[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 220920
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Fri Sep 22 2023

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
0900 UTC.

...SPECIAL FEATURES...

Potential Tropical Cyclone Sixteen is centered near 30.5N 75.0W
at 22/0900 UTC or 290 nm ESE of Charleston South Carolina,
moving N at 12 kt. Estimated minimum central pressure is 1000
mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. The
position of the low pressure is maintaining winds to gale force
and rough seas between the northeast coast of Florida and Bermuda.
A sharp upper trough west of the system is keeping areas of
showers and thunderstorms 90 to 180 nm to the north of the center.
Surface data from ships, saildrones, and via satellite are
showing gale force winds between the low pressure and the Carolina
coast. Regional buoy data is showing wave heights are building a
little above 12 ft within 180 nm in the northern half of the low
pressure off the Carolinas and Georgia. Additional strengthening
is forecast during the next day or so, and the low is expected to
become a tropical storm before it reaches the coast of North
Carolina. Regardless of whether it becomes a tropical storm, the
system is expected to bring tropical-storm conditions to portions
of the southeast and mid- Atlantic coasts. 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 Sixteen NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

Post-Tropical Cyclone Nigel is centered near 46.3N 32.6W at
22/0900 UTC or 560 nm NNW of the Azores, moving NE at 32 kt.
Estimated minimum central pressure is 976 mb. Maximum sustained
wind speed is 60 kt with gusts to 75 kt. The center of Nigel is
mostly exposed with weakening convection sheared to the northeast
of the center. Nigel will continue to gradually weaken over the
next couple of days as it moves quickly to the northeast, due to
the intense shear and cooler waters. However, the system will
remain a strong extra- tropical cyclone with an expanding wind
field. Hazards associated with Nigel will remain well north of
the TAFB forecast waters. Please read the latest HIGH SEAS
FORECAST issued by the Ocean Prediction Center at website under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php. Please see the latest Nigel
NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov
for more details.

Invest 90L in the eastern Tropical Atlantic: The axis of a
tropical wave is analyzed along 32W. A 1009 mb low pressure system
is near 13N along the wave axis where the monsoon trough
intersects the tropical wave. The disturbance is moving westward
at 10-15 kt. Showers and thunderstorms continue to show signs of
organization, within 180 nm north of the monsoon trough between
30W and 35W. Fresh to strong winds and seas of 7-10 ft are
occurring in the northern semicircle of the low pressure.
Environmental conditions are forecast to be conducive for gradual
development of this system, and a tropical depression is likely to
form this weekend or early next week while the system moves
generally westward at 10 to 15 mph across the eastern and central
tropical Atlantic. There is a medium chance of development through
48 hours. Please see the latest Tropical Weather Outlook at
www.hurricanes.gov for more information.

...TROPICAL WAVES...

Please see the Special Features Section for details on the
tropical wave (Invest 90L) along 32W.

A central Atlantic tropical wave has its axis along 56W, south of
21N, moving westward at 10-15 kt. No significant convection is
evident near the wave axis.

...MONSOON TROUGH/ITCZ...

The monsoon trough reaches the Atlantic through the coast of
Senegal near 14N16W and continues westward to 12N23W and then the
aforementioned low pressure near 13.5N30.5W, before terminating
near 10N50W. No significant convection is evident along the
monsoon trough outside of the area near the low pressure at
12N23W.

GULF OF MEXICO...

Weak high pressure over the lower Mississippi Valley is supporting
light to gentle NE to E breezes and slight seas across most of the
basin this morning. A recent scatterometer satellite pass
indicated the exception of moderate to fresh winds off the western
coast of Yucatan where an overnight trough is moving westward
over the Bay of Campeche. A few showers and thunderstorms are
active along the trough over the coast of the state of Tabasco.

For the forecast, the weak high pressure over the lower
Mississippi Valley and northern Gulf will be in control of the
weather pattern across basin through early next week. This pattern
will support mostly gentle to moderate east to southeast winds
and slight seas, except for moderate to fresh winds pulsing
offshore the western Yucatan Peninsula in the evenings as an
overnight trough moves off the coast into the Bay of Campeche.

CARIBBEAN SEA...

A recent scatterometer satellite pass indicated fresh to strong NE
winds off the coast of Colombia between Barranquilla and
Cartagena. The pass also showed moderate to locally fresh NE to E
winds across the Gulf of Honduras. These winds are due in part to
high pressure centered north of the area over the south-central
U.S., but also due to fairly deep 1007 mb pressure over Colombia.
Gentle to moderate trades persist elsewhere across the basin.
Combined seas are 2 to 4 ft, except 4 to 6 ft off Colombia.
Scattered showers and a few thunderstorms are noted in the
Windward Passage and eastern Caribbean due to divergent flow aloft
and trade wind convergence in the lower levels of the atmosphere.

For the forecast, the moderate to fresh trade winds in the
central Caribbean will change little through the next few days.
Fresh to strong trade winds will pulse offshore of northern
Colombia and northwest Venezuela during mainly the overnight and
early morning hours into early next week. Elsewhere moderate or
weaker winds will prevail with slight to moderate seas. Looking ahead,
combined seas will build northeast of the Leeward Islands by Tue
ahead of low pressure moving westward across the tropical
Atlantic, possibly as the next tropical cyclone.

ATLANTIC OCEAN...

Please see the Special Features section section above for
information on Potential Tropical Cyclone Sixteen and Invest 90L.

An upper level low near 22N52W and plenty of tropical moisture
are maintaining scattered moderate convection from 21N to 23N and
between 50W and 55W. An earlier scatterometer satellite pass
captured moderate to fresh easterly winds in the area described.
A recent altimeter satellite pass indicted 6 to 8 ft combined seas
over much of the Atlantic from 15N to 25N, likely due to NE
swell. The remainder of the Atlantic south of 31N is dominated by
a broad subtropical ridge, suppressing the development of deep
convection. Moderate to locally fresh NE winds are also noted in
the eastern Atlantic, from 15N to 25N and east of 20W. Seas in
this region are 5-7 ft. Elsewhere, moderate or weaker winds and
moderate seas prevail.

For the forecast west of 55W, Potential Tropical Cyclone Sixteen
is near 29.6N 75.3W at 11 PM EDT, and is moving north-northeast at
6 kt. Maximum sustained winds are 35 kt with gusts to 45 kt, and
the minimum central pressure is 1007 mb. Sixteen will move to
31.2N 75.5W Fri morning, then continue to move north of the area
to the coast of North Carolina through early Sat. A weak ridge
will build in the wake of Sixteen off northeast Florida through
early next week, although a trough will persist across the
Bahamas. Looking ahead, combined seas will build northeast of the
Leeward Islands by Tue ahead of low pressure moving westward
across the tropical Atlantic, possibly as the next tropical
cyclone.

$$
Christensen
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