[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 282058
TCDAT4

Hurricane Ian Discussion Number  25
NWS National Hurricane Center Miami FL       AL092022
500 PM EDT Wed Sep 28 2022

An Air Force Reserve Hurricane Hunter aircraft provided the last
fix on Ian just before the hurricane made landfall at Cayo Costa,
Florida, with the landfall time near at 305 pm EDT.  The
minimum pressure had risen to about 940 mb at landfall, suggesting
that the winds had come down slightly, and the landfall intensity
was estimated near 130 kt.  While there hasn't been much in situ
data recently, satellite images show that the eye has become more
cloud filled, and Tampa Doppler radar data is indicating a gradual
reduction in winds.  The initial intensity is set to 120 kt on this
advisory.

Further weakening is forecast while Ian moves over central Florida
during the next day and emerges into the western Atlantic later on
Thursday.  While there is a lot of vertical wind shear in the
environment there, a favorable trough interaction from a trough in
the southern United States is expected to counteract the shear,
resulting in Ian staying a strong tropical storm through landfall
on the southeast U.S. coast.  Little change was made to the
intensity forecast, which is near or somewhat above the consensus
guidance.

The hurricane is moving to the north-northeast at about 8 kt.  The
aforementioned trough is likely to cause Ian to turn northward over
the western Atlantic and to the north-northwest by the weekend.
Model guidance is just a bit faster to the north-northeast than the
last cycle, and the new forecast is nudged in that direction.  The
trough will probably cause Ian to transition to an extratropical
cyclone in a few days over the southeastern United States, and this
new forecast reflects this likelihood.


Key Messages:

1. Catastrophic storm surge inundation of 12 to 18 feet above ground
level along with destructive waves is ongoing along the southwest
Florida coastline from Englewood to Bonita Beach, including
Charlotte Harbor.

2. Catastrophic wind damage is occurring along the southwestern
coast of Florida in areas near the eyewall of Ian. Hurricane-force
winds, especially in gusts, are expected to spread inland to central
Florida near the core of Ian through early Thursday. Hurricane
conditions are expected along the east-central Florida coast
overnight through early Thursday.

3. Heavy rainfall will spread across the Florida peninsula through
Thursday and reach portions of the Southeast U.S. later this week
and this weekend.  Widespread, life-threatening catastrophic
flooding, with major to record river flooding, are expected to
continue across portions of central Florida with considerable
flooding in northern Florida, southeastern Georgia and eastern South
Carolina.

4.  There is a danger of life-threatening storm surge on Thursday
and Friday along the coasts of northeast Florida, Georgia, and South
Carolina, with hurricane conditions possible. Residents in these
areas should follow any advice given by local officials.


FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 26.9N  82.0W  120 KT 140 MPH...INLAND
 12H  29/0600Z 27.8N  81.6W   75 KT  85 MPH...INLAND
 24H  29/1800Z 28.8N  81.0W   55 KT  65 MPH...INLAND
 36H  30/0600Z 30.0N  80.6W   55 KT  65 MPH...OVER WATER
 48H  30/1800Z 31.9N  80.6W   55 KT  65 MPH...OVER WATER
 60H  01/0600Z 34.0N  81.0W   40 KT  45 MPH...INLAND
 72H  01/1800Z 36.0N  81.5W   20 KT  25 MPH...POST-TROP/EXTRATROP
 96H  02/1800Z...DISSIPATED

$$
Forecaster Blake
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