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Tropical Storm Iona Discussion Number  23
NWS Central Pacific Hurricane Center Honolulu HI   CP012025
Issued by NWS National Hurricane Center Miami FL
1100 AM HST Fri Aug 01 2025
 
Convection associated with Iona remains disorganized, with clusters 
of convection now occurring only in the southern semicircle.  While 
satellite imagery shows that the circulation is becoming elongated, 
it is still uncertain whether it is actually closed. An upcoming 
scatterometer overpass should help provide more information on 
whether the circulation still exists and on the maximum winds. For 
the time being, the initial intensity is held at 35 kt as a blend 
of the objective and subjective satellite intensity estimates. 
 
The initial motion is now at 285/16 kt. Iona is expected to move 
west-northwestward during the next couple of days with a gradual 
decrease in forward speed 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 west of 165E.  The track guidance has shifted a little 
to the west on this cycle, and the new forecast track is slightly 
to the west of the previous track.
 
The intensity forecast scenario is unchanged from earlier. 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 intensity forecast calls for Iona 
remain a tropical storm for 12 h or so, followed by weakening to a 
depression by 24 h and degenerating into a remnant low by 72 h.
Given the current state of organization and the generally 
unfavorable environment, there remains the possibility the system 
could weaken to a trough at any time during the next 60-72 h.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/2100Z 15.0N 177.6W   35 KT  40 MPH
 12H  02/0600Z 15.8N 179.6W   35 KT  40 MPH
 24H  02/1800Z 17.0N 177.8E   30 KT  35 MPH
 36H  03/0600Z 18.2N 175.5E   30 KT  35 MPH
 48H  03/1800Z 19.4N 173.4E   30 KT  35 MPH
 60H  04/0600Z 21.1N 171.3E   30 KT  35 MPH
 72H  04/1800Z 22.7N 169.5E   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  05/1800Z...DISSIPATED
 
$$
Forecaster Beven
 
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