252
WTPA41 PHFO 011438
TCDCP1
TROPICAL STORM IONA DISCUSSION NUMBER 22
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP012025
ISSUED BY NWS NATIONAL HURRICANE CENTER MIAMI FL
500 AM HST FRI AUG 01 2025
SATELLITE IMAGERY SHOWS THAT THE CONVECTION ASSOCIATED WITH IONA
REMAINS FRAGMENTED AND DISORGANIZED. SCATTEROMETER DATA RECEIVED
SINCE THE LAST ADVISORY INDICATES THE MAXIMUM WINDS ARE NEAR 35 KT
AND THAT THE CIRCULATION HAS WEAKENED TO THE POINT THAT IT IS
UNCERTAIN WHETHER IT IS STILL CLOSED. THE SYSTEM WILL BE MAINTAINED
AS A 35-KT TROPICAL STORM FOR THIS ADVISORY.
THE INITIAL MOTION IS ESTIMATED AT 285/18 KT. AS MENTIONED
PREVIOUSLY, IONA IS EXPECTED TO CONTINUE MOVING WEST-NORTHWESTWARD
OVER THE NEXT COUPLE OF DAYS WITH A GRADUAL DECREASE IN FORWARD
SPEED AS IT MOVES 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.
THE NEW FORECAST TRACK LIES NEAR THE CONSENSUS MODELS AND THE CENTER
OF THE GUIDANCE ENVELOPE, AND IT IS AN UPDATE OF THE PREVIOUS
FORECAST.
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 NEW INTENSITY FORECAST CALLS FOR
IONA REMAIN A TROPICAL STORM FOR 36 H OR SO, FOLLOWED BY WEAKENING
TO A DEPRESSION BY 48 H AND DEGENERATING INTO A TROUGH BY 96 H.
GIVEN THE CURRENT STATE OF ORGANIZATION AND THE GENERALLY
UNFAVORABLE ENVIRONMENT, THE SYSTEM COULD WEAKEN TO A TROUGH AT ANY
TIME DURING THE NEXT 72 H.
FORECAST POSITIONS AND MAX WINDS
INIT 01/1500Z 14.6N 176.3W 35 KT 40 MPH
12H 02/0000Z 15.4N 178.5W 35 KT 40 MPH
24H 02/1200Z 16.6N 178.8E 35 KT 40 MPH
36H 03/0000Z 17.8N 176.5E 35 KT 40 MPH
48H 03/1200Z 19.0N 174.3E 30 KT 35 MPH
60H 04/0000Z 20.6N 172.1E 30 KT 35 MPH
72H 04/1200Z 22.5N 170.2E 30 KT 35 MPH
96H 05/1200Z...DISSIPATED
FORECASTER BEVEN
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