[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181759
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Sat Sep 18 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 1200 UTC surface analysis and satellite imagery through
1755 UTC.

...SPECIAL FEATURES...

Tropical Storm Odette is centered near 38.5N 67.3W at 18/1500 UTC
or 205 nm SE of Nantucket Massachusetts moving NE at 15 kt.
Estimated minimum central pressure is 1002 mb. Maximum sustained
wind speed is 40 kt with gusts to 50 kt. Seas are peaking at 12 to
13 ft near and up to 90 nm in a semicircle N of the center.
Odette remains highly sheared, with an exposed and elongated
center. Numerous moderate to isolated strong convection is noted
well NE of the center from 35N to 41N and between 58W and 64W.
A turn toward the east-northeast at a faster forward speed is
expected by this evening. Odette should then slow down and turn
toward the east and southeast on Monday and Tuesday. On the
forecast track, the center of Odette will pass south of Atlantic
Canada Sunday and Monday. Strengthening is forecast during the
next day or two, and Odette is expected to become a strong post-
tropical low by tonight. Please read the latest NHC Public
Advisory at https://www.nhc.noaa.gov/text/MIATCPAT5.shtml for more
information. The Atlantic Offshore Waters Forecast issued by OPC
can be found at
https://www.ocean.weather.gov/offshore/indexphp?basin=atl&type=offshore#close

Atlantic Gale Warning: An Atlantic tropical wave has its axis
along 51W, south of 21N, and a 1008 mb low pressure near 15N51W.
The disturbance is producing a large area of showers and
thunderstorms, especially over the northern semicircle, from 14N
to 20N and between 48W and 54W. Recent satellite-derived wind data
indicate that strong to near gale-force E winds are occurring over
the NE quadrant, mainly between 15N and 18N and between 48W and
52W. The disturbance is producing seas of 7-10 ft. Only a slight
increase in organization of this system would lead to the
formation of a tropical depression or tropical storm, which is
expected to occur later today or tonight while the low moves
toward the west-northwest at about 15 mph. This system is expected
to be near the northern Leeward Islands on Monday and Tuesday,
and interests there should monitor its progress. Upper-level winds
are likely to become less conducive for development when the
system reaches the southwestern Atlantic by the early to middle
part of next week. Regardless of development, increased winds,
seas, and convection is likely within 120 to 180 nm mainly on the
north side of the low over the next couple of days. Refer to the
latest NHC Tropical Weather Outlook at www.hurricanes.gov for more
details.

Another Atlantic tropical wave has its axis along 26W, south of
19N, and a 1008 mb low pressure near 09N26W. The interaction
between the disturbance and the monsoon trough results in a large
area of showers and thunderstorms extending from 03N to 15N and
between 20W and 37W. Recent satellite-derived wind data show
fresh to strong cyclonic winds on the southern semicircle from 02N
to 11N and between 20W and 35W. Environmental conditions appear
conducive for further development of this system, and a tropical
depression could form over the next couple of days while moving
toward the northwest at 10 to 15 mph to the west of the Cabo Verde
Islands. This system is expected to reach cooler waters and an
area of stronger upper-level winds early next week, which could
limit its development. Refer to the latest NHC Tropical Weather
Outlook at www.hurricanes.gov for more details.

...TROPICAL WAVES...

A tropical wave has its axis along 89W, south of 19N, extending
from the peninsula of Yucatan, across Guatemala and W El Salvador,
and into the E Pacific Ocean. The wave is moving W at 10 kt. No
deep convection is occurring in association with this tropical
wave.

...MONSOON TROUGH/ITCZ...

A monsoon trough extends across the coast the Mauritania at
18N16W through the 1008 mb low mentioned in the Tropical Waves
section near 09N26W to 06N37W. The ITCZ then continues from 0638W
to 10N46W and then from 10N54W to the coast of Guyana near
08N59W. The shower and thunderstorm activity noted is associated
with the tropical disturbances between Africa and the Lesser
Antilles. Refer to the Special Section for more details.

...GULF OF MEXICO...

A surface trough is analyzed from the coast of Louisiana near
30N91W to near the coast of NE Tamaulipas near 25N97W. Another
surface trough is noted in the SW Gulf of Mexico from 18N94W to
24N95W. A combination of these features and upper level divergence
due to a short-wave trough is allowing for scattered moderate
convection from the central Bay of Campeche to the N Gulf coast,
between 86W to 95W. Recent satellite-derived wind data show fresh
to strong winds N 28N and between 88W and 92W, in association with
the convection in the area. Moderate to locally fresh SE winds
are observed in the south-central Gulf and in the E Bay of
Campeche, with gentle to moderate anticyclonic winds elsewhere in
the basin. Seas are 1-3 ft in the Gulf.

For the forecast, weak high pressure will extend across the
eastern and central Gulf of Mexico through early next week. This
pattern will support continued gentle to moderate winds and mostly
slight seas across the Gulf through the next several days.
Looking ahead, a weak cold front may move into the northwest and
north-central Gulf by mid week.

...CARIBBEAN SEA...

The eastern extension of the E Pacific monsoon trough enters the
SW Caribbean Sea near the Costa Rica and Panama border and
continues to NW Colombia. A few showers are noted near the coast
of NE Panama. The rest of the basin is dominated by generally dry
weather conditions, suppressing the development of showers and
thunderstorms. A recent scatterometer satellite pass show fresh to
strong trades in the south-central Caribbean Sea, with the
strongest winds occurring within 110 nm of the coast of NW
Colombia. Seas in the area are 7-10 ft. Moderate to fresh trades
are observed in the north-central Caribbean, with the strongest
winds occurring in the Windward Passage. Seas in this region are
4-7 ft. Moderate to fresh trades are also seen in the Gulf of
Honduras, with gentle to moderate trades elsewhere in the basin,
and seas of 3-6 ft.

For the forecast, the Atlantic ridge will shift westward through Sun,
as Tropical Storm Odette, off the middle Atlantic coast, lifts
northward. This will support fresh to strong winds over the
south-central Caribbean and Gulf of Honduras into early Sun. The
ridge will weaken starting Sun night as a tropical wave and area
of low pressure currently across the central Atlantic along 52W move
to the northeast of the Leeward Islands early Mon, then begin to
move more NW. There is a high chance this low pressure will form
into a tropical cyclone over the next several days. Regardless of
further development, expect increase winds, seas and thunderstorms
north through east of the Leewards early next week.

...ATLANTIC OCEAN...

Please see the Special Features for the information on the two
disturbances in the tropical Atlantic with a chance of tropical
development over the next few days.

A broad 1029 mb subtropical ridge anchored near the Azores extends
southwestward to the Bahamas and Florida. A weak surface trough is
analyzed along 51W from 22N to 29N and it is only producing a few
shallow showers near the trough axis. A few showers are also noted
off the NE coast of Florida in association with convection
spilling from the Gulf of Mexico. The rest of the basin enjoys
fairly tranquil weather conditions. Fresh to locally strong NE
winds are observed off the coast of NW Africa and the waters
surrounding the Canary Islands. Fresh to strong winds are noted
in recent satellite-derived wind data off the NE coast of South
America with the strongest winds occurring within 140 nm of NE
Brazil. Gentle to moderate anticyclonic winds in the rest of the
basin. Seas in the tropical Atlantic are 3-6 ft.

For the forecast west of 65W, weak ridging through the northern
Bahamas will support mostly light breezes and slight seas north
of 22N through early next week, and moderate to fresh trade winds
and moderate seas south of 22N at least through Sun. Meanwhile, an
area of low pressure currently well to the southeast over the
central tropical Atlantic along 52W will approach the waters
northeast of the Leeward Islands Sun and Mon then begin to move
more NW over open Atlantic waters. There is a high chance this low
pressure will form into a tropical cyclone over the next several
days. Regardless of further development, expect increase winds,
seas and thunderstorms north through east of the Leewards Islands
and northeast of Puerto Rico early next week.

$$
DELGADO
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