[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 270858
TCDAT4

Hurricane Ian Discussion Number  17
NWS National Hurricane Center Miami FL       AL092022
500 AM EDT Tue Sep 27 2022

Ian's satellite presentation continued to improve up until the
center reached the coast of western Cuba around 0830 UTC.  An Air
Force Reserve reconnaissance aircraft that was in the storm until
around 0400 UTC reported peak 700-mb flight-level winds of 101 kt,
and a peak SFMR wind of 97 kt. During the final pass through the
center, dropsonde data supported a minimum pressure of 960 mb.
Given the continued improvement in satellite imagery, Dvorak data
T-numbers from SAB and TAFB of T5.5 (102 kt), and objective
estimates from UW/CIMSS of T5.4 (100 kt), the intensity was
increased to 100 kt shortly after 0600 UTC.  The latest objective
Dvorak estimates have increased to around 110 kt, and that is the
estimated landfall intensity and initial intensity for this
advisory.  NOAA and Air Force Reserve reconnaissance aircraft are
scheduled to investigate the storm as it moves off the northern
coast of Cuba this morning.

Ian is expected to spend only spend a few hours over western Cuba,
and little overall change in strength is likely during that time.
The center should emerge over the southeastern Gulf of Mexico later
this morning, where warm water and generally low vertical wind shear
conditions are expected to allow for additional intensification, and
the NHC forecast calls for Ian to reach category 4 strength.  By 24
to 36 hours, increasing southwesterly vertical wind shear and drier
mid-level air are likely to result in some gradual weakening.
However, Ian is still expected to be a major hurricane when it
reaches the Florida west coast.  The official intensity forecast is
near the latest simple and corrected multi-model consensus
predictions.

Ian has turned northward and is moving 355/10 kt. The hurricane
should continue on a northward motion today around the western
periphery of a subtropical ridge.  After that time, a broad trough
over the eastern United States is expected to cause a
north-northeastward turn.  There continues to be larger-than-normal
spread in the track guidance by 36-48 hours, however the trend in
the global models has been more southward and eastward over the
last cycle or two.  As a result, the NHC track has been adjusted to
the southeast of the previous forecast and it lies just west of the
TVCA multi-model consensus aid.  Users are reminded to not focus on
the exact track as some additional adjustments to the track are
possible, and wind, storm surge, and rainfall hazards will extend
far from the center.  The updated forecast track has necessitated
several changes to the warnings and watches across the Florida Keys
and Florida peninsula, including an extension of the Hurricane
Warning southward to Bonita Beach on the west coast.

Key Messages:

1. Life-threatening storm surge, hurricane-force winds, flash
floods and possible mudslides are expected in portions of western
Cuba today. Devastating wind damage is expected where the core of
Ian moves across western Cuba this morning.

2. There is a danger of life-threatening storm surge along much
of the Florida west coast where a storm surge warning has been
issued, with the highest risk from Fort Myers to the Tampa Bay
region.  Residents in these areas should listen to advice given by
local officials.

3. Hurricane-force winds are expected in the hurricane warning area
in west-central Florida beginning Wednesday morning with tropical
storm conditions expected by late today.

4. Heavy rainfall will spread across western Cuba through Tuesday.
This will likely produce instances of flash flooding and possible
mudslides in areas of higher terrain over western Cuba.

5. Heavy rainfall will increase across the Florida Keys and South
Florida Tuesday, spreading into central to northern Florida
Wednesday and Thursday, and the Southeast by Friday and Saturday,
likely causing flash, urban, and small stream flooding.
Considerable flooding is expected across Central Florida into
southern Georgia  and coastal South Carolina, with significant,
prolonged river flooding expected across central to northern
Florida.


FORECAST POSITIONS AND MAX WINDS

INIT  27/0900Z 22.3N  83.7W  110 KT 125 MPH
 12H  27/1800Z 23.7N  83.7W  120 KT 140 MPH
 24H  28/0600Z 25.4N  83.5W  115 KT 130 MPH
 36H  28/1800Z 26.7N  83.1W  110 KT 125 MPH
 48H  29/0600Z 27.6N  82.6W  105 KT 120 MPH
 60H  29/1800Z 28.3N  82.2W   75 KT  85 MPH...INLAND
 72H  30/0600Z 29.0N  82.0W   55 KT  65 MPH...INLAND
 96H  01/0600Z 31.7N  82.2W   30 KT  35 MPH...INLAND
120H  02/0600Z 35.0N  82.0W   25 KT  30 MPH...INLAND

$$
Forecaster Brown/Latto
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