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Tropical Depression One-C Discussion Number   1
NWS Central Pacific Hurricane Center Honolulu HI   CP012025
Issued by NWS National Hurricane Center Miami FL
1100 PM HST Sat Jul 26 2025

Deep convection has persisted over the area of low pressure well 
southeast of the Hawaiian Islands for the last 12 hours or so, with 
the latest satellite images showing improved organization and a 
better defined banding structure.  The latest subjective Dvorak 
current intensity estimates came in at 2.0/30 knots from PHFO, 
1.5/25 knots from SAB, and 1.0/25 knots from JTWC.  A recent 
27/0620Z Metop-B ASCAT pass showed a well-defined low-level 
circulation with a large swath of 25-knot winds and a few embedded 
25- to 30-knot wind barbs.  Given the improved structure and 
organization of the system, advisories are being initiated on the 
first tropical cyclone of the season in the central Pacific, 
Tropical Depression One-C.  The initial intensity will be set at 30 
knots.

Tropical Depression One-C is moving toward the west, or 270 degrees, 
at 10 knots.  This general westward motion is expected to continue 
over the next couple of days as the system moves along the southern 
periphery of a subtropical ridge to the north.  Beyond 48 hours, the 
forward speed is expected to increase considerably in response to a 
low- to mid-level ridge strengthening to the north of cyclone.  The 
track forecast closely follows a blend of the TVCE and HCCA 
consensus guidance.

The environment will remain conducive for intensification over the 
next couple of days, as One-C remains over warm waters between 28 
and 29C, with adequate mid-level moisture and light to moderate 
easterly shear.  As a result, the intensity forecast calls for 
steady strengthening during this time, with One-C becoming Tropical 
Storm Iona on Sunday.  Beyond 60 hours, the cyclone will begin to 
experience increasing westerly vertical wind shear while also 
entraining drier mid-level air.  This is expected to lead to steady 
weakening, with the system becoming a tropical depression again 
around day 5.  The intensity forecast is best aligned with the HCCA 
intensity consensus guidance.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/0900Z 10.9N 145.6W   30 KT  35 MPH
 12H  27/1800Z 10.9N 146.7W   35 KT  40 MPH
 24H  28/0600Z 11.2N 148.2W   40 KT  45 MPH
 36H  28/1800Z 11.5N 150.0W   50 KT  60 MPH
 48H  29/0600Z 11.5N 152.2W   50 KT  60 MPH
 60H  29/1800Z 11.5N 154.8W   45 KT  50 MPH
 72H  30/0600Z 11.7N 157.7W   40 KT  45 MPH
 96H  31/0600Z 12.2N 164.7W   35 KT  40 MPH
120H  01/0600Z 12.9N 171.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Jelsema (CPHC)
 
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