[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 101040
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Fri Sep 10 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
1030 UTC.

...SPECIAL FEATURES...

Hurricane Larry is centered near 37.7N 61.8W at 10/0900 UTC or
360 nm NNE of Bermuda moving NNE at 23 kt. Estimated minimum
central pressure is 968 mb. Maximum sustained wind speed is 75
kt with gusts to 90 kt. Numerous moderate to strong convection is
noted within 250 nm of the center in the southern semicircle and
200 nm in the northern semicircle. On the forecast track, Larry
is expected to turn to the northeast with a further increase in
forward speed is expected today. The center of Larry will pass
well southeast of Nova Scotia today, and move over southeastern
Newfoundland tonight. Gradual weakening is forecast during the
next day or so, but Larry is expected to remain a hurricane until
it passes Newfoundland. Larry should become an extratropical
cyclone on Saturday, and is now forecast to be absorbed by a
larger extratropical low near Greenland by the end of the weekend.
Swells generated by Larry will continue to affect the Bahamas
today. Significant swells from Larry will continue affecting
Bermuda, the east coast of the United States, and Atlantic Canada
through Saturday. 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 strong tropical wave is expected to emerge off of the west coast
of Africa later today or tonight. Environmental conditions are
forecast to be conducive for development thereafter, and a
tropical depression is likely to form by 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 and a high
chance of development over the next 5 days. Please see the latest
Tropical Weather Outlook from the National Hurricane Center.

...TROPICAL WAVES...

An Atlantic tropical wave has an axis along 35W south of 21N,
moving W at 15-20 kt. No significant convection is noted with this
wave at this time.

An Atlantic tropical wave has an axis along 49W south of 21N,
moving W at 10-15 kt. No significant convection is noted with this
wave at this time.

A Caribbean tropical wave has an axis long 72W from 18N southward,
moving W at 10-15 kt. This wave has isolated thunderstorms within
60 nm of the axis especially near the Hispaniola coast.

A Caribbean tropical wave has an axis along 88W from 20N
southward, moving W around 10 kt. Scattered moderate to isolated
strong convection is noted in the Gulf of Honduras and the NW
Caribbean from 13N to 21N between 82W and 88W. This system is
forecast to move into the Bay of Campeche and merge with a pre-
existing surface trough located over the southwestern Gulf of
Mexico by this weekend. Environmental conditions are expected to
be conducive to support gradual development, and a tropical
depression could form Sunday or Monday before the system moves
onshore along the western Gulf of Mexico coast. For more details,
please read the latest Tropical Weather Outlook from the National
Hurricane Center.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the Guinea-Bissau cost near
12N16W to 06N23W to 10N42W. No ITCZ segment is analyzed. Scattered
moderate to isolated strong convection is noted along and south of
the monsoon trough from 03N to 11N between 11W and 24W. Isolated
thunderstorms are also noted from 03N to 07N between 29W and 33W.

...GULF OF MEXICO...

At 0900 UTC, a cold front extended off of the Florida Big Bend
near 30N83W to the Middle Texas coast near 28N96W. Isolated
showers and thunderstorms are noted within 90 nm of the front.
Moderate north-northeast winds are north of the front with light
to gentle winds elsewhere across the basin. A trough extends
across the western Gulf from 27N95W to 19N93W. Scattered moderate
to isolated strong convection is noted near and east of this
trough from 18N to 26N between 85W to 97W. Thunderstorms are also
occurring on the bay side of the Florida Keys. Seas are 1 to 3 ft
across the Gulf.

For the forecast, the northern portion of a tropical wave is producing
disorganized showers and thunderstorms over the NW Caribbean.
This system is forecast to move into the Bay of Campeche and merge
with a pre- existing surface trough located over the southwestern
Gulf of Mexico by this weekend. Environmental conditions are
expected to be conducive to support gradual development, and a
tropical depression could form Sunday or Monday before the system
moves onshore along the western Gulf of Mexico coast. This system
has a low chance of development in 48 hours and medium chance in
the next 5 days. Regardless of development, this system could
bring an increase in winds and seas across the Gulf waters during
the upcoming weekend. Meanwhile, a frontal boundary over the
northern Gulf will continue through Sun will bring showers and
thunderstorms across the region.

...CARIBBEAN SEA...

Please see the Tropical Waves section for details on the tropical
waves moving across the area.

Outside of the convection associated with the tropical wave near
the Gulf of Honduras, most of the Caribbean Sea is dominated by
dry weather conditions. Scattered thunderstorms are noted in the
SW Caribbean near the monsoon trough, S of 12N between 77W and
83W. Overnight scatterometer satellite pass depict strong to
locally near gale- force trades in the south- central Caribbean,
especially within 150 nm of the NW coast of Colombia. Moderate to
fresh trades are found in the north- central Caribbean, E
Caribbean and NW Caribbean, while gentle to moderate trades are
noted in the SW Caribbean. Seas of 6-9 ft are prevalent in the
south-central Caribbean and 3-6 ft elsewhere in the basin.

For the forecast, the Atlantic ridge will build westward across
the Caribbean Sea 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 Sat
night. Fresh to strong winds are also likely in the late evening
in the Gulf of Honduras Friday and Saturday. 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.

Scattered moderate convection is occurring in the SW N Atlantic
ahead of a sinking cold front, N of 26N between 71W and 79W.
Otherwise, the 1024 mb subtropical ridge is beginning to re-
assert dominance over the tropical Atlantic as Hurricane Larry
continues to move away.

Fresh to strong cyclonic winds associated with the circulations of
Post-Tropical Cyclone Mindy are noted north of 29N between 71W
and 75W. Seas in this area are 8-11 ft. Winds in the wake of Larry
are moderate to locally fresh with seas to 10 ft. Larger swells
traveling farther away from Larry are generating seas of 5-8 ft N
of 23N between 69W and the Florida- Georgia coast, including the
Bahamas. Otherwise, high pressure dominates the central and
eastern Atlantic. A tight pressure gradient over the NE Atlantic
results in fresh to strong NE winds within 180 nm of the coasts of
Morocco and Western Sahara, and the waters surrounding the Canary
Islands. Seas in this region are 7-10 ft. Gentle to moderate
easterlies prevail across the rest of the basin with seas of 4-7
ft.

For the forecast, fresh to strong winds from Post-Tropical
Cyclone Mindy are expected to move north of the forecast waters by
this morning. Seas associated with Mindy will subside by tonight.
Swells generated by Hurricane Larry will also subside by tonight.
A frontal boundary will linger across the SW N Atlantic through
Sun which will bring showers and thunderstorms across the area
during the weekend.

$$
AReinhart
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