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Hurricane Iona Discussion Number   9
NWS Central Pacific Hurricane Center Honolulu HI   CP012025
Issued by NWS National Hurricane Center Miami FL
1100 PM HST Mon Jul 28 2025
 
Iona has a very impressive satellite presentation this evening, with 
very cold cloud tops ranging from -70°C to -80°C surrounding the 
well-defined eye.  Subjective Dvorak current intensity estimates 
came in at 5.0/90 knots from PHFO and 5.5/102 knots from SAB.  The 
ADT and AiDT objective intensity estimates from UW-CIMSS have ranged 
between 97 and 104 knots over the past several hours. Based on a 
blend of these data, the initial intensity for this advisory has 
been increased to 100 knots, making Iona a Category 3 major
hurricane on the Saffir-Simpson hurricane wind scale.
 
Iona is moving due west, or 270 degrees at 11 knots. This general 
motion, along with a gradual increase in forward speed, is expected 
to continue over the next several days as the cyclone moves along 
the southern periphery of a subtropical ridge to the north.  A turn 
toward the west-northwest is anticipated by late in the week as the 
system is influenced by a weakness in the mid-level ridge, created 
by a developing upper-level low west of the International Date Line. 
The official track forecast remains near the center of the guidance 
envelope and is nearly identical to the previous advisory.  
Confidence remains high that Iona will stay well south of the 
Hawaiian Islands.
 
Environmental conditions appear conducive for further 
intensification during the next 12 hours or so, as Iona will remain 
over warm sea surface temperatures near 28C, with sufficient 
mid-level moisture and minimal vertical wind shear.  Given the 
conducive environment, the intensity forecast calls for Iona to 
reach category 4 status later tonight or early Tuesday.  Steady 
weakening is forecast to begin Tuesday night or Wednesday and 
continue into the weekend, as the system moves over slightly cooler 
waters, encounters increasing westerly vertical wind shear, and 
begins to entrain drier mid-level air.  The intensity forecast has 
been adjusted slightly upward from the previous advisory, reflecting 
the latest trends in the intensity guidance.  This aligns well with 
regional hurricane models during the next 24 to 36 hours, and then 
lies near or slightly below the intensity guidance envelope 
thereafter. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0900Z 10.8N 153.2W  100 KT 115 MPH
 12H  29/1800Z 10.8N 155.0W  115 KT 130 MPH
 24H  30/0600Z 10.8N 157.7W  110 KT 125 MPH
 36H  30/1800Z 11.0N 161.0W   95 KT 110 MPH
 48H  31/0600Z 11.3N 164.7W   80 KT  90 MPH
 60H  31/1800Z 11.8N 168.4W   70 KT  80 MPH
 72H  01/0600Z 12.6N 172.2W   60 KT  70 MPH
 96H  02/0600Z 14.3N 178.6W   50 KT  60 MPH
120H  03/0600Z 16.5N 176.1E   40 KT  45 MPH
 
$$
Forecaster Jelsema (CPHC)
 
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