[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 291005
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Tue Aug 29 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 0600 UTC surface analysis and satellite imagery through
0700 UTC.

Major Hurricane Franklin is centered near 30.2N 70.8W at 29/0900
UTC or 330 nm WSW of Bermuda, moving NNE at 8 kt. Estimated
minimum central pressure is 935 mb. Maximum sustained wind speed
is 120 kt with gusts to 145 kt. Peak seas are currently up to 37
ft. Numerous moderate to strong convection is noted within 90 nm
of the center with numerous moderate elsewhere within 180 nm in
the E semicircle and 120 nm in the W semicircle. A north-
northeastward to northeastward motion with a faster forward
speed is expected during the next few days. On the forecast
track, the center of Franklin is expected to pass well to the
northwest of Bermuda on Wednesday. Franklin is still a
formidable category 4 hurricane on the Saffir-Simpson Hurricane
Wind Scale. Steady weakening is forecast during the next several
days. Life-threatening surf and rip currents generated by
Franklin are already affecting Bermuda and the coast of the
southeast United States. These conditions are expected to spread
northward along the east coast of the United States and Atlantic
Canada later today into Wednesday. 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
Franklin NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

Recently upgraded Hurricane Idalia is centered near 23.1N 85.0W
at 29/0900 UTC or 70 nm N of the western tip of Cuba, moving N
at 12 kt. Estimated minimum central pressure is 981 mb. Maximum
sustained wind speed is 65 kt with gusts to 80 kt. Peak seas are
currently around 19-21 ft with an altimeter pass just off the
coast of western Cuba just E of Cabo Corrientes, indicating seas
to 23 ft which is not out of the realm of possibility given the
long fetch in SW flow into the coast. Numerous moderate to
strong convection is evident within 90 nm in the NE semicircle
and 45 nm in the SW semicircle, with scattered moderate
convection elsewhere within 25.5N84.5W to 23N81W to 14N85.5W to
14N91W.  A northward motion is expected today, followed by a
faster north-northeast motion later today and Wednesday.  On the
forecast track, the center of Idalia is forecast to move over
the eastern Gulf of Mexico today, reach the Gulf coast of
Florida within the Hurricane Warning area on Wednesday, and move
close to the Carolina coastline on Thursday. Rapid
intensification is likely through landfall, and Idalia is
forecast to become an extremely dangerous major hurricane before
landfall on Wednesday. Heavy rainfall is expected across
portions of western Cuba and may produce areas of flash and
urban flooding as well as landslides. Areas of flash and urban
flooding, some of which may be locally significant, are expected
across portions of the west coast of Florida, the Florida
Panhandle, and southern Georgia beginning today into Wednesday,
spreading into portions of the eastern Carolinas Wednesday into
Thursday. 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
Idalia NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

...TROPICAL WAVES...

A tropical wave is emerging off the coast of Africa near 17W/18W.
Scattered moderate isolated strong convection is evident from 07N
to 19N between the coast of Africa and 21W. Environmental conditions
appear marginally conducive for gradual development of this
system, and a tropical depression could form later in the week
while the system moves west-northwestward to northwestward across
the eastern tropical Atlantic.

A tropical wave is in the Atlantic Ocean along 43W, from 18N
southward, moving W at around 20 kt. No significant convection is
evident with this tropical wave.

A tropical wave is in the Atlantic Ocean approaching the Leeward
Islands along 60W, from 17N southward to along the border of
Guyana and Venezuela, moving W around 20 kt. Scattered moderate
isolated strong convection is evident from 10N to 15N between 52W
and 60W.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coastal borders
of Mauritania near 19N16W to 10N30W to 07N45W. All nearby
convection is described in the Tropical Waves section above.

...GULF OF MEXICO...

Please read the SPECIAL FEATURES section for details about
Tropical Storm Idalia whose center is N of the western tip of
Cuba.

Weak anticyclonic flow in the western Gulf with cyclonic flow
associated with Idalia dominating the remainder of the basin.
Gentle to moderate winds dominate the waters away from Idalia.
Seas are 1-3 ft in the Gulf W of 91W and also N of 28N with the
remainder of the basin dominated by seas generated by Idalia.

For the forecast, Idalia will move to 24.9N 84.8W this afternoon,
27.8N 84.3W Wed morning, inland to 30.6N 82.9W Wed afternoon,
move inland and weaken to a tropical storm near 32.7N 80.5W Thu
morning, 33.8N 77.5W Thu afternoon, and 33.9N 74.4W Fri morning.
Idalia will change little in intensity as it moves to 33.3N 71.5W
early Sat. High pressure and improving conditions will arrive in
the wake of Idalia late in the week.

...CARIBBEAN SEA...

Please read the SPECIAL FEATURES section for details about
Tropical Storm Idalia whose center is N of the western tip of
Cuba.

Refer to the Tropical Waves section above for details on a
tropical wave approaching the Leeward Islands.

High pressure ridging extends from E to W just N of the basin
along 23N with moderate to fresh E-SE winds dominating the
Caribbean away from the influence of Idalia, except light to
gentle in the SW Caribbean. Seas are mainly 4-7 ft outside the
influence of Idalia, except for 1-2 ft in the SW Caribbean.

For the forecast, Idalia will move to 24.9N 84.8W this afternoon,
then continuing N away from the NW Caribbean to 27.8N 84.3W Wed
morning. Meanwhile, high pressure will build westward across the
western Atlantic through Thu as Hurricane Franklin lifts north of
the region. This will lead to moderate to fresh trade winds in the
eastern Caribbean by tonight, then in the central Caribbean by
Tue, locally strong there.

...ATLANTIC OCEAN...

Please read the SPECIAL FEATURES section for details about Major
Hurricane Franklin, and on Tropical Storm Idalia in the far SE
Gulf of Mexico forecast to impact the waters off the SE United
States.

A 1016 mb low pressure (reopened invest AL92) is evident near
28N51.5W. Scattered moderate isolated strong convection is evident
from 26N to 29N between 49W and 53W. Associated winds are mainly
moderate to fresh, but up to strong in the deep convection per
earlier ASCAT altimeter data. Recent satellite wind data also
indicates that its circulation has become better defined.
Environmental conditions appear favorable for additional
development over the next couple of days before becoming more
unfavorable by the latter part of this week as the system drifts
slowly over the central subtropical Atlantic.

Scattered moderate isolated strong convection is evident from 21N
to 28N between 57W and 62W due to the influence of a mid to upper
level feature.

Away from the influence of Franklin, gentle to moderate winds
dominate the open waters to the SW N Atlantic. The only exception
is N of 18N and E of 30W where fresh to strong NE winds are
offshore northern Africa due to a persistent tight pressure
gradient over the region. Seas are 6-10 ft in that area. Seas are
3-6 ft across the remainder of the open waters.

For the forecast, Franklin will move N of the area to 31.3N 70.3W
this afternoon, 33.0N 68.8W Wed morning, then to 34.8N 66.3W Wed
afternoon when all associated conditions begin to lift N of 31N.
Meanwhile, Idalia will move to 24.9N 84.8W this afternoon, 27.8N
84.3W Wed morning, inland to 30.6N 82.9W Wed afternoon, move
inland and weaken to a tropical storm near 32.7N 80.5W Thu
morning, 33.8N 77.5W Thu afternoon, and 33.9N 74.4W Fri morning.
Idalia will change little in intensity as it moves to 33.3N 71.5W
early Sat. Expect increasing winds and building seas E of Florida
beginning late tonight as Idalia moves across the Eastern Gulf of
Mexico.

$$
Lewitsky
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