[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111756
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Mon Sep 11 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 1200 UTC surface analysis and satellite imagery through
1750 UTC.

...SPECIAL FEATURES...

Major Hurricane Lee is centered near 23.5N 63.5W at 11/1500 UTC
or 320 nm N of the Northern Leeward Islands, moving to the northwest
at 7 kt. Estimated minimum central pressure is 948 mb. Maximum
sustained wind speed is 105 kt with gusts to 130 kt. Recent
satellite imagery and aircraft data have indicated concentric
eyewalls, with ongoing eyewall replacement cycles. Numerous
moderate to scattered strong convection is forming the northern
lobe of an inner eyewall within 45 nm in the northern semicircle
of Lee. Scattered moderate convection is evident within 90 nm in
the southeast semicircle of the hurricane, and clusters of
thunderstorms between 150 to 180 nm in the northern semicircle. As
The wave field continues to expand from Lee as it makes its turn
northward. Seas in excess of 12 ft reach as far as 330 nm in the
northern semicircle, and 270 nm in the southern semicircle.
Surrounding seas associated with Lee will bring dangerous surf and
life-threatening rip currents to portions of the northern Leeward
Islands, the Virgin Islands, Puerto Rico, Hispaniola, the Turks
and Caicos Islands, the Bahamas, Bermuda, and most of the U.S East
Coast through much of the week. Please consult products from your
local weather office.

Tropical Storm Margot is centered near 26.1N 40.0W at 11/1500 UTC
or 1080 nm NW of the Cabo Verde Islands, moving to the north at 9
kt. Estimated minimum central pressure is 993 mb. Maximum
sustained wind speed is 60 kt with gusts to 75 kt. Scattered
moderate to isolated strong convection is evident within 90 nm of
the center of Margot, and seas in excess of 12 ft are noted within
180 nm of the center. Margot may strengthen slightly as it
continues to move northward over the next couple of days.

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 on Lee and Margot at
www.hurricanes.gov for more details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave is along 22W, to the south
of 19N, and moving west around 5 to 10 kt. Scattered moderate
isolated strong convection is from 08N to 13N between 22W and
27W. Environmental conditions appear conducive for gradual
development of this system during the latter part of this week,
and a tropical depression could form by next weekend as it moves
westward to west-northwestward over the central tropical Atlantic.
There is a low chance of tropical cyclone formation during the
next two days and a medium chance from 3 to 7 days.

An eastern Atlantic tropical wave is analyzed along 31W, south of
16N, moving westward around 5 to 10 kt. A 1014 mb low pressure
center (Invest AL97) is near 13N 31W. Scattered moderate isolated
strong convection is noted from 12N to 13N between 32W and 34W.
This system is forecast to merge with the aforementioned tropical
wave to the east in a couple of days. As a result, there is a low
chance of tropical cyclone formation during the next 7 days.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic near over the coast of
Senegal near 15N17W then reaches southwestward through the low
(Invest AL97) near 13N31W to 14N35W. The ITCZ reaches from 11N53W
to 10N61W. Convection is described above in the tropical wave
sections.

...GULF OF MEXICO...

A surface trough reaches from off the mouth of the Mississippi
River in the north-central Gulf to off Tampico, Mexico in the
west-central Gulf. Farther east, a weak ridge extends from the
western Atlantic into the northeastern Gulf. This pattern is
supporting only light to gentle breezes and slight seas across
the basin. No significant shower or thunderstorm activity is
evident.

For the forecast, the weak ridge will dominate the Gulf waters
throughout the forecast period supporting light to gentle winds.
Scattered thunderstorms can be expected across the western
Yucatan and eastern Bay of Campeche each late afternoon and
evening.

...CARIBBEAN SEA...

Please read the Special Features section about large swell
generated by Major Hurricane Lee impacting the northeast Caribbean
islands.

Divergent flow aloft is assisting a few clusters of thunderstorms
over the western Caribbean, south of the Isle of Youth, over parts
of the Gulf of Honduras, and just east of Providencia Island. The
subtropical ridge that is normally present north of the basin is
being disrupted in part by Hurricane Lee. This pattern is
supporting gentle to moderate breezes. Swell from Lee is
penetrating the Mona and Anegada Passages, with combined seas of 6
to 8 ft in the passages, with plumes of 4 to 6 ft swell south of
the passages over the northeast Caribbean. Combined seas are 2 to
4 ft elsewhere.

For the forecast, moderate to fresh trade winds will continue in
the central and eastern basin through this evening before Lee in
the Atlantic disrupts the pressure pattern. The large easterly
swell across the adjacent Atlantic will gradually become NE and
then N today through Thu, and move through the Caribbean Passages
and into the Caribbean waters between the Leeward Islands and the
Mona Passage. Seas across these Caribbean Passages and waters will
diminish significantly Thu night through Fri.

...ATLANTIC OCEAN...

Please see the Special Features section for information about
Hurricane Lee and Tropical Storm Margot.

Outside of the weather described above associated with the
tropical waves and tropical cyclones, no significant convection
is noted across the basin. Weak low pressure near 14.5N47.5W is
producing a small cluster of scattered moderate convection.

A recent scatterometer satellite pass indicated a compact but
weak swirl in the wind field near 14N48W, with only 5 to 10 kt
winds near it. It is in an area of almost calm breezes over the
western tropical Atlantic. The scatterometer passes also revealed
a band of moderate E to SE winds over the eastern Atlantic from
the coast of Western Sahara toward T.S. Margot, south of 1020 mb
high pressure centered near 30N26W. Gentle breezes are noted
elsewhere across the Atlantic outside of the areas near Lee and
Margot, with combined seas of 4 to 6 ft in mixed swell.

For the forecast west of 55W, Lee is expected to maintain a slow
NW motion and strengthen modestly through Tue, then begin a
gradual turn toward the N on Wed.Lee will move to 23.9N 64.4W this
evening, 24.4N 65.5W Tue morning, 24.9N 66.5W Tue evening, 25.7N
67.2W Wed morning, 27.0N 67.7W Wed evening, and 28.8N 68.0W Thu
morning. Lee will change little in intensity as it moves N of the
area early Fri. Large E to SE swell dominating the waters east of
76W early this morning will continue to propagate westward across
the Atlc, reaching the NW Bahamas and 78W late this afternoon or
evening, and the Florida coasts Tue afternoon. Large swell from
Lee will dominate regional waters Tue night through Fri.

$$
Christensen
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