490
WTPA41 PHFO 012036
TCDCP1
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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