[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 261457
TCDAT4

Hurricane Ian Discussion Number  14
NWS National Hurricane Center Miami FL       AL092022
1100 AM EDT Mon Sep 26 2022

The satellite presentation of Ian has improved this morning. Deep
convection has increased within the inner core during the past
several hours, with an expanding central dense overcast noted in
recent satellite imagery. The inner core structure continues to take
shape in radar data, although the eyewall still has a banded
appearance and remains open on the west side. Dropsonde data from
the NOAA and Air Force Hurricane Hunter aircraft indicate that the
minimum pressure has gradually fallen to about 980 mb, and the
initial intensity is raised slightly to 70 kt for this advisory.

The intensity of Ian has increased by 30 kt during the past 18 h.
Further rapid intensification (RI) is expected during the next 24-36
h as Ian crosses the high oceanic heat content of the northwestern
Caribbean Sea within a very low vertical wind shear (VWS)
environment. The latest SHIPS-RI probabilities continue to highlight
the high likelihood of this scenario, with a 73 percent chance of a
35-kt wind speed increase in 24 h and a 79 percent chance of a 45-kt
increase in 36 h. The NHC intensity forecast is similar to the
previous one, and it shows Ian becoming a major hurricane by the
time it reaches western Cuba. Ian is forecast to reach its peak
intensity in 36 h over the southeastern Gulf of Mexico. Then,
increasing southwesterly shear by 36-48 h is expected to bring an
end to the intensification phase. The combination of strong VWS and
drier mid-level air will induce weakening thereafter, but Ian is
expected to remain at or near major hurricane strength as it passes
near the west-central coast of Florida on Wednesday and Thursday.

Ian continues to move northwestward at 325/11 kt. A turn toward the
north-northwest and north is expected during the next day or so as
the hurricane moves around the western extent of a mid-level ridge.
Then, an upper-level trough over the eastern U.S. should cause Ian
to turn more north-northeastward through Thursday. This track brings
the center of Ian close to the west-central coast of Florida during
the middle of the week. An even greater concern is the slower
forward motion that is forecast during this period, as the upper
trough passes north and east of Ian and the steering currents
weaken. This would likely prolong the storm surge, wind, and
rainfall impacts along the affected portions of the west coast of
Florida, although the roughly shore-parallel track still makes it
difficult to pinpoint exactly what locations will experience the
most severe impacts. The track guidance has come into better
agreement during the first 72 h of the forecast period, and only a
minor eastward adjustment was made to the NHC track forecast in line
with the multi-model consensus aids.

The aircraft data indicate that the 34-kt wind radii in the
northeastern quadrant were 20-30 n mi larger than previously
estimated, and this has been reflected in the latest forecast.
Based on these changes, Tropical Storm Watches have been issued for
the middle Florida Keys and extended southward along the
southwestern coast of Florida.


Key Messages:

1. Life-threatening storm surge, hurricane-force winds, flash
floods and possible mudslides are expected in portions of western
Cuba beginning this evening 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. Life-threatening storm surge is possible along much of the
Florida west coast, 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 possible in the hurricane watch area
in west-central Florida beginning Wednesday morning with tropical
storm conditions possible by late Tuesday.  Residents in this area
should ensure that they have their hurricane plan in place.

4. Heavy rainfall will increase across the Florida Keys and south
Florida Tuesday, spreading to central and northern Florida Wednesday
and Thursday, potentially causing flash, urban and small stream
flooding. Significant prolonged river flooding is likely across
central Florida.



FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 19.1N  82.7W   70 KT  80 MPH
 12H  27/0000Z 20.7N  83.5W   90 KT 105 MPH
 24H  27/1200Z 22.7N  84.0W  105 KT 120 MPH
 36H  28/0000Z 24.5N  84.0W  120 KT 140 MPH
 48H  28/1200Z 26.1N  83.8W  120 KT 140 MPH
 60H  29/0000Z 27.2N  83.5W  105 KT 120 MPH
 72H  29/1200Z 28.0N  83.2W   90 KT 105 MPH
 96H  30/1200Z 29.8N  82.9W   55 KT  65 MPH...INLAND
120H  01/1200Z 32.8N  82.6W   30 KT  35 MPH...INLAND

$$
Forecaster Reinhart
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