594
AXNT20 KNHC 260602
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 UTC Thu Sep 26 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 0000 UTC surface analysis and satellite imagery through
0600 UTC.

...SPECIAL FEATURES...

Hurricane Helene is centered near 23.7N 86.5W at 26/0600 UTC or
330 nm SW of Tampa Florida, moving N at 10 kt. Estimated minimum
central pressure is 971 mb. Maximum sustained wind speed is 75 kt
with gusts to 90 kt. Seas 12 ft or greater are occurring within
240 NM in the NE quadrant, 270 NM in the SE quadrant, and 150 NM
in the SW and NW quadrants with peak seas near 36 ft. Moderate
convection is occurring within 120 NM to the south and west of the
center, with scattered moderate to locally strong convection
occurring within 200 NM to the north and east of the center.
Strengthening is forecast, and Helene is expected to be a major
hurricane when it reaches the Florida Big Bend coast Thursday
evening. Weakening is expected after landfall, but Helene`s fast
forward speed will allow strong, damaging winds, especially in
gusts, to penetrate well inland across the southeastern United
States, including over the higher terrain of the southern
Appalachians. A northward or north-northeastward motion at a
faster forward speed is expected during the next 24 hours. Helene
will move to 25.4N 86.1W Thu morning, 29.5N 84.5W Thu evening,
then move inland and weaken to a tropical storm near 34.3N 84.7W
Fri morning. Tropical Storm Helene will become an extratropical
cyclone near 36.7N 87.1W Fri evening and be over the southeastern
U.S. Sat morning. Swells generated by Helene will affect the
southern coast of Cuba and the Yucatan Peninsula of Mexico during
the next couple of days. Swells will spread northward toward the
west coast of Florida and the northeastern Gulf Coast later today
and Thursday. These swells are likely to cause life-threatening
surf and rip current conditions. The combination of a life-
threatening storm surge and the tide will cause normally dry areas
near the coast to be flooded by rising waters moving inland from
the shoreline. Hurricane Helene is expected to produce total rain
accumulations of 4 to 8 inches over western Cuba, the Cayman
Islands and the northeast Yucatan Peninsula, with isolated totals
around 12 inches. This rainfall brings a risk of considerable
flooding. Over portions of the Southeastern U.S. into the Southern
Appalachians, Helene is expected to produce total rain
accumulations of 6 to 12 inches with isolated totals around 18
inches. This rainfall will likely result in catastrophic and
potentially life-threatening flash and urban flooding, along with
significant river flooding. Numerous landslides are expected in
steep terrain across the southern Appalachians.

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

Invest 98L: Showers and thunderstorms have become slightly better
organized over the past 24 hours in association with a broad 1009
mb low pressure system along a tropical wave located several
hundred miles west of the Cabo Verde Islands. Scattered moderate
convection is observed from 13N to 18N between 32W and 41W. Seas
in these waters are 6-8 ft, with moderate to fresh E winds
observed along the northern periphery of the low and wave.
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 high chance of
tropical cyclone formation in the next 48 hours.

Please read the latest Tropical Weather Outlook issued by the National
Hurricane Center at hurricanes.gov

...TROPICAL WAVES...

A new tropical wave has recently emerged off the coast of Africa
and has its axis along 18W from 07N to 23N. Scattered moderate to
strong convection is occurring east of 23W from 11N to 18N.

A tropical wave approaching the Lesser Antilles has its axis along
55W from 20N southward, moving west at around 10 kts. Scattered
moderate convection is observed from 11N to 17N between 51W and
59W.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic near 18N16W and continues
westward to the 1009 mb low pressure (AL98) near 15N36W and then
southwestward to 09N42W. Scattered showers and isolated
thunderstorms are noted from 04N to 13N and east of 33W. The ITCZ
is analyzed from 08N43W to 05N53W.

A segment of the East Pacific monsoon trough is analyzed over the
far southwest Caribbean, and is aiding in the development of
scattered moderate convection along and near the trough axis.

...GULF OF MEXICO...

Please refer to the Special Features section above for details on
Hurricane Helene.

Aside from Helene, a generally dry airmass dominates the western
third of the Gulf of Mexico, except for a couple of showers and
isolated thunderstorms forming ahead of a cold front dropping into
the NW Gulf. Moderate or weaker winds and slight to moderate seas
are found in these waters.

For the forecast away from the immediate impacts from Hurricane
Helene, marine conditions will gradually improve across the Gulf
waters beginning on Fri or Fri night.

...CARIBBEAN SEA...

Please refer to the Special Features section above for details on
Hurricane Helene.

An upper-level inverted trough progressing through the area is
leading to the development of scattered showers and isolated
thunderstorms in portions of the central and eastern Caribbean.
Outside of the influence of Helene, moderate to fresh E trade
winds and seas of 3 to 5 ft are occurring in the central and
eastern Caribbean. Moderate or weaker winds and seas of 1 to 3 ft
are found in the eastern and SW Caribbean.

For the forecast, away from the immediate impacts from Hurricane
Helene, marine conditions will gradually improve across the basin
starting Thu night.

...ATLANTIC OCEAN...

Please refer to the Special Features section above for details on
Hurricane Helene and Invest 98L in the central Atlantic.

A surface trough in the north-central Atlantic results in
scattered showers north of 27N and between 46W and 57W. The
remainder of the Atlantic is under the influence of a broad 1022
mb high pressure system centered southwest of the Azores. The
pressure gradient between this ridge and lower pressures in the
deep tropics support fresh to locally strong NE winds from 19N to
26N and east of 30W. Seas in these waters are 4-7 ft. Moderate to
locally fresh southerly winds are present south of 10N and east
of 40W, along with seas of 4-7 ft. Elsewhere, moderate or weaker E
winds and moderate seas prevail.

For the forecast W of 55W and away from the immediate impacts from
Hurricane Helene, well NE of the area to the NE of Bermuda,
Tropical Storm Issac has formed this evening. Issac will move NE
further away from area waters, having no impact across the region.

$$
Adams