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Tropical Storm Iona Discussion Number  22
NWS Central Pacific Hurricane Center Honolulu HI   CP012025
Issued by NWS National Hurricane Center Miami FL
500 AM HST Fri Aug 01 2025
 
Satellite imagery shows that the convection associated with Iona 
remains fragmented and disorganized.  Scatterometer data received 
since the last advisory indicates the maximum winds are near 35 kt 
and that the circulation has weakened to the point that it is 
uncertain whether it is still closed. The system will be maintained 
as a 35-kt tropical storm for this advisory.
 
The initial motion is estimated at 285/18 kt. As mentioned 
previously, Iona is expected to continue moving west-northwestward 
over the next couple of days with a gradual decrease in forward 
speed as it moves along the southern periphery of the subtropical 
ridge to the north. A turn toward the northwest is forecast after 
36-48 h as the system approaches a developing break in the ridge. 
The new forecast track lies near the consensus models and the center 
of the guidance envelope, and it is an update of the previous 
forecast.

Iona continues to be affected by westerly shear, which should 
persist for the next 12-18 h. After that, the system is forecast to 
interact with an upper-level trough, and it will likely enter an 
area of upper-level convergence by 60-72 h.  Based on this scenario 
and the dynamical guidance, the new intensity forecast calls for 
Iona remain a tropical storm for 36 h or so, followed by weakening 
to a depression by 48 h and degenerating into a trough by 96 h.  
Given the current state of organization and the generally 
unfavorable environment, the system could weaken to a trough at any 
time during the next 72 h.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/1500Z 14.6N 176.3W   35 KT  40 MPH
 12H  02/0000Z 15.4N 178.5W   35 KT  40 MPH
 24H  02/1200Z 16.6N 178.8E   35 KT  40 MPH
 36H  03/0000Z 17.8N 176.5E   35 KT  40 MPH
 48H  03/1200Z 19.0N 174.3E   30 KT  35 MPH
 60H  04/0000Z 20.6N 172.1E   30 KT  35 MPH
 72H  04/1200Z 22.5N 170.2E   30 KT  35 MPH
 96H  05/1200Z...DISSIPATED
 
$$
Forecaster Beven
 
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