[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 271500
TCDAT4

Hurricane Ian Discussion Number  18
NWS National Hurricane Center Miami FL       AL092022
1100 AM EDT Tue Sep 27 2022

The well-defined eye of Ian emerged off the coast of western Cuba
about an hour ago.  Earlier reports from the NOAA Hurricane Hunter
aircraft indicate that Ian strengthened up through landfall, with an
estimated pressure of 947 mb over western Cuba.  While the hurricane
has filled somewhat due to the passage over Cuba, Air Force Reserve
and NOAA Hurricane Hunter data show that it has grown in size.  The
initial wind speed is set to 100 kt.

Ian is moving northward, or 005/9 kt. Dropsonde data from the NOAA
G-IV aircraft indicate a potent upper-level trough is over the
western Gulf of Mexico.  The strength of this trough, the associated
southwesterly flow, and the vertical depth of Ian appear to be the
keys to the forecast.  There has been a notable trend toward the
hurricane remaining more intact up through landfall, meaning Ian is
likely to turn to the northeast and not move as slowly as previously
anticipated.  However, it should be emphasized that this track
remains very uncertain, with a typical spread in the steering
features leading to big speed and track differences down the line,
not to mention the oblique angle of approach to Florida.  The latest
forecast is adjusted to the southeast for this advisory, showing
landfall 6-12 hours faster than before, and we will have to see if
the southern trend continues in the afternoon guidance.  The rest of
the forecast after landfall has been adjusted to the northeast as
well, though it is still slower than the consensus guidance at
longer range.

The hurricane should remain in a favorable environment for
restrengthening over the next day or so while it moves over the warm
waters of the southeastern Gulf of Mexico and in light-shear
conditions.  While the shear should increase by tomorrow, it isn't
expected to be enough to significantly weaken the hurricane before
landfall.  Model guidance is in fairly good agreement on this
scenario, and the NHC intensity forecast continues to call for an
extremely dangerous hurricane landfall for southwestern Florida.

The new forecast necessitates a Hurricane Watch for portions of
extreme southwestern Florida, and a Tropical Storm Watch for the
rest of southeastern Florida that wasn't previously under a watch.
Users are reminded to not focus on the exact track as some
additional adjustments to the track are possible. Significant wind,
storm surge, and rainfall hazards will extend far from the center.


Key Messages:

1. Life-threatening storm surge, hurricane-force winds, flash floods
and possible mudslides are expected to continue in portions of
western Cuba today. Devastating wind damage is expected near the
core of Ian.

2. Life-threatening storm surge looks increasingly likely along much
of the Florida west coast where a storm surge warning is in effect,
with the highest risk from Fort Myers to the Tampa Bay region.
Residents in these areas should listen to advice given by local
officials and follow evacuation orders if made for your area.

3. Hurricane-force winds are expected in the hurricane warning area
in southwest and west-central Florida beginning Wednesday morning
with tropical storm conditions expected by this evening.  Residents
should rush all preparations to completion today.

4. Heavy rainfall will increase across the Florida Keys and south
Florida today, spreading into central and northern Florida tonight
and Wednesday, into the Southeast U.S.  by Thursday and Friday,
likely causing flash, urban, and small stream flooding. Considerable
flooding is expected across central Florida into southern Georgia
and coastal South Carolina, with widespread, prolonged moderate to
major river flooding expected across central Florida.


FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 23.0N  83.5W  100 KT 115 MPH
 12H  28/0000Z 24.4N  83.3W  115 KT 130 MPH
 24H  28/1200Z 26.0N  83.0W  115 KT 130 MPH
 36H  29/0000Z 27.1N  82.5W  110 KT 125 MPH
 48H  29/1200Z 27.8N  82.1W   75 KT  85 MPH...INLAND
 60H  30/0000Z 28.5N  81.7W   60 KT  70 MPH...INLAND
 72H  30/1200Z 29.5N  81.5W   50 KT  60 MPH...INLAND
 96H  01/1200Z 33.0N  81.8W   35 KT  40 MPH...INLAND
120H  02/1200Z 35.0N  81.5W   25 KT  30 MPH...POST-TROP/EXTRATROP

$$
Forecaster Blake
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