424
WTPA41 PHFO 191449
TCDCP1
TROPICAL STORM CALVIN DISCUSSION NUMBER 32
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP032023
500 AM HST WED JUL 19 2023
DEEP CONVECTION AROUND CALVIN COLLAPSED OVERNIGHT, LEAVING RESIDUAL
DEEP CONVECTION ACROSS EAST AND SOUTHEAST-FACING SHORES AND
SLOPES OF THE BIG ISLAND AND MAUI. THIS IS THE RESULT OF DEEP
TROPICAL FLOW INTERACTING WITH TERRAIN. CALVIN'S LOW LEVEL
CIRCULATION CENTER (LLCC) HAS BECOME COMPLETELY EXPOSED, ALLOWING
SMALL CORRECTIONS IN INITIAL POSITION AND MOVEMENT FOR THIS
ADVISORY. INSTRUMENTS ABOARD THE US AIR FORCE RESERVE'S HURRICANE
HUNTER AIRCRAFT SHOWED MAXIMUM FLIGHT LEVEL WINDS OF 47 KT, REDUCED
TO ABOUT 42 KT AT SEA LEVEL. SUBJECTIVE DVORAK SATELLITE ANALYSES
FROM PHFO AND JTWC GAVE CURRENT INTENSITY NUMBERS OF 2.5, 35 KT AND
2.0, 30 KT, RESPECTIVELY. UW-CIMSS DERIVED AN ADT INTENSITY OF
37 KT, WHILE AN ASCAT PASS FROM LAST EVENING SHOWED MAXIMUM WINDS
OF ABOUT 40 KT WITHIN CALVIN'S NORTHEAST QUADRANT. BASED ON THESE
DATA, THE INITIAL INTENSITY FOR THIS ADVISORY HAS BEEN DECREASED TO
40 KT.
THE INITIAL MOTION FOR THIS ADVISORY IS UNCHANGED AT 275/17 KT AS
CALVIN CONTINUES TO MOVE SOUTH OF A LARGE SUBTROPICAL RIDGE. NO
SIGNIFICANT CHANGE IN THIS STEERING IS EXPECTED OVER THE NEXT
SEVERAL DAYS. CALVIN IS ABOUT TO COMPLETE ITS PASSAGE SOUTH OF THE
BIG ISLAND AND THE FORECAST TRACK IS ESSENTIALLY THE SAME AS THE
PREVIOUS FORECAST TRACK, ASIDE FROM SMALL CHANGES IN INITIAL
POSITION AND FORWARD SPEED FROM TAU 12 AND BEYOND. THE TOTAL TRACK
IS SHORTER AS THIS SYSTEM IS FORECAST TO DISSIPATE AT TAU 60. THE
FORECAST TRACK REMAINS WITHIN, BUT ON THE SOUTHERN SIDE, OF THE
GUIDANCE ENVELOPE. ALTHOUGH THE CENTER OF CALVIN IS PASSING SOUTH OF
THE BIG ISLAND, MUCH OF THE ISLAND REMAINS WITHIN THE 34 KT RADIUS,
AND IMPACTS FROM STRONG WINDS, HEAVY RAINFALL, AND HIGH SURF ARE
OCCURRING.
THE FORECAST CALLS FOR CALVIN TO FINISH ITS PASSAGE SOUTH OF THE
BIG ISLAND THIS MORNING, THEN CONTINUE MOVING WESTWARD AWAY FROM
THE MAIN ISLAND CHAIN AS A WEAKENING TROPICAL STORM. VERTICAL SHEAR
AFFECTING THE TROPICAL CYCLONE IS EXPECTED TO BE MODERATE TODAY,
THEN STRONG BY TONIGHT. THE STRONG SHEAR SHOULD RESULT IN
WEAKENING TO POST-TROPICAL/REMNANT LOW STATUS LATE THURSDAY NIGHT.
KEY MESSAGES:
1. CALVIN HAS ALMOST COMPLETED ITS PASSAGE SOUTH OF HAWAII COUNTY.
EXPECT PERIODS OF FLASH FLOODING, DANGEROUS SURF AND DAMAGING
WINDS. CALVIN WILL CONTINUE TO WEAKEN AS IT MOVES WESTWARD TO THE
SOUTH OF THE OTHER HAWAIIAN ISLANDS TODAY AND TONIGHT, BRINGING THE
POTENTIAL FOR SOME PERIPHERAL IMPACTS.
FORECAST POSITIONS AND MAX WINDS
INIT 19/1500Z 17.8N 156.8W 40 KT 45 MPH
12H 20/0000Z 17.9N 159.5W 35 KT 40 MPH
24H 20/1200Z 18.1N 163.1W 35 KT 40 MPH
36H 21/0000Z 18.2N 166.8W 30 KT 35 MPH
48H 21/1200Z 18.2N 170.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 22/0000Z...DISSIPATED
FORECASTER POWELL
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