622
WTPA41 PHFO 181459
TCDCP1
TROPICAL STORM CALVIN DISCUSSION NUMBER 28
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP032023
500 AM HST TUE JUL 18 2023
A LARGE AREA OF THUNDERSTORMS CONTINUES TO EXPAND IN COVERAGE
NEAR THE PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OF
TROPICAL STORM CALVIN. AN AIRCRAFT FROM THE 53RD WEATHER
RECONNAISSANCE SQUADRON "HURRICANE HUNTERS" COMPLETED SAMPLING
CALVIN A FEW HOURS AGO. THEY FOUND WINDS AT FLIGHT-LEVEL AND FROM
DROPWINDSONDES THAT SUGGESTED THE PEAK SURFACE WIND SPEEDS WERE
CLOSE TO 40 KT. THE MOST RECENT SUBJECTIVE DVORAK SATELLITE
INTENSITY ESTIMATES WERE 35 KT FROM PHFO AND JTWC. THE LATEST CIMSS
SATCON INTENSITY ESTIMATE INDICATES 45 KT. THE INITIAL INTENSITY
FOR THIS ADVISORY IS MAINTAINED AT 40 KT BASED ON A BLEND OF THESE
ESTIMATES.
CALVIN'S INITIAL MOTION FOR THIS ADVISORY REMAINS 275/19 KT AS THE
CYCLONE CONTINUES TO BE STEERED RAPIDLY WESTWARD SOUTH OF A LARGE
SUBTROPICAL RIDGE. THIS STEERING IS EXPECTED TO CONTINUE OVER THE
NEXT 3 TO 4 DAYS. THE LATEST MODEL GUIDANCE, INCLUDING THE HCCA,
INDICATES THAT THE CENTER OF CALVIN WILL PASS OVER, OR JUST SOUTH
OF THE BIG ISLAND TONIGHT. THE LATEST TRACK FORECAST IS CLOSE TO
THE PREVIOUS FORECAST.
THE SURROUNDING ENVIRONMENT AROUND CALVIN CONTINUES TO BE SOMEWHAT
DRY AND STABLE. THE SSTS ARE GRADUALLY INCREASING TO AROUND 25C,
AND WE EXPECT ADDITIONAL WARMING OF THE SSTS TO 26-27C AS IT MOVES
CLOSER TO THE MAIN HAWAIIAN ISLANDS. THE HIGHER SSTS WILL LIKELY
SUPPORT ADDITIONAL DEEP CONVECTION SPREADING AROUND THE NORTHERN
SEMICIRCLE OF CALVIN AT LEAST INTO WEDNESDAY. THIS IS EXPECTED TO
KEEP THE CYCLONE AT TROPICAL STORM INTENSITY DURING THE NEXT 36
HOURS OR SO. AS A RESULT, A TROPICAL STORM WARNING REMAINS IN
EFFECT FOR HAWAII COUNTY. AFTER IT PASSES SOUTHWEST OF THE MAIN
HAWAIIAN ISLANDS, WE EXPECT CALVIN TO MOVE NEAR AN UPPER
TROPOSPHERIC TROUGH BY DAY 2. THIS FEATURE ALOFT WILL LIKELY
INCREASE THE VERTICAL WIND SHEAR OVER THE SYSTEM, AND WILL
EVENTUALLY RESULT IN IT BECOMING A POST-TROPICAL/REMNANT LOW BY
LATE THURSDAY. FINALLY, ANOTHER "HURRICANE HUNTER" AIRCRAFT IS
SCHEDULED TO FLY A SAMPLING MISSION INTO CALVIN A FEW HOURS AFTER
DAYBREAK THIS MORNING. THEY WILL MONITOR ANY SIGNIFICANT CHANGES
IN INTENSITY AND SIZE AS THE SYSTEM MOVES TOWARD THE BIG ISLAND.
KEY MESSAGES:
1. CALVIN IS FORECAST TO PASS OVER, OR VERY CLOSE TO HAWAII COUNTY
TONIGHT, 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 DURING DAYLIGHT HOURS FOR IMPACTS PRIOR TO THE
ONSET OF TROPICAL STORM CONDITIONS, WHICH ARE EXPECTED TO START
THIS EVENING. THESE IMPACTS COULD INCLUDE FLASH FLOODING, DAMAGING
WINDS, AND LARGE AND DANGEROUS SURF.
FORECAST POSITIONS AND MAX WINDS
INIT 18/1500Z 17.5N 149.5W 40 KT 45 MPH
12H 19/0000Z 17.9N 152.4W 40 KT 45 MPH
24H 19/1200Z 18.6N 156.1W 35 KT 40 MPH
36H 20/0000Z 19.1N 159.9W 35 KT 40 MPH
48H 20/1200Z 19.5N 163.6W 30 KT 35 MPH
60H 21/0000Z 19.6N 167.4W 25 KT 30 MPH
72H 21/1200Z 20.0N 171.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 22/1200Z...DISSIPATED
FORECASTER HOUSTON
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page