[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 182107
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Tue Sep 19 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 1800 UTC surface analysis and satellite imagery through
2000 UTC.

...SPECIAL FEATURES...

Hurricane Nigel is centered near 28.0N 52.2W at 18/2100 UTC or
700 nm ESE of Bermuda, moving NW at 10 kt. Estimated minimum
central pressure is 982 mb. Maximum sustained wind speed is 70
kt with gusts to 85 kt. Seas are peaking near 31 ft near and
just north of the center. Numerous moderate to isolated strong
convection is found near and up  to 240 nm in the SW semicircle
and 120 nm in the NE semicircle. Nigel is forecast to turn
northward late Tuesday, and then accelerate northeastward through
the rest of the week. Nigel is expected to strengthen during the
next couple of days. A gradual weakening trend is forecast to
begin by late Wednesday.

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 Nigel
NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov
for more details.

...TROPICAL WAVES...

A tropical wave is off the Africa coast near 19W/20W from 18N
southward, and moving west around 5 kt. Scattered moderate
convection is found from 03N to 07N between 20W and 28W.

A central Atlantic tropical wave is near 43W from 12N southward,
and moving west at around 10 kt. Widely scattered moderate
convection is noted from 04N to 12N between 32W and 43W.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic near the Gambia-Guinea
Bissau border near 13N17W then extends west-southwestward across
10N21W to 07N44W. An ITCZ continues from 07N44W to 07N53W. Other
than the convection described in the Tropical Waves section,
scattered moderate isolated strong convection is evident from 05N
to 07N between 47W and 54W.

The eastern end of the East Pacific monsoon trough is producing
numerous showers and scattered thunderstorms across the Caribbean
waters north of Costa Rica, Panama and northwestern Colombia.

...GULF OF MEXICO...

A modest cold front reaches west-southwestward from just north of
Fort Myers, Florida to 25.5N86W, then turns west-northwestward as
a dissipating stationary front to near Brownsville, Texas. Widely
scattered showers and isolated thunderstorms are occurring from
the NE Gulf to the SW Gulf. A surface trough at the western Bay
of Campeche is causing scattered showers. Moderate NE winds are
occurring N of the boundary with mainly gentle winds elsewhere.
Seas are 2-4 ft N of the boundary and 1-2 ft elsewhere outside of
any convection.

For the forecast, the front will become stationary this evening
and dissipate Tue. Winds will be moderate or weaker with slight
seas through Thu, pulsing to moderate to fresh offshore the W
Yucatan in the evenings. Winds may freshen in the NE Gulf by the
end of the week due to building high pressure north of the area
with seas also building.

...CARIBBEAN SEA...

An upper-level trough runs east-northeastward from a low near the
Island of Youth across Jamaica and Hispaniola. These features are
inducing isolated thunderstorms across the northwestern and
north-central basin. Refer to the Monsoon Trough/ITCZ section for
additional weather in the Caribbean Basin.

A modest trade-wind pattern continues for much of the basin. Fresh
ENE to ESE winds and 4 to 6 ft seas are present at the south-
central basin. Light to gentle winds and seas of 1-3 ft are noted
at the northwestern basin. Gentle monsoonal winds with seas at 3-4
ft exist offshore from Costa Rica and Panama. Gentle to moderate
NE to SE winds prevail for the rest of the basin, except fresh to
strong offshore N Colombia and NW Venezuela. Seas are 4-6 ft there
and 3-5 ft across the remainder of the waters.

For the forecast, long period north to northeast swell may impact
the Caribbean passages and Tropical N Atlantic through the early
part of this week. Moderate to fresh trades will prevail in the
central Caribbean, locally strong at times offshore northern
Colombia, with moderate or weaker winds elsewhere through the
week.

...ATLANTIC OCEAN...

Please read the Special Features section for details about
Hurricane Nigel.

A modest cold front runs southwestward from well off the Carolina
coast across 31N75W to near Fort Pierce, Florida. A pre-frontal
trough extends northeastward from near the NW Bahamas to the
Straits of Florida. Widely scattered showers and isolated
thunderstorms are found from N of 30N and within 150 nm E of the
front. Mainly moderate winds are behind and just N of the front
along with 4-6 ft seas. Refer to the Monsoon Trough/ITCZ and
Tropical Waves sections at the beginning for additional convection
in the Atlantic Basin. Outside the direct impact of Hurricane
Nigel, a belt of fresh to strong trades is noted from 19N to 30N
between the coast of Africa and 40W along with 8-11 ft seas.
Moderate trades and 5-8 ft seas are found elsewhere N of 10N and E
of 45W, with mainly gentle winds and 5-7 ft seas across the
remainder of the tropical Atlantic waters.

For the forecast W of 55W, Nigel will move to near 31N 54.5W Tue
afternoon, 36N 53.5W Wed afternoon, then begin to slowly weaken
as it moves to near 42N44W Thu afternoon. A cold front extending
from 31N75W to Stuart, FL will reach from near 31N72W to near West
Palm Beach, Florida Tue, then stall over the northern forecast
waters through Thu. The boundary should begin moving N Fri as low
pres develops along it, to the east of northern Florida. Winds and
seas will likely increase in that area by the end of the week as
a tight pressure gradient develops between the developing low pres
off the Carolinas and high pressure inland over the U.S.

$$
Lewitsky
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