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Hurricane Ian Forecast Discussion


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WTNT44 KNHC 280904
TCDAT4

Hurricane Ian Discussion Number  22
NWS National Hurricane Center Miami FL       AL092022
500 AM EDT Wed Sep 28 2022

Ian completed an eyewall replacement cycle during the overnight 
hours, and very recent data from an Air Force Reserve Hurricane 
Hunter aircraft indicate that the hurricane has reached category 4 
intensity.  The plane reported that the central pressure has fallen 
to 942 mb, down about 10 mb from around midnight.  The plane 
measured a peak 700-mb flight-level wind of 141 kt, and an SFMR 
wind of 109 kt.  A blend of the 700-mb reduced wind and the SFMR 
yields an initial intensity of 120 kt.  Although there is some 
moderate shear over the hurricane, this is not likely to affect Ian 
very much due to its large size. Some fluctuations in intensity are 
possible before the center reaches the coast later today, but Ian is 
expected to reach the coast as an extremely dangerous category 4 
hurricane.  Weakening is expected while Ian moves over the Florida 
peninsula. 

Ian has jogged a little to the left this morning, but the
longer-term motion remains north-northeastward or 015 degrees
at 9 kt.  The hurricane should continue moving north-northeastward
through Thursday between the western side of a subtropical ridge
and a broad trough over the eastern United States. This motion is
expected to bring the center of Ian onshore along the west coast of
Florida later today, and over central Florida tonight and Thursday. 
A shortwave trough that is forecast to move southward toward the
northwestern Gulf in about 24 to 36 hours is expected to sharpen
the trough over the eastern U.S. causing Ian to turn northward
along coast of northeastern Florida and Georgia Thursday night and
Friday.  The model envelope did not change much this cycle, and very
little cross-track adjustments were needed to the official
forecast.  The GFS and ECWMF are noticeably slower than the 
remainder of the dynamical models, and the updated NHC track 
forecast is a little slower than the previous advisory and slightly 
slower than the TVCA consensus aid out of respect for those models.


Key Messages:

1. Life-threatening storm surge is expected along the Florida west
coast and the Lower Florida Keys where a storm surge warning is
in effect, with the highest risk from Naples to the Sarasota region.
Residents in these areas should listen to advice given by local
officials and follow any evacuation orders for your area.

2. Hurricane-force winds are expected in the hurricane warning 
area in southwest and west-central Florida beginning Wednesday 
morning with tropical storm conditions expected overnight.  
Catastrophic wind damage is expected near the core of Ian when it 
moves onshore. 

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

FORECAST POSITIONS AND MAX WINDS

INIT  28/0900Z 25.6N  82.9W  120 KT 140 MPH
 12H  28/1800Z 26.7N  82.4W  120 KT 140 MPH
 24H  29/0600Z 27.7N  81.8W   70 KT  80 MPH...INLAND
 36H  29/1800Z 28.7N  81.1W   50 KT  60 MPH...INLAND
 48H  30/0600Z 29.8N  80.7W   45 KT  50 MPH...OVER WATER
 60H  30/1800Z 31.6N  80.8W   45 KT  50 MPH
 72H  01/0600Z 33.6N  81.4W   30 KT  35 MPH...INLAND
 96H  02/0600Z 36.1N  82.1W   25 KT  30 MPH...POST-TROP/INLAND
120H  03/0600Z...DISSIPATED

$$
Forecaster Brown



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