930
WTPA41 PHFO 172059
TCDCP1
TROPICAL STORM CALVIN DISCUSSION NUMBER 25
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP032023
1100 AM HST MON JUL 17 2023
SATELLITE DATA SHOWED AN EXPOSED LOW-LEVEL CIRCULATION CENTER WITH
SPARSE DEEP CONVECTION ONLY IN THE OUTER RAINBAND WELL NORTH
OF THE CENTER. A US AIR FORCE RESERVE WC-130J FLEW ITS INITIAL
MISSION INTO CALVIN THIS MORNING. BASED ON A COMBINATION OF
THE FLIGHT LEVEL WINDS AND DROPSONDE DATA, MAXIMUM WINDS APPEAR
TO BE AROUND 45 KT IN THE NE QUAD AND WILL BE USED AS THE INITIAL
INTENSITY FOR THIS ADVISORY. THE SFMR DATA APPEARED TO BE TOO LOW.
THERE IS LITTLE CHANGE IN THE STEERING ENVIRONMENT. CALVIN
CONTINUES TO MOVE WESTWARD TO THE SOUTH OF A SUBTROPICAL RIDGE. THE
LATEST DYNAMICAL AIDS INDICATED THAT THIS STEERING WILL CONTINUE
OVER THE NEXT SEVERAL DAYS. THERE IS STILL SOME SPREAD IN THE
GUIDANCE FOR THE TRACK NEAR THE MAIN HAWAIIAN ISLANDS WITH HAFS-A
ON THE NORTH END AND CMC TO THE SOUTH. THE TRACK FORECAST IS CLOSE
TO THE PREVIOUS ADVISORY, BUT WITH A SLIGHT INCREASE IN FORWARD
SPEED. THE FORECAST IS ALSO VERY CLOSE TO HCCA. THIS PUTS THE CENTER
OF CALVIN NEAR OR OVER THE BIG ISLAND ON WEDNESDAY, WITH TROPICAL
STORM FORCE WINDS ARRIVING TUESDAY NIGHT.
THE SURROUNDING ENVIRONMENT AROUND CALVIN HAS BEEN DRY AND STABLE
WITH SSTS AROUND 24-25C. AS CALVIN MOVES WESTWARD, THE SSTS WILL
GRADUALLY INCREASE, WITH VALUES OF 26-27C AROUND THE MAIN HAWAIIAN
ISLANDS. AS A RESULT, DEEP CONVECTION MAY BECOME BETTER DEVELOPED,
WHICH IS SUGGESTED BY MODEL-SIMULATED SATELLITE IMAGERY FROM SOME
OF THE DYNAMICAL MODELS. THIS IS EXPECTED TO KEEP CALVIN AT
TROPICAL STORM INTENSITY BY THE TIME IT REACHES THE BIG ISLAND.
CALVIN WILL ALSO BE AFFECTED BY AN UPPER TROPOSPHERIC TROUGH IN
ABOUT 24-48 HRS. THE TROUGH WILL INCREASE THE VERTICAL SHEAR OVER
THE TROPICAL CYCLONE AND RESULT IN ITS ULTIMATE DEMISE.
KEY MESSAGES:
1. CALVIN IS FORECAST TO PASS VERY CLOSE TO THE BIG ISLAND TUESDAY
NIGHT AND WEDNESDAY, BRINGING A PERIOD OF HEAVY RAIN, HIGH SURF AND
LOCALLY STRONG WINDS. CALVIN IS EXPECTED TO WEAKEN AS IT MOVES
WESTWARD TO THE SOUTH OF THE OTHER HAWAIIAN ISLANDS WEDNESDAY AND
WEDNESDAY NIGHT, BRINGING THE POTENTIAL FOR SOME PERIPHERAL IMPACTS.
2. IT IS IMPORTANT TO NOT FOCUS ON THE EXACT FORECAST TRACK AND
INTENSITY WHEN PREPARING FOR CALVIN. PERSONS IN HAWAII COUNTY
SHOULD PREPARE FOR IMPACTS TODAY AND TUESDAY PRIOR TO THE ONSET OF
TROPICAL STORM FORCE WINDS. THESE IMPACTS COULD INCLUDE FLASH
FLOODING, DAMAGING WINDS, AND LARGE AND DANGEROUS SURF.
FORECAST POSITIONS AND MAX WINDS
INIT 17/2100Z 17.3N 143.3W 45 KT 50 MPH
12H 18/0600Z 17.4N 146.2W 40 KT 45 MPH
24H 18/1800Z 17.9N 149.9W 40 KT 45 MPH
36H 19/0600Z 18.3N 153.7W 40 KT 45 MPH
48H 19/1800Z 19.0N 157.5W 35 KT 40 MPH
60H 20/0600Z 19.5N 161.2W 30 KT 35 MPH
72H 20/1800Z 20.0N 165.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 21/1800Z...DISSIPATED
FORECASTER KODAMA
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