399
AXNT20 KNHC 242333
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Wed Sep 25 2024

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
2300 UTC.

...SPECIAL FEATURES...

Tropical Storm Helene is centered near 19.7N 84.7W at 24/2100
UTC or 130 nm ESE of Cozumel Mexico, moving WNW at 10 kt.
Estimated minimum central pressure is 995 mb. Maximum sustained
wind speed is 45 kt with gusts to 55 kt. Seas 12 ft or greater are
occurring within 120 NM in the NE quadrant and 150 NM in the SE
quadrant, with peak seas near 16 ft. Strong convection is
occurring within 120 NM to the north, east and southeast of the
center, and additional moderate to strong convection is noted
across much of the western Caribbean. Additional strengthening is
forecast, and Helene is expected to become a hurricane on
Wednesday. The storm is forecast to rapidly strengthen over the
eastern Gulf of Mexico and become a major hurricane on Thursday.
Helene will move to 20.4N 86.0W Wed morning, 21.7N 86.6W Wed
afternoon, 23.7N 86.1W Thu morning, 27.0N 84.9W Thu afternoon,
move inland and weaken to a tropical storm near 31.5N 84.0W Fri
morning, and move inland and weaken to a tropical depression near
35.5N 84.8W Fri afternoon. Helene will move inland over 38.2N
89.0W Sat afternoon. Helene is expected to produce total rain
accumulations of 4 to 8 inches over western Cuba and the Cayman
Islands with isolated totals around 12 inches. Over the eastern
Yucatan Peninsula, 4 to 6 inches of rain are expected with
isolated totals over 8 inches. Over the Southeastern U.S., Helene
is expected to produce total rain accumulations of 4 to 8 inches
with isolated totals around 12 inches. This rainfall will likely
result in areas of considerable flash and urban flooding, with
areas of significant river flooding likely, including the risk of
landslides in areas of steep terrain in the southern Appalachians.
The combination of a dangerous storm surge and the tide will
cause normally dry areas near the coast to be flooded by rising
waters moving inland from the shoreline, with impacts felt from
the Florida Keys to the panhandle of Florida, as well as
northeastern Florida through the central South Carolina coast.

HIGH SEAS FORECAST issued by the National Hurricane Center at
website - https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the
latest Helene NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

...TROPICAL WAVES...

A tropical wave in the eastern Atlantic is near 28W from 19N
southward, moving toward the west at 10-15 kt. Scattered moderate
to locally strong convection is noted from 12N to 16N between 28W
and 33W. Environmental conditions appear favorable for gradual
development of this system, and a tropical depression is likely to
form in a few days while it moves westward to west-northwestward
across the eastern and central tropical Atlantic. There is a
medium chance of tropical formation in the next 48 hours, and a
high chance of formation in the next seven days.

A tropical wave approaching the Lesser Antilles is near 50W from
17N southward, moving westward at 5-10 knots. Scattered moderate
to strong convection is occurring from 11N to 17N between 50W and
61W.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic near 12N17W, then curves
southwestward to near 09N38W. The ITCZ extends from 09N38W to
09N50W. Scattered moderate to locally strong convection is noted
from 04N to 09N between 21W and 34W.

...GULF OF MEXICO...

Please refer to the Special Features section above for details on
Tropical Storm Helene. Moderate E winds and seas are increasing
in the far SE Gulf of Mexico, including the Florida Straits and
Yucatan Channel, in association with Helene.

Weak ridging across the rest of the basin supports light to gentle
winds and slight seas. Scattered moderate convection is occurring
off the coast of Texas and far northern Mexico ahead of an
approaching cold front.

For the forecast, away from the immediate impacts from Helene,
increasing NE winds are expected tonight into Wed over the western
Gulf, becoming moderate to locally fresh N winds into Thu, then
gradually becoming NW and weakening on Fri. Seas will become
moderate to rough over the aforementioned area. Widespread showers
and thunderstorms will also occur across much of the basin, with
gusty winds and rough seas expected near convection.

...CARIBBEAN SEA...

Please refer to the Special Features section above for details on
Tropical Storm Helene. Away from Helene, moderate to locally fresh
SE winds and moderate seas are occurring across much of the basin.

For the forecast, away from the immediate impacts from Helene,
fresh to strong S to SE winds will persist after Helene moves
northward out of the basin late Wed into Thu, and very rough seas
will accompany these winds. Elsewhere, E to SE trades will
continue. By Fri into this weekend, a seasonal trade regime with
slight to moderate seas will prevail.

...ATLANTIC OCEAN...

Please refer to the Tropical Waves section for information on
potential tropical development in the eastern Atlantic this week.

A 1004 mb low is centered near 39N58W, and surface troughing
extends from 31N56W to 22N70W. Scattered moderate convection is
occurring along and ahead of this trough. A secondary trough
is noted from 31N61W to off the coast of northeast Florida.
Elsewhere, a 1024 high dominates eastern portions of the
Atlantic. The pressure gradient between this ridge and a 1012 mb
low over northwest Algeria supports fresh to locally strong NE
winds downwind of the Canary Islands.

For the forecast W of 55W, increasing S to SE winds will develop
off the coast of Florida ahead of Helene, and showers and
thunderstorms will accompany these winds. The tropical wave near
the Cabo Verde Islands will encounter environmental conditions
that will be favorable for gradual development of this system, and
a tropical depression is likely to form in a few days while it
moves westward to west-northwestward across the eastern and
central tropical Atlantic. There will be a medium chance of
tropical development in the next 48 hours, and a high chance of
development in the next seven days.

$$
ADAMS