[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181805
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Mon Sep 18 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...

Hurricane Nigel is centered near 27.2N 51.4W at 18/1500 UTC or
about 760 nm ESE of Bermuda, and moving NW at 10 kt. Estimated
minimum central pressure is 984 mb. Maximum sustained winds are
70 kt with gusts to 85 kt. Seas are peaking near 29 ft near and
just north of the center. Numerous moderate to isolated strong
convection is found near and up to 130 nm in a W semicircle.
Scattered moderate convection is present up to 80 nm in a E
semicircle from the center, and near an outer rainband farther
north from 28N to 31N between 45W and 55W. Nigel will continue on
its current motion for the next couple of days, before turning
northward by Tuesday and accelerate toward the northeast
afterward. Intensification is expected and Nigel could become a
major hurricane on Tuesday, then gradually weaken by midweek.

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 newly analyzed tropical wave is off the Africa coast near 19W
from 18N southward, and moving west around 5 kt. Scattered
moderate convection is found from 4N to 18N between the
Mauritania-Liberia coast and 22W.

A central Atlantic tropical wave is near 42W from 12N southward,
and moving west at 10 to 15 kt. Widely scattered moderate
convection is noted from 05N to 12N between 38W and 44W.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic near the Gambia-Guinea
Bissau border then extends west-southwestward across 08N30W to
06N44W. An ITCZ continues from 06N44W to 07N52W. Scattered
moderate convection is evident up to 200 nm south of the trough
between 22W and 38W, and up to 300 nm north of the trough between
27W and 38W. Widely scattered moderate convection is seen up to
100 nm along either side of the ITCZ.

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
Tampa, Florida to the central Gulf, then turns northwestward as a
stationary front to near Corpus Christi, Texas. Widely scattered
showers and isolated thunderstorms are occurring along and up to
80 nm south of this boundary. A surface trough at the western Bay
of Campeche is causing similar conditions at the southwestern
Gulf, including the Bay of Campeche. A pre-frontal trough is
triggering isolated thunderstorms over southern Florida, including
the Florida Keys. Gentle to moderate NNE to NE winds and seas of 2
to 3 ft exist near and north of the frontal boundary. Light to
gentle winds and 1 to 2 ft seas prevail south of the frontal
boundary, including the Florida Straits.

For the forecast, the entire frontal boundary will become
stationary and weaken tonight. Winds will be moderate or weaker
with slight seas through Thu, pulsing to between moderate and
fresh offshore western Yucatan in the evenings. At the
northeastern Gulf, both winds and seas will increase by the end
of the week due to building high pressure north of the area.

...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 to 3 ft are
noted at the northwestern basin. Gentle monsoonal winds with seas
at 2 to 4 ft exist offshore from Costa Rica and Panama. Gentle to
moderate NE to SE winds and 3 to 5 ft seas prevail for the rest of
the basin.

For the forecast, long-period N to NE swell may impact the
Caribbean passages and Tropical North 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 off the Carolina coast
across 31N78W to near Daytona Beach, Florida. A pre-frontal trough
extends northeastward from southern Florida to just south of
Daytona Beach. Widely scattered showers and isolated thunderstorms
are found from the central Bahamas northward between 72W and the
Florida coast. Gentle to moderate SW to NW winds and 4 to 6 ft are
present in this area. Convergent southerly winds feeding toward
Hurricane Nigel are triggering scattered moderate convection from
17N to 28N between 44W and 48W. A surface trough along with
remnants of a shear line are causing scattered moderate convection
from 19N to 24N between 20W and 35W. 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, fresh to strong SE
to SW winds and seas of 8 to 12 ft are evident north of 22N
between 42W and 48W. Otherwise, moderate to locally fresh NNE to E
winds with 6 to 8 ft seas in large northerly swell exist north of
19N between the Africa coast and 48W. West of Nigel to 70W and north
of 20N, gentle with locally moderate NE to SE winds and seas of 4
to 6 ft in moderate mixed swells prevail. For the tropical
Atlantic from 06N to 20N between 42W and the Lesser Antilles,
light to gentle winds and 4 to 6 ft in moderate mixed swells are
present. Farther east, gentle to moderate NNE to NE winds and 3 to
5 ft seas are noted from 09N to 19N between the central Africa
coast and 42W, including Cabo Verde Islands. Gentle to moderate
monsoonal and southerly winds and seas of 4 to 6 ft in moderate
southerly swell prevail elsewhere in the Atlantic Basin.

For the forecast W of 55W, Nigel will strengthen to a major
hurricane near 30N54W early Tue, move to near 35N 54.5W early Wed,
then begin to slowly weaken as it moves to near 40N48W early Thu.
The cold front will reach from near 31N72W to near Jupiter,
Florida Tue morning, then stall over the northern forecast waters
through the end of the week. Winds and seas may increase west of
the stalled boundary by the end of the week as a tight pressure
gradient develops due to building high pressure inland and a
developing coastal trough off the Carolinas.

$$

Forecaster Chan
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