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Tropical Storm Iona Discussion Number  16
NWS Central Pacific Hurricane Center Honolulu HI   CP012025
Issued by NWS National Hurricane Center Miami FL
500 PM HST Wed Jul 30 2025
 
Iona continues to weaken, with the low-level circulation center 
remaining mostly exposed. Recent satellite imagery showed a 
convective burst on the north side of the center, with cloud tops 
reaching as cold as -75°C. However, this burst has not been 
sustained, and convection remains generally disorganized. An earlier 
ASCAT pass sampled peak winds of around 40 kt in the northern 
semicircle of the circulation. Subjective and objective satellite 
intensity estimates remain in the 40–65 kt range. Taking into 
account the degraded satellite presentation, ASCAT data, and the 
blend of available intensity estimates, the initial intensity is set 
at 45 kt.
 
The initial motion is 275/20 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 so
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 36 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.

The weakening trend appears to have stabilized, with only slight 
additional weakening expected tonight. By Thursday, Iona's intensity 
is forecast to level off as it moves over warmer sea surface 
temperatures and into a marginally more favorable atmospheric 
environment. The system is expected to resume weakening by early 
next week as it encounters mid-level dry air and increasing vertical 
shear. The intensity forecast has been adjusted slightly downward to 
reflect the recent trends. This forecast assumes that Iona will 
maintain enough convection to remain a tropical cyclone. Should 
convection fail to persist, the system could degenerate into a 
remnant low or trough before day five.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0300Z 11.8N 164.8W   45 KT  50 MPH
 12H  31/1200Z 12.2N 167.7W   40 KT  45 MPH
 24H  01/0000Z 12.8N 171.3W   35 KT  40 MPH
 36H  01/1200Z 13.4N 174.8W   35 KT  40 MPH
 48H  02/0000Z 14.2N 177.7W   35 KT  40 MPH
 60H  02/1200Z 15.0N 179.6E   35 KT  40 MPH
 72H  03/0000Z 16.0N 177.3E   35 KT  40 MPH
 96H  04/0000Z 18.2N 172.6E   35 KT  40 MPH
120H  05/0000Z 20.6N 168.1E   30 KT  35 MPH
 
$$
Forecaster Gibbs (CPHC)
 
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