ZCZC HFOTCDCP1 ALL
TTAA00 PHFO DDHHMM
 
Tropical Storm Iona Discussion Number  15
NWS Central Pacific Hurricane Center Honolulu HI   CP012025
Issued by NWS National Hurricane Center Miami FL
1100 AM HST Wed Jul 30 2025
 
Iona continues to rapidly weaken, as the low-level center is now 
seen in visible imagery exposed well to the west-northwest of the 
remaining poorly-organized convection.  Subjective and objective 
satellite intensity estimates again have decreased significantly 
and currently are in the 40-65 kt range. Based on a blend of these 
estimates, the initial intensity is reduced to a possibly generous 
55 kt, and Iona is downgraded to a tropical storm.
 
The initial motion is 275/19 kt. There is little change in the 
forecast philosophy from the past couple of forecasts, as a general 
westward motion is expected to continue during the next day or two 
while Iona moves along the southern periphery of a low- to mid-level
subtropical ridge to the north.  A turn toward the west-northwest
and a gradual decrease in forward speed are expected after 48 h as 
the system is steered into a weakness in the ridge.  There has been 
little change in the forecast guidance since the last advisory, and 
the new forecast track is similar to the previous track.

Rapid weakening should continue for the next 12 h or so due to
westerly vertical shear and a track over cooler sea surface 
temperatures.  After that, the intensity forecast shows a period of 
little change in strength as sea surface temperatures begin to warm 
along the forecast track and the atmospheric conditions become a 
little more favorable. After 72 h, Iona should again weaken as it 
encounters mid-level dry air and another bout of vertical shear.  
The intensity forecast was again lowered below the previous 
forecast based on the current intensity trends.  Note that the 
intensity forecast is based on the premise that Iona will re-develop 
enough convection to sustain the system as a tropical cyclone. If 
this does not happen, the cyclone could degenerate to a remnant low 
or trough before 120 h.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/2100Z 11.7N 162.6W   55 KT  65 MPH
 12H  31/0600Z 12.1N 165.5W   45 KT  50 MPH
 24H  31/1800Z 12.7N 169.3W   40 KT  45 MPH
 36H  01/0600Z 13.4N 172.7W   40 KT  45 MPH
 48H  01/1800Z 14.1N 175.9W   40 KT  45 MPH
 60H  02/0600Z 15.1N 178.8W   40 KT  45 MPH
 72H  02/1800Z 16.0N 178.7E   40 KT  45 MPH
 96H  03/1800Z 18.1N 174.1E   35 KT  40 MPH
120H  04/1800Z 20.2N 169.1E   30 KT  35 MPH
 
$$
Forecaster Beven
 
NNNN