WTPA35 PHFO 111759
TCPCP5

BULLETIN
HURRICANE HILDA INTERMEDIATE ADVISORY NUMBER 23A
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102015
800 AM HST TUE AUG 11 2015

…HILDA WEAKENING AND DRAWING CLOSER TO HAWAII…
…TROPICAL STORM WATCH REMAINS IN EFFECT FOR HAWAII COUNTY…

SUMMARY OF 800 AM HST…1800 UTC…INFORMATION
———————————————-
LOCATION…17.1N 151.5W
ABOUT 295 MI…475 KM ESE OF HILO HAWAII
ABOUT 510 MI…820 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS…75 MPH…120 KM/H
PRESENT MOVEMENT…NW OR 295 DEGREES AT 7 MPH…11 KM/H
MINIMUM CENTRAL PRESSURE…994 MB…29.35 INCHES

WATCHES AND WARNINGS
——————–
CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY…

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT…

A TROPICAL STORM WATCH IS IN EFFECT FOR…
* HAWAII COUNTY

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA…GENERALLY WITHIN 48 HOURS.

INTERESTS ELSEWHERE IN THE HAWAIIAN ISLANDS SHOULD CONTINUE TO
MONITOR THE PROGRESS OF HILDA.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA…PLEASE MONITOR
PRODUCTS ISSUED BY THE NATIONAL WEATHER SERVICE OFFICE IN
HONOLULU HAWAII.

DISCUSSION AND 48-HOUR OUTLOOK
——————————
AT 800 AM HST…1800 UTC…THE CENTER OF HURRICANE HILDA WAS LOCATED
NEAR LATITUDE 17.1 NORTH…LONGITUDE 151.5 WEST. HILDA IS MOVING
TOWARD THE WEST-NORTHWEST NEAR 7 MPH…11 KM/H…AND THIS GENERAL
MOTION IS EXPECTED TO CONTINUE INTO THURSDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 75 MPH…120 KM/H…WITH HIGHER
GUSTS. STEADY WEAKENING IS EXPECTED OVER THE NEXT 48 HOURS…WITH
HILDA FORECAST TO WEAKEN TO A TROPICAL STORM LATER TODAY.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 25 MILES…35 KM…FROM
THE CENTER…AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 70
MILES…110 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB…29.35 INCHES.

HAZARDS AFFECTING LAND
———————-
SURF…SWELLS ASSOCIATED WITH HURRICANE HILDA WILL PRODUCE LARGE
AND POTENTIALLY LIFE THREATENING SURF ALONG EAST AND SOUTHEAST
FACING SHORES OF PORTIONS OF THE HAWAIIAN ISLANDS OVER THE NEXT
COUPLE OF DAYS.

RAINFALL…HILDA IS EXPECTED TO PRODUCE VERY HEAVY RAIN OVER
PORTIONS OF THE HAWAIIAN ISLANDS FROM LATE WEDNESDAY INTO THE
WEEKEND. THESE RAINS COULD CAUSE LIFE THREATENING FLASH FLOODS AND
MUDSLIDES.

NEXT ADVISORY
————-
NEXT COMPLETE ADVISORY…1100 AM HST.

$$
FORECASTER JELSEMA/POWELL

WTPA45 PHFO 111453
TCDCP5

HURRICANE HILDA DISCUSSION NUMBER 23
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102015
500 AM HST TUE AUG 11 2015

HILDA CONTINUES TO WEAKEN IN THE FACE OF STRONG SOUTHWESTERLY
SHEAR…ANALYZED AS BEING NEAR 35 KT BY UW-CIMSS. LATEST SUBJECTIVE
DVORAK SATELLITE DATA-T VALUES FROM HFO/SAB/PGTW RANGE FROM 4.0/65
KT TO 4.5/77 KT…WHILE LATEST ADT VALUES ARE 4.4. BASED ON A
BLEND OF THESE ESTIMATES…AND A STEADILY DEGRADING SATELLITE
APPEARANCE…THE INITIAL INTENSITY FOR THIS ADVISORY HAS BEEN
LOWERED TO 75 KT.

THE INITIAL MOTION VECTOR FOR THIS ADVISORY IS A SOMEWHAT UNCERTAIN
315/06 KT…AS IT IS DIFFICULT TO DETERMINE EXACTLY WHERE THE
CENTER IS USING INFRARED IMAGERY…AND THERE HAVE NOT BEEN ANY
USABLE MICROWAVE PASSES OVER THE PAST 6 HOURS OR SO. ALTHOUGH THE
UPPER LEVEL FLOW OVER HILDA FEATURES RELATIVELY STRONG SOUTHWESTERLY
WINDS…THE CYCLONE IS CURRENTLY IN AN AREA OF LIGHT STEERING WINDS
BETWEEN A LOW ALOFT NORTH OF HAWAII…AND A HIGH TO THE DISTANT
EAST. THIS WILL INDUCE HILDA TO MOVE SLOWLY TOWARD THE NORTHWEST
THROUGH WEDNESDAY. THEREAFTER…HILDA IS EXPECTED TO MOVE A LITTLE
MORE QUICKLY TOWARD THE WEST…AS THE SHALLOW SYSTEM IS STEERED BY
THE LOW-LEVEL TRADE FLOW. THE OFFICIAL TRACK FORECAST IS ESSENTIALLY
AN UPDATE OF THE PREVIOUS…AND NOW LIES ON THE RIGHT HAND SIDE OF A
GUIDANCE ENVELOPE THAT HAS BEEN ANYTHING BUT CONSISTENT BETWEEN
MODEL RUNS.

HILDA IS LIVING ON BORROWED TIME…AND WILL SOON GIVE IN TO THE
HOSTILE ENVIRONMENT IN WHICH IT IS EMBEDDED. STRONG WESTERLY WINDS
ALOFT…ASSOCIATED WITH THE SUBTROPICAL JET…LIE ALONG THE
FORECAST PATH. THUS HILDA IS FORECAST TO STEADILY WEAKEN THROUGH THE
FORECAST PERIOD…WITH DISSIPATION FORECAST BY DAY 5. IN THE
MEANTIME HOWEVER…HILDA WILL APPROACH THE BIG ISLAND FROM THE
SOUTHEAST…AND UNCERTAINTIES ASSOCIATED WITH THE RATE OF WEAKENING
HAVE LED TO THE ISSUANCE OF A TROPICAL STORM WATCH FOR THE BIG
ISLAND WITH THIS PACKAGE. THE UPDATED INTENSITY FORECAST ALSO
CLOSELY FOLLOWS THE PREVIOUS…AND IS CLOSE TO SHIPS GUIDANCE
THROUGH 48 HOURS. THE RATE OF FORECAST WEAKENING THEREAFTER IS CLOSE
TO THE IVCN CONSENSUS…BUT SLOWER THAN SHIPS GUIDANCE.

WHILE UNCERTAINTY REMAINS AS TO THE EVENTUAL IMPACTS THAT MAY BE
FELT IN THE HAWAIIAN ISLANDS FROM HILDA…THE POTENTIAL FOR VERY
HEAVY RAINFALL APPEARS TO BE INCREASING. RECONNAISSANCE FLIGHTS INTO
HILDA WILL OCCUR AT 6 HOURLY INTERVALS STARTING THIS EVENING…WITH
THE NEXT MISSION SLATED FOR THIS MORNING.

FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 17.5N 151.3W 75 KT 85 MPH
12H 12/0000Z 17.9N 151.9W 65 KT 75 MPH
24H 12/1200Z 18.4N 152.6W 55 KT 65 MPH
36H 13/0000Z 18.8N 153.3W 45 KT 50 MPH
48H 13/1200Z 19.1N 154.4W 35 KT 40 MPH
72H 14/1200Z 19.4N 156.8W 30 KT 35 MPH
96H 15/1200Z 19.5N 159.5W 25 KT 30 MPH…POST-TROP/REMNT LOW
120H 16/1200Z…DISSIPATED

$$

FORECASTER BIRCHARD