[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171802
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Sun Sep 17 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
1700 UTC.

...SPECIAL FEATURES...

Post-Tropical Cyclone Lee is centered near 48.0N 62.0W at 17/1500
UTC or 115 nm WNW of Port Aux Basques, Newfoundland and moving NE
at 19 kt. Estimated minimum central pressure is 989 mb. Maximum
sustained winds are 40 kt with gusts to 50 kt. An increase in
forward speed toward the NE is expected over the next couple of
days, bringing Lee over Newfoundland this afternoon and the
northern Atlantic waters by early Monday. Gradual weakening will
continue during the next couple of days, and Lee could dissipate
on Tuesday. Please read the latest HIGH SEAS FORECAST issued by
the Ocean Prediction Center at website -
https://www.ocean.weather.gov/shtml/NFDHSFAT1.php for more
details.

Post-Tropical Cyclone Margot is centered near 34.6N 42.4W at
17/1500 UTC or 770 nm W of the Azores, and moving WNW at 8 kt.
Estimated minimum central pressure is 1001 mb. Maximum sustained
winds are 35 kt with gusts to 45 kt. Seas are peaking near 20 ft
near the center. Scattered showers are seen within 150 nm of the
center. A clockwise turn resulting in a motion toward the east is
expected over the next couple of days. Small fluctuations in
intensity are expected during the next few days. Please read the
latest HIGH SEAS FORECAST issued by the Ocean Prediction Center at
website - https://www.ocean.weather.gov/shtml/NFDHSFAT1.php for
more details.

Tropical Storm Nigel is centered near 24.0N 49.1W at 17/1500 UTC
or 860 nm NE of the Lesser Antilles,and moving NNW at 11 kt.
Estimated minimum central pressure is 997 mb. Maximum sustained
wind speed is 50 kt with gusts to 60 kt. Peak seas range from 21
to 23 ft near the center. Scattered moderate to isolated strong
convection is seen near and up to 170 nm in a northern semicircle
from the center. Niger will continue its current motion over the
next couple of days, then turn northward on Tuesday before turning
northeastward with increasing speed afterward. Additional
strengthening is expected and Nigel will likely become a hurricane
tonight or Monday. Nigel is forecast to approach major hurricane
intensity by mid-week. Please read the latest HIGH SEAS FORECAST
issued by the National Hurricane Center at website -
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details.

For the latest NHC Forecast/Advisories and Public Advisories on
all three systems, visit www.hurricanes.gov for more details.

...TROPICAL WAVES...

An eastern Atlantic tropical wave is near 37W from 12N southward,
and moving westward 10 to 15 kt. Widely scattered moderate
convection is found from 05N to 12N between 34W and 38W.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic at the Gambia coast, then
extends west-southwestward through 10N21W to 09N27W. An ITCZ
continues from 09N27W to 09N34W, then resumes from 06N39W to
05N47W. Scattered moderate convection is occurring near and south
of the trough from 05N to 13N between the Gambia-Sierra Leone
coast and 27W. Widely scattered moderate convection is present
near and up to 140 nm north of the first ITCZ segment.

The eastern end of the East Pacific monsoon trough is triggering
scattered showers and thunderstorms across the Caribbean waters
south of 12N, west of 76W near Costa Rica and Panama.

...GULF OF MEXICO...

A modest cold front reaches west-southwestward from a 1013 mb low
near Mobil, Alabama to just south of Brownsville, Texas. Widely
scattered showers and isolated thunderstorms are seen near and up
to 40 nm south of the front. A surface trough near the northern
Mexico coast is producing scattered showers and thunderstorms from
22N to 24N west of 92W. Another surface trough is causing similar
conditions at the western Bay of Campeche. Gentle to moderate
northerly winds and seas of 2 to 3 ft are present near the cold
front. Otherwise, weak surface ridging is maintaining light to
gentle winds and 1 to 2 ft seas for the rest of the Gulf.

For the forecast, the cold front will move farther south into the
northern Gulf this evening, then followed by another reinforcing
cold front on Mon. A wind shift along with some isolated to
scattered thunderstorms will occur with these frontal boundaries.
Winds will be moderate or weaker with slight seas through Thu,
pulsing to between moderate and fresh offshore the western
Yucatan Peninsula in the evenings. Winds may freshen in the
northeastern Gulf by the end of the week due to a building high
north of the area.

...CARIBBEAN SEA...

Refer to the Monsoon Trough/ITCZ section for weather in the
Caribbean Basin. A weak 1019 mb Bermuda High near 33N71W is
supporting a modest trade-wind pattern across much of the
Caribbean Sea. Moderate to fresh ENE to E winds and seas of 4 to 6
ft are evident at the south-central basin. Mainly gentle NE to E
winds and 1 to 3 ft seas are seen at the northwestern basin,
including the Gulf of Honduras. Gentle to moderate NE to ESE winds
and seas at 3 to 4 ft prevail for the rest of the basin.

For the forecast, moderate to large N-NE swell may impact the
Caribbean passages and Tropical north Atlantic through the early
part of the 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...

See the Special Features Section for more details on Post-Tropical
Cyclones Lee and Margot, and Tropical Storm Nigel.

A surface trough is generating scattered showers and
thunderstorms from the northwest Bahamas northward to 31N, west of
75W. An upper-level low near 27N57W is producing widely scattered
convection from 21N to 29N between 56W and 60W. A cold front
curves westward from the Mauritania-Western Sahara border to
26N22W, then turns northwestward to beyond 31N29W. Patchy rain are
occurring near and up to 140 nm south of this feature. Refer to
the Monsoon Trough/ITCZ and Tropical Waves sections at the
beginning for additional weather in the Atlantic Basin.

Fresh to strong NE to E winds and seas of 9 to 12 ft are present
from 25N to 29N between 44W and 52W. Otherwise outside the direct
impact of Tropical Storm Nigel, gentle to moderate with locally
fresh NNE to SE winds and 5 to 8 ft seas in moderate northerly
swell exist north of 20N between the northwest Africa coast and
55W. Farther west, light to gentle with locally moderate E to SE
winds and seas at 5 to 7 ft in moderate northerly swell are noted
north of 20N between 55W and the Georgia-Florida coast, including
the Canary Islands. Near the Cabo Verde Islands, Gentle to
moderate NW to NE winds and 4 to 6 ft seas are found from 10N to
20N between the central Africa coast and 40W. To the west, light
to gentle winds and 3 to 6 ft seas in mixed swells are present
from 05N to 20N between 40W and the Lesser Antilles. Light to
gentle with locally moderate southerly winds and seas at 4 to 6 ft
in moderate southerly swell prevail for the remainder of the
Atlantic Basin.

For the forecast W of 55W, Tropical Storm Nigel will move to
25.3N 50.2W this evening, then strengthen to a hurricane near
26.8N 51.7W Mon morning. Afterward, it is going to track near
28.2N 53.1W Mon evening, 29.8N 54.6W Tue morning, then into the
northern Atlantic near 31.8N 55.4W Tue evening, 34.2N 54.9W Wed
morning. Otherwise, weak ridging will prevail this afternoon into
the evening. A cold front will move off the northeastern Florida
coast tonight, reaching from 31N72W to near Jupiter, Florida Tue
morning, then stalling along 28N/29N through the end of the week.
Winds may increase west of the stalled front by the end of the
week as a tight pressure gradient develops due to a building high
inland and a developing coastal trough off the Carolinas.

$$

Forecaster Chan
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