[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 170552
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 UTC Fri Sep 17 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
0530 UTC.

...SPECIAL FEATURES...

Post-Tropical Cyclone Nicholas is centered near 30.7N 92.4W at
0300 UTC or 35 nm S of Alexandria Louisiana and moving N at 4 kt.
Estimated minimum central pressure is 1009 mb. Maximum sustained
wind speed is 15 kt with gusts to 25 kt. A surface trough extends
east-southeastward from Nicholas to the coastal waters just S of
SE Alabama-Florida Panhandle. Scattered showers and isolated
thunderstorms are seen across S Louisiana, central Mississippi
and Alabama, Florida Panhandle and the N central Gulf. Moderate to
locally fresh S winds and seas up to 4 ft are expected in the
Gulf near these thunderstorms. The convection associated with the
remnants of Nicholas will continue to affect these Gulf States
through Sun with up to 3 inches of rain possible. The Weather
Prediction Center is issuing bulletins on Nicholas and they can be
found at
http://www.wpc.ncep.noaa.gov/tropical/tropical_advisories.php?storm=NICHOLAS

A broad area of low pressure is located about 100 miles southeast
of the Outer Banks of North Carolina. Although the circulation of
this system has become a little better defined since yesterday,
the associated showers and thunderstorms remain disorganized and
located mainly well to the east of the center. Environmental
conditions are becoming more conducive for development, and a
tropical depression is likely to form during the next day or so
while the system moves northward to north-northeastward off the
southeast and mid-Atlantic U.S. coasts. Regardless of development,
this system could bring high surf to portions of the southeast
and mid-Atlantic U.S. coasts through this weekend. Additional
information on this system, including gale warnings, can be found
in High Seas Forecasts issued by the NOAA Ocean Prediction
Center. Please read the latest Tropical Weather Outlook at
www.hurricanes.gov for more details.

Showers and thunderstorms remain disorganized in association with
a tropical wave and broad area of low pressure located about 1100
miles west-southwest of the Cabo Verde Islands. However,
environmental conditions are expected to be conducive for
development during the next few days, and a tropical depression
could still form over the weekend. This system is expected to move
westward to west-northwestward at 15 to 20 mph across the
tropical Atlantic during the next several days and has a medium
chance of tropical cyclone formation in the next 48 hours. Please
read the latest Tropical Weather Outlook at www.hurricanes.gov for
more details.

...TROPICAL WAVES...

A tropical wave is near 15W from N Mauritania southward across
Senegal coast into the Atlantic Ocean, and moving W at 5 to 10
kt. Scattered moderate convection is found from 07N to 14N between
S Senegal/Guinea-Bissau and 19W.

An Atlantic tropical wave is along 40W from 17N southward and
moving W near 15 to 20 kt. A 1012 mb low near 09N39W is associated
with this wave. Scattered moderate convection is evident from 05N
to 17N between 37W and 45W. Latest scatterometer and altimetry
data show moderate to fresh with locally strong S to SE winds and
seas at 5 to 6 ft to the SE of the low. Refer to the Special
Features section above for more information on development
potential of this low.

A Caribbean tropical wave is near 82W from 19N southward to
central Panama, and moving west near 10 kt. Isolated
thunderstorms are found over the SW Caribbean Basin.

Another tropical wave is along 91W from near the Mexico-Guatemala
border southward into the E Pacific Ocean. Numerous heavy showers
and scattered thunderstorms are flaring up across the SE Bay of
Campeche, Guatemala and SE Mexico.

...MONSOON TROUGH/ITCZ...

A monsoon trough extends across the coast of Guinea-Bissau near
11N16W through a low near 11N20W to 07N45W. No ITCZ is found based
on the latest analysis. Scattered moderate to isolated strong
convection is present near the low from 10N to 13N between 19W and
24W. Scattered moderate convection is seen S of the monsoon trough
from 04N to 10N between 20W and 29W.

...GULF OF MEXICO...

For information on Post Tropical Cyclone Nicholas over SW Louisiana,
and associated convection in the Gulf, refer to the Special
Features section above.

Modest convergent SSE to SW winds are coupling with upper-level
winds shear to trigger scattered showers and isolated
thunderstorms over the E Gulf, including the Florida Keys and W
coast. Please read the Tropical Waves section for additional
convection in the Bay of Campeche. Moderate SE trades and seas of
3 to 5 ft are seen N of the Yucatan Peninsula and over the Yucatan
Channel. Otherwise, light to gentle variable winds and seas near 2
ft dominate the remainder basin.

For the forecast, Post-Tropical Cyclone Nicholas is drifting
northward away from the coast and into the interior of central
Louisiana, leaving a gentle winds and mostly slight seas across
the Gulf through the next several days.

...CARIBBEAN SEA...

Convergent trade winds are producing scattered showers and
isolated thunderstorms over W Hispaniola and adjacent waters.
Refer to the Tropical Waves section above for additional
convection across the Caribbean Basin. Moderate to fresh trades
and seas at 5 to 7 ft are present over the central and S central
basin. Gentle to moderate trades and seas of 2 to 4 ft prevail for
the rest of the basin.

For the forecast, the Atlantic ridge will build into the
Caribbean through late Sat, supporting fresh to strong winds over
the south-central Caribbean and over the Gulf of Honduras through
late Sat. The ridge will weaken starting Sun as an area of low
pressure currently well east of the area moves to the northeast of
the Leeward Islands early next week. There is a medium chance
this low pressure will form into a tropical cyclone over the next
couple of days. Regardless of further development, expect increase
winds, seas and thunderstorms east of the Leewards early next
week.

...ATLANTIC OCEAN...

Convergent fresh to strong S to SW winds feeding toward a low
pressure system off the S Carolina coast are generating numerous
heavy showers and isolated thunderstorms W of Bermuda, N of 30N
between 66W and 71W. Seas near this area range from 6 to 9 ft.
More information on this low can be found in the Special Features
section above. Enhanced by an upper-level trough in the vicinity,
a surface trough near 28N52W is causing scattered to numerous
moderate convection N of 27N between 45W and 53W. Another surface
trough farther SE near 24N44W is creating scattered moderate
convection from 24N to 27N between 42W and 46W. Convergent SW
winds near a surface trough across S Georgia are triggering
scattered showers and isolated thunderstorms off the N Florida-
Georgia coast. Refer to the Special Features, Tropical Waves and
Monsoon Trough/ITCZ sections for additional convection and sea
conditions across the Atlantic Basin.

The Atlantic ridge extending west-southwestward from the 1029 mb
Azores high, passing S of Bermuda to the Bahamas continues to
dominate the basin. Other than the areas related to the systems in
the Special Sections, light to gentle trades and seas at 4 to 5 ft
are seen N of 16N between 46W and the Florida coast and the
Greater Antilles; gentle to moderate SSE to SW winds and seas of 4
to 6 ft are present S of 13N between the African coast and the
Windward Island/S American coast. Moderate to locally fresh NE
trades and seas at 6 to 9 ft prevail elsewhere, including waters
near the Canary and Cabo Verde Islands.

For the forecast W of 45W, weak ridging across through the
central Bahamas will support mostly light breezes and slight seas
north of 22N through early next week, and moderate trade winds and
moderate seas south of 22N at least through Sat. Meanwhile, an
area of low pressure currently well to the southeast over the
tropical Atlantic will approach the waters northeast of the
Leeward Islands Sun and Mon. There is a medium chance this low
pressure will form into a tropical cyclone over the next couple of
days. Regardless of development, expect increased winds, seas,
and thunderstorms northeast of the Leeward Islands Sun into Mon.

$$

Chan
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