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Tropical Storm Ian Forecast Discussion


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WTNT44 KNHC 241454
TCDAT4

Tropical Storm Ian Discussion Number   6
NWS National Hurricane Center Miami FL       AL092022
1100 AM EDT Sat Sep 24 2022

Ian still has an asymmetric appearance in satellite imagery this 
morning, with most of the deep convection located over the western 
portion of the circulation. Tail Doppler radar and dropsonde data 
from a NOAA Hurricane Hunter aircraft indicate the cyclone is still 
vertically tilted, with the low- to mid-level center displaced to 
the south of the surface center. This structure is likely a product 
of the northerly shear that has affected the cyclone since genesis. 
The aircraft reported 700-mb flight-level winds of 43 kt and SFMR 
retrievals slightly above 35 kt, which supports keeping the initial 
intensity at 40 kt for this advisory.

The initial motion is a bit south of due west at 260/13 kt. A 
generally westward motion is expected through tonight as the cyclone 
is steered by a narrow ridge to its north. Ian is forecast to turn 
northwestward on Sunday and north-northwestward on Monday as it 
moves across the northwestern Caribbean Sea around the periphery of 
the ridge. The NHC track forecast during this period has been 
adjusted slightly south and west of the previous one, in line with 
the track consensus aids. Beyond 72 h, there is still a large amount 
of cross-track spread in the guidance as Ian emerges into the 
eastern Gulf of Mexico and approaches Florida. Hopefully, data 
collected from special radiosonde releases beginning later today and 
a scheduled NOAA G-IV flight will help resolve the steering flow 
around Ian and deep-layer trough that is forecast to be over the 
eastern U.S. early next week. The guidance envelope has once again 
shifted westward this cycle, and the official NHC track forecast has 
been adjusted in this direction as well, though it still lies 
slightly to the east of the TVCA and HCCA aids. Further adjustments 
to the track forecast may be needed given the increased uncertainty 
in the day 3-5 period. 

Ian is moving into a lower shear environment over very warm waters, 
and it should not take long for the system to shed its tilted 
structure and develop an inner core. Once that occurs, significant 
to rapid intensification is expected while Ian crosses the 
northwestern Caribbean Sea. The intensity guidance unanimously 
supports strengthening during the next several days, and the 
SHIPS-RII probabilities indicate a 67 percent chance of a 65-kt 
intensity increase in 72 h. Therefore, the NHC track forecast has 
been raised from the previous one, showing Ian becoming a hurricane 
by late Sunday and approaching western Cuba at or near major 
hurricane strength by Monday night. Limited land interaction is 
expected as the cyclone quickly passes over western Cuba, and Ian 
is forecast to be a major hurricane over the eastern Gulf of Mexico 
on Tuesday and Wednesday as it approaches the west coast of Florida.

Key Messages:

1.  Ian is expected to produce heavy rainfall, flash flooding, and 
possible mudslides in areas of higher terrain, particularly over 
Jamaica and Cuba. Limited flash and urban flooding is possible with 
rainfall across the Florida Keys and Florida peninsula through mid 
next week.

2.  Hurricane conditions are possible in the Cayman Islands by early 
Monday, with tropical storm conditions possible by late Sunday.  
Tropical storm conditions are possible in Jamaica on
Sunday.

3.  Ian is forecast to move near or over western Cuba and approach 
the west coast of the Florida peninsula at or near major hurricane 
strength early next week, where there is increasing confidence in 
multiple life-threatening hazards: storm surge, hurricane-force 
winds and rainfall flooding. While it is too soon to determine the 
exact magnitude and location of these hazards, residents in Cuba, 
the Florida Keys, and the Florida peninsula should ensure they have 
their hurricane plan in place, follow any advice given by local 
officials, and closely monitor updates to the forecast. 

FORECAST POSITIONS AND MAX WINDS

INIT  24/1500Z 14.4N  75.2W   40 KT  45 MPH
 12H  25/0000Z 14.5N  76.8W   45 KT  50 MPH
 24H  25/1200Z 15.5N  78.9W   55 KT  65 MPH
 36H  26/0000Z 17.0N  80.7W   70 KT  80 MPH
 48H  26/1200Z 18.8N  82.3W   85 KT 100 MPH
 60H  27/0000Z 20.7N  83.4W   95 KT 110 MPH
 72H  27/1200Z 22.7N  84.1W  100 KT 115 MPH
 96H  28/1200Z 26.0N  83.9W  105 KT 120 MPH
120H  29/1200Z 28.6N  82.9W   95 KT 110 MPH

$$
Forecaster Reinhart



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