[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 101209
TWDAT

Tropical Weather Discussion...Updated
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.

Updated 1210 UTC for Special Features...

...SPECIAL FEATURES...

Hurricane Larry is centered near 39.2N 60.8W at 10/1200 UTC or
565 nm SW of Cape Race, Newfoundland 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 240 nm of the center in the
southern semicircle and 210 nm in the northern semicircle. On
the forecast track, Larry is expected to turn to the northeast
with a further increase in forward speed 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 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
conducive to support gradual development, and a tropical
depression is likely to form Sunday or Monday before the system
moves onshore along the western Gulf of Mexico coast. The chance
of tropical cyclone formation within the next 48 hours is
medium. Regardless of development, this disturbance is expected
to produce heavy rains across portions of Central America
through Saturday.

A strong tropical wave is expected to emerge off of the west
coast of Africa by tonight. Environmental conditions are
forecast to be conducive for gradual development thereafter, 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. 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.

...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.

$$
Hagen/AReinhart
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