[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231758
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Mon Oct 23 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
1630 UTC.

...SPECIAL FEATURES...

Hurricane Tammy: Hurricane Tammy is centered near 21.9N 63.9W at
23/1500 UTC or 225 nm N of Anguilla, and moving N at 6 kt.
Estimated minimum central pressure is 993 mb. Maximum sustained
winds are 70 kt with gusts to 85 kt. Seas are peaking at 22 to 23
ft near the center. Numerous moderate to isolated strong
convection is seen near and up to 100 nm in a NE semicircle from
the center. A turn toward the NE is expected to begin later today
with a slight increase in forward speed by Tue. Some modest
strengthening is anticipated for the next couple of days. Please
read the latest HIGH SEAS FORECAST issued by the National
Hurricane Center, at the website -
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml, and the latest
Tammy NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov, for more details.

Southwestern Caribbean Low Pressure (Invest-AL95): A 1006 mb low
pressure centered near 11N82W is producing numerous moderate to
isolated strong convection from 11N to 13N between the Nicaragua
cost and 81W. Scattered moderate convection is found farther north
from 13N to 15W betwen the northern Nicaragua coast and 80W.
Fresh to locally strong winds and seas of 4 to 6 ft are present in
these areas. The showers and thunderstorms continue to show signs
of organization, and environmental conditions appear to be
favorable for development. A short-lived tropical depression could
form before the system moves inland over Nicaragua by early Tue.
Regardless of development, this system could produce heavy rains
over portions of Central America during the next couple of days.
There is a medium chance of tropical formation within the next 48
hours. Please refer to the latest NHC Tropical Weather Outlook, at
www.hurricanes.gov, for more details.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic along the Guinea coast just
north of Conakry, then curves west-southwestward to near 08N25W.
Farther west, an ITCZ extends westward from 08N39W to 08N54W.
Scattered moderate convection is noted near the trough from 03N to
12N between the Guinea-Liberia coast and 24W, and up to 160 nm
north and 100 nm south of the ITCZ.

...GULF OF MEXICO...

A very weak cold front stretches west-northwestward from near
Tampa, Florida to near New Orleans, Louisiana. There is no
significant convection related to this feature. A broad surface
ridge dominates the rest of the Gulf, converging southeasterly
winds are causing scattered showers at the SW Gulf, including the
Bay of Campeche. Moderate to fresh SE winds and seas of 4 to 6 ft
seas are seen at the NW Gulf, while gentle to moderate E to SE
winds and 2 to 4 ft seas are evident for the remainder of the
Gulf.

For the forecast, the weak cold front will slide eastward and
dissipate later today. High pressure will build southward in its
wake. This will lead to increasing winds early this week, with
fresh to locally strong E winds and building seas Mon night
through Thu night.

...CARIBBEAN SEA...

Please read the Special Features section above for details on a low
pressure (Invest AL95) in the far southwestern basin that has the
potential to become a tropical depression within the next 48
hours.

A surface trough is triggering scattered showers and isolated
thunderstorms in the northwestern basin just south of the Yucatan
Channel and north of the Cayman Islands. Converging southerly
winds feeding toward Hurricane Tammy well northeast of Puerto
Rico are generating similar convection over the northern Leeward
Islands. Other than the area near AL95, gentle to moderate E to
SSW winds and seas of 2 to 4 ft are noted south of 17N and east of
82W. Moderate to fresh ENE to SSW winds and 4 to 6 ft seas
prevail for the rest of the basin.

For the forecast, Hurricane Tammy will move northward and farther
away from the area today, with impacts from the system decreasing
over the forecast area. Invest AL95 will maintain fresh to locally
strong winds and higher seas at the far southwestern basin through
Tue.

...ATLANTIC OCEAN...

Please read the Special Features section at the beginning about
Hurricane Tammy.

A weak cold front curves west-southwestward from near Bermuda
across 31N66W to near Melbourne, Florida. No significant
convection is found near the front. A stationary front extends
southwestward from east of Bermuda across 31N62W and the southeast
Bahamas to the eastern end of Cuba. Scattered moderate convection
is noted near and south of this feature from 24N to beyond 31N
between 59W and 67W. Aided by divergent flow south of an upper-
level low near 20N48W, convergent easterly trades are producing
widely scattered moderate convection from 11N to 16N between 41W
and 53W. Refer to the Monsoon Trough/ITCZ section at the beginning
for additional convection in the Atlantic Basin.

A large dome of 1025 mb high near 33N34W is providing gentle to
moderate NNE to E to SE winds north of 20N between the northwest
Africa coast and 50W. Within this same area, large north swell is
creating 6 to 9 ft seas. To the west near the stationary front but
outside the direct impact of Hurricane Tammy, gentle to moderate
with locally fresh E to S winds and seas of 5 to 8 ft are evident
north of 20N between 50W and 65W. Farther west, gentle to moderate
NE winds and 4 to 6 ft seas are found from the Bahamas northward
west of 65W. From 10N to 20N, moderate to fresh ENE to SE winds
and seas at 5 to 7 ft exist between 40W and the Lesser Antilles.
Near the Cabo Verde Islands, gentle to moderate NNE to ENE winds
and 4 to 7 ft seas are present from 08N to 20N between the central
Africa coast and 40W. Light to gentle with locally moderate
monsoonal and southerly winds and seas at 4 to 6 ft prevail
elsewhere in the Atlantic Basin.

For the forecast W of 55W, Hurricane Tammy will move to 22.7N
63.4W this evening, 23.6N 62.4W Tue morning, and near 24.5N 61.2W
Tue evening. By Wed morning, it will be near 25.8N 59.9W, then
27.3N 58.9W Wed evening, and weaken as an extratropical cyclone
near 29.1N 58.6W Thu morning. Tammy will change little in
intensity as it moves to near 31.2N 60.2W early Fri. The
stationary front mentioned earlier will remain in place this
week. High pressure will move off the east coast of the United
States later tonight, and build north of the forecast area through
midweek. The pressure gradient between the front, Tammy, and the
area of building high pressure will tighten. This will help to
develop of a broad area of strong NE winds and rough seas across
much of the area west of the boundary starting tonight and
continuing through the week.

$$

Forecaster Chan
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