[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 270258
TCDAT4

Hurricane Ian Discussion Number  16
NWS National Hurricane Center Miami FL       AL092022
1100 PM EDT Mon Sep 26 2022

Ian continues to become better organized on satellite images with
intense deep convection in its Central Dense Overcast and numerous
surrounding banding features.  The overall cloud pattern is quite
symmetric with well-defined upper-level outflow.  Observations from
both Air Force and NOAA Hurricane Hunter aircraft indicate that the
central pressure is falling, and the intensity is increased to 90
kt based on a recently reported 700 mb flight-level wind of 101 kt
from the Air Force plane.  This is also in agreement with a
subjective Dvorak satellite estimate from SAB.

Aside from its relatively brief time passing over western Cuba, Ian
will be moving over waters of very high oceanic heat content during
the next couple of days.  The various Rapid Intensification (RI)
indices show a significant probability of RI and this is reflected
in the short-term official intensity forecast.  However, the SHIPS
guidance, which is based on global model predictions, indicates that
a significant increase in southwesterly shear and a substantially
drying of low- to mid-level air will begin in 24-36 hours.  The NHC
forecast, like the previous one, shows strengthening to Category 4
intensity in a day or so, followed by 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 or
above the latest simple and corrected multi-model consensus
predictions.

Ian continues its north-northwestward trek at about 340/11 kt.  The
hurricane is expected to move north-northwestward to northward
over the southeastern Gulf of Mexico during the next day or so,
along the western periphery of a subtropical ridge.  After around
36 hours, the track forecast becomes more uncertain, since there is
considerable divergence of the track  models in the 2-3 day
time frame.  The guidance also shows considerable slowing of the
forward speed, due to a weakening of the steering currents, when
Ian approaches the west coast of Florida.  This slower forward
motion is likely to prolong the storm surge, wind, and rainfall
impacts, especially along the west coast of Florida.  The official
track forecast is adjusted just slightly east of the previous NHC
prediction based on the latest multi-model consensus aid, TVCN.


Key Messages:

1. Life-threatening storm surge, hurricane-force winds, flash floods
and possible mudslides are expected in portions of western Cuba
beginning overnight and continuing into Tuesday. Devastating wind
damage is possible where the core of Ian moves across western Cuba.
Efforts to protect life and property should be rushed to completion.

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 Tuesday.

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 and northern Florida
Wednesday and Thursday and the Southeast by Friday and Saturday,
potentially causing flash, urban and small stream flooding.
Considerable flooding, including significant, prolonged river
flooding, is likely across Central Florida.


FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 21.3N  83.4W   90 KT 105 MPH
 12H  27/1200Z 22.8N  83.7W  105 KT 120 MPH
 24H  28/0000Z 24.5N  83.7W  120 KT 140 MPH
 36H  28/1200Z 26.1N  83.5W  115 KT 130 MPH
 48H  29/0000Z 27.2N  83.1W  105 KT 120 MPH
 60H  29/1200Z 27.9N  82.7W   95 KT 110 MPH...INLAND
 72H  30/0000Z 28.6N  82.4W   65 KT  75 MPH...INLAND
 96H  01/0000Z 31.3N  82.2W   30 KT  35 MPH...INLAND
120H  02/0000Z 35.0N  81.5W   25 KT  30 MPH...INLAND

$$
Forecaster Pasch
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