Atlantic Basin Tropical Cyclones

Tropical Storm Ian Forecast Discussion


966 
WTNT44 KNHC 260300
TCDAT4

Tropical Storm Ian Discussion Number  12
NWS National Hurricane Center Miami FL       AL092022
1100 PM EDT Sun Sep 25 2022

The storm has become better organized-looking on satellite imagery, 
with strengthening central convection and developing banding 
features.  Upper-level anticyclonic outflow also appears to be 
increasing over the system.  Flight-level winds, Doppler radar 
velocities, and dropsonde data from a NOAA Hurricane Hunter aircraft 
indicate that Ian's intensity is now near 55 kt.

Ian has turned toward the northwest and the initial motion estimate
is now 315/11 kt.  During the next 48 hours, the tropical cyclone
is expected to turn toward the north as it moves along the western
side of a mid-level high pressure area.  Later in the forecast
period, a broad mid-tropospheric trough over the eastern United 
States is likely to induce a slightly east of northward motion.  
However, around 4 days, the steering currents are forecast to 
weaken as the trough moves to the east of Ian's longitude.  Some 
of the guidance model tracks such as that from the GFS have, again, 
shifted to the east, mainly after 48 hours.  The official track 
forecast has been shifted somewhat to the east of the previous one 
and is mainly a blend of the latest ECMWF and GFS predictions.  It 
should again be stressed that there is still significant 
uncertainty in the track of Ian, especially in the 3-5 day time 
frame.  Users should not focus on the details of the track forecast 
at longer time ranges.

Observations from the aircraft indicate that the tropical cyclone 
is developing an inner core, so significant intensification is 
likely to occur during the next couple of days.  The SHIPS Rapid 
Intensification Index indicate a fairly high chance for rapid 
strengthening during the next 24 to 36 hours, and the official 
forecast reflects this likelihood, calling for Ian to become a 
major hurricane over the southeastern Gulf of Mexico.


Key Messages:

1.  Ian is expected to produce heavy rainfall and instances of 
flash flooding and possible mudslides in areas of higher terrain, 
particularly over Jamaica and Cuba.  Considerable flooding impacts 
are possible later this week in west central Florida. Additional 
flash and urban flooding, and flooding on rivers across the Florida 
Peninsula and parts of the Southeast cannot be ruled out for later 
this week. 

2.  Life-threatening storm surge and hurricane-force winds are
expected in portions of western Cuba beginning late Monday, and Ian
is forecast to be at or near major hurricane strength when it is
near western Cuba. Efforts to protect life and property should be
rushed to completion.

3.  Ian is expected to be a major hurricane in the eastern Gulf of
Mexico during the middle of this week, but uncertainty in the track
and intensity forecasts remains higher than usual. Regardless of
Ian’s exact track and intensity, there is a risk of dangerous storm
surge, hurricane-force winds, and heavy rainfall along the west
coast of Florida and the Florida Panhandle by the middle of this
week, and residents in Florida 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  26/0300Z 17.3N  81.4W   55 KT  65 MPH
 12H  26/1200Z 18.7N  82.3W   65 KT  75 MPH
 24H  27/0000Z 20.8N  83.5W   85 KT 100 MPH
 36H  27/1200Z 22.7N  84.0W  100 KT 115 MPH
 48H  28/0000Z 24.7N  84.1W  105 KT 120 MPH
 60H  28/1200Z 26.2N  83.8W  115 KT 130 MPH
 72H  29/0000Z 27.6N  83.5W  105 KT 120 MPH
 96H  30/0000Z 29.0N  83.2W   80 KT  90 MPH
120H  01/0000Z 32.0N  82.5W   40 KT  45 MPH...INLAND

$$
Forecaster Pasch




Source link