
concentrated area of showers and thunderstorms 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 an axis along 19W from 20N
southward, moving W at 10-15 kt. Scattered moderate convection is
noted from 12N to 16N between 17W and 23W. See the Special
Features section for more information on this wave.

An Atlantic tropical wave has an axis along 40W from 23N
southward, moving W at 15 kt. The wave is surrounded by dry and
dusty Saharan air which is inhibiting the development of
convection.

An Atlantic tropical wave has an axis along 59W from 22N
southward, moving W at 15 kt. Satellite imagery shows broad
surface curvature with this wave. Scattered moderate convection
is noted from 16N to 21N between 56W and 62W.

A Caribbean tropical wave has an axis along 77W from 16N
southward, moving W at 10 kt. The interaction with this wave and
the E Pacific monsoon trough is enhancing scattered moderate to
isolated strong convection over the SW Caribbean.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coast of Mauritania near
19N16W to 11N28W to 06N34W. The ITCZ continues from 06N34W to
08N40W. Aside from the convection noted in the tropical waves
section, scattered moderate convection is noted from 03N to 09N
between 23W and 37W.

GULF OF MEXICO...

A complex weather pattern is allowing for a large area of
disorganized showers and thunderstorms across the southern Gulf
of Mexico, especially in the Bay of Campeche. A surface trough
extends across the Bay of Campeche from 25N95W to 19N93W.
Scattered moderate convection is noted S of 26N between 90W and
98W. In the northern Gulf of Mexico, a stationary front continues
to linger from north of Tampa Bay, Florida near 28N93W to 28N94W.
Scattered showers and thunderstorms are within 100 nm of the
front. Overnight 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 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. Expect an increase in winds and seas along these
regions with this system. Meanwhile, 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.

Scattered moderate to isolated strong convection is noted along
the monsoon trough and tropical wave in the SW Caribbean S of 14N
between 75W and 83W. Elsewhere, a complex of thunderstorms are
moving near the Cayman Islands. Isolated thunderstorms continue to
move across the waters near Hispaniola and Puerto Rico. Overnight
scatterometer data depicted 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 later today.

ATLANTIC OCEAN...

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

A cold front extends across the SW N Atlc from 31N69W to 29N76W
with the rest of front stalled from 29N76W to the central Florida
coast near 28N81W. Scattered showers and thunderstorms are noted
within 80 nm of the front. A trough extends across the southern
Bahamas from 25N73W to 20N73W. Isolated thunderstorms are north of
Hispaniola and Puerto Rico from 19N to 22N between 66W and 71W.
Otherwise, high pressure extends across the tropical Atlantic
anchored by a 1025 mb high near 36N47W. A surface trough is
analyzed from 17N50W to 09N51W with scattered moderate convection
from 13N to 16N between 48W and 55W. Overnight scatterometer data
depicted 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 subside this morning. A frontal
boundary will linger across the area through Mon which will bring
showers and thunderstorms across the area through early next week.
Otherwise, quiescent conditions will prevail through Tue.

$$
AReinhart
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