[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 141215
TWDAT

Tropical Weather Discussion...Updated
NWS National Hurricane Center Miami FL
1205 UTC Tue Sep 14 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.

Updated 1215 UTC for Special Features...

Based on 0600 UTC surface analysis and satellite imagery through
1120 UTC.

...SPECIAL FEATURES...

At 14/1200 UTC, Tropical Storm Nicholas is inland over Texas near
29.5N 95.5W, or about 15 nm SSW of Houston, moving NNE at 7 kt.
Estimated minimum central pressure is 999 mb. Maximum sustained
wind speed is 50 kt with gusts to 60 kt. Peak seas in the NW Gulf
are 22 ft as of 14/0600 UTC. Numerous moderate and isolated strong
convection is noted within 180 nm NE and 120 nm in the SE
quadrant. Scattered moderate convection is noted along an outer
band further southeast from the center north of 25N extending W of
90W to Matamoros, Mexico. On the forecast track, the storm should
move more slowly to the northeast later today and then eastward
by Wednesday over Louisiana. Little motion is anticipated on
Thursday. Nicholas should weaken further today and is forecast to
become a tropical depression by Wednesday morning. Nicholas is
expected to produce heavy rain and flooding from the upper Texas
coastal areas across central to southern Louisiana into
Wednesday. Please read the latest High Sea Forecast issued by the
National Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest
Nicholas NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

A tropical wave located just west of the African coast is
producing a large area of showers and thunderstorms that are
showing signs of organization. The tropical wave axis is along
18W with a 1008 mb low pressure near 12N18W. A large cluster of
moderate to strong convection covers the area from 04N-17N between
15W-23W. Environmental conditions are conducive for a tropical
depression to form during the next couple of days while the system
moves generally westward at 15 kt across the eastern tropical
Atlantic. This system has a high chance of tropical cyclone
formation within 48 hours. Please, see the latest Tropical
Weather Outlook at www.hurricanes.gov for more details.

...TROPICAL WAVES...

A tropical wave is in the Atlantic Ocean along 38W from 1N
southward, moving W at around 15 kt. Scattered moderate
convection is noted on either side of the wave axis from 09N-14N
between 37W-41W.

A tropical wave over the Caribbean Sea with its axis along 62W.
Scattered showers with embedded thunderstorms are seen ahead of
the wave axis over the eastern Caribbean, particularly from
14N-18N between 60W-67W. The wave combined with an upper-level
low spinning over Hispaniola will support showers and
thunderstorms over the U.S. Virgin Islands, Puerto Rico and
Hispaniola tonight and Wed.

Another tropical wave is in the Caribbean Sea along 77W, and
extends from eastern Cuba to northern Colombia. Isolated to
scattered moderate convection is observed near the wave axis but
mainly over northern Colombia, and near Cabo Cruz, Cuba.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from 12N16W to 10N30W to 07N43W. The
ITCZ continues from 07N43W to the coast of Guyana near 06N58W.
Scattered moderate convection is seen south of Sierra Leone and
Liberia, and from 03N-09N between 21W-29W.

...GULF OF MEXICO...

Attention remains focused on Tropical Storm Nicholas. Refer to
the Special Features section above for more details.

Outside of Nicholas, scatterometer data provide observations of
gentle to moderate E-SE winds over the eastern half of the Gulf
region, and over the SW Gulf. Seas are 3-5 in the eastern Gulf and
4-6 ft over the SW Gulf based on an altimeter pass. Fresh to
strong winds in the outer periphery of Nicholas dominates the NW
Gulf with seas of 8-12 ft.

For the forecast, an area of fresh to strong winds will persist
today over the NW Gulf between Nicholas and high pressure over
the SE United States. A ridge will build westward across the
Gulf waters in the wake of Nicholas producing mainly light to
moderate SE to S winds.

...CARIBBEAN SEA...

A pair of tropical waves are moving westward across the Caribbean
Sea. Please see the Tropical Waves section for more information.

Satellite derived wind data show mainly gentle to moderate trade
winds across much of the basin. Moderate to locally fresh winds
are noted in the Windward passage, Gulf of Honduras and near the
coast of Colombia. Seas are generally 2-4 ft.

For the forecast, gentle to moderate trades will prevail across
the basin today and Wed. By Wed night, moderate to fresh winds
will return in the Gulf of Honduras and the south-central
Caribbean. This pattern will continue through the remainder of
the forecast period.

...ATLANTIC OCEAN...

High pressure dominates the Atlantic forecast waters with a 1021
mb high center W of Bermuda near 33N70W. Another high pressure
center of 1023 mb is located near 33N41W. A trough, reflection of
an upper-level is analyzed from 27N68W to 20N70W. Scattered
moderate convection is noted on either side of the trough covering
the waters from 20N-30N between 65W-70W. Based on streamlines
analysis and scatterometer data another trough is W of the Cabo
Verde islands and runs from 21N27W to 12N30W. A 1011 mb low is
along the trough axis. Mainly low clouds are associated with these
features. A stationary front cross the Canary Islands where
northerly winds have been reported. Recent altimeter pass indicates
seas 3 to 5 ft near the Canary Islands and north of 20N E of 55W.

For the forecast west of 65W, an area of low pressure is expected
to form by midweek a couple of hundred miles north of the
southeastern or central Bahamas as a tropical wave interacts with
an upper-level trough. Some gradual development of this system is
possible thereafter, and a tropical depression could form later
this week while the system moves north-northwestward or northward
across the western Atlantic.

For the forecast east of 65W, see the Special Features section
for more details on the tropical wave located over the far
eastern tropical Atlantic.

$$
Hagen/Torres
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