WTPA35 PHFO 110237
TCPCP5

BULLETIN
HURRICANE HILDA ADVISORY NUMBER 21
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102015
500 PM HST MON AUG 10 2015

…HILDA CONTINUES TO TRACK NORTHWESTWARD TOWARD HAWAII…

SUMMARY OF 500 PM HST…0300 UTC…INFORMATION
———————————————-
LOCATION…16.7N 150.5W
ABOUT 365 MI…590 KM SE OF HILO HAWAII
ABOUT 580 MI…930 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS…90 MPH…150 KM/H
PRESENT MOVEMENT…NW OR 310 DEGREES AT 6 MPH…9 KM/H
MINIMUM CENTRAL PRESSURE…978 MB…28.88 INCHES

WATCHES AND WARNINGS
——————–
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

INTERESTS IN THE MAIN HAWAIIAN ISLANDS SHOULD CONTINUE TO MONITOR
THE PROGRESS OF HILDA. A TROPICAL STORM WATCH MAY BE REQUIRED FOR
THE BIG ISLAND AS EARLY AS TONIGHT.

DISCUSSION AND 48-HOUR OUTLOOK
——————————
AT 500 PM HST…0300 UTC…THE CENTER OF HURRICANE HILDA WAS LOCATED
NEAR LATITUDE 16.7 NORTH…LONGITUDE 150.5 WEST. HILDA IS MOVING
TOWARD THE NORTHWEST NEAR 6 MPH…9 KM/H…AND THIS GENERAL MOTION
IS EXPECTED OVER THE NEXT COUPLE OF DAYS.

MAXIMUM SUSTAINED WINDS ARE NEAR 90 MPH…150 KM/H…WITH HIGHER
GUSTS. STEADY WEAKENING IS EXPECTED OVER THE NEXT 48 HOURS…WITH
HILDA FORECAST TO WEAKEN TO A TROPICAL STORM ON TUESDAY.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 25 MILES…35 KM…FROM
THE CENTER…AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 90
MILES…150 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 978 MB…28.88 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 MAIN HAWAIIAN ISLANDS OVER THE NEXT
COUPLE OF DAYS.

RAINFALL…HILDA IS EXPECTED TO PRODUCE HEAVY RAIN OVER PORTIONS OF
THE STATE THURSDAY AND FRIDAY. THESE RAINS COULD CAUSE LIFE
THREATENING FLASH FLOODS AND MUDSLIDES.

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

$$
FORECASTER JELSEMA/DONALDSON



WTPA45 PHFO 110300
TCDCP5

HURRICANE HILDA DISCUSSION NUMBER 21
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102015
500 PM HST MON AUG 10 2015

DEEP CONVECTION CONTINUES TO FIRE OVER THE LOW LEVEL CIRCULATION
CENTER OF HILDA THIS AFTERNOON…WITH QUITE A BIT OF LIGHTNING
NOTED NEAR THE CENTER OF THE SYSTEM. AFTER APPEARING RATHER RAGGED
AROUND THE TIME OF THE PREVIOUS ADVISORY…THE SATELLITE
PRESENTATION HAS IMPROVED SIGNIFICANTLY OVER THE LAST COUPLE OF
HOURS DESPITE PERSISTENT STRONG WESTERLY VERTICAL WIND SHEAR. THE
LATEST UW-CIMSS VERTICAL WIND SHEAR ANALYSIS CONTINUES TO SUPPORT
THE IDEA OF A STRONGLY SHEARED ENVIRONMENT…DEPICTING 37 KNOTS FROM
260 DEGREES. THE LATEST FIXES FROM PHFO…SAB AND JTWC INDICATED T
NUMBERS OF 4.5 TO 5.0 OR 77 TO 90 KNOTS. BASED ON THE LATEST
FIXES…THE IMPROVEMENT IN THE SATELLITE PRESENTATION…AND DATA
FROM THE U.S. 53RD WEATHER RECONNAISSANCE AIRCRAFT WHICH SAMPLED THE
INNER CORE OF HILDA EARLIER THIS MORNING…THE INITIAL INTENSITY WAS
KEPT AT 80 KNOTS FOR THIS ADVISORY. THE INITIAL MOTION IS BASED ON A
COMBINATION OF THE SATELLITE FIXES…EARLIER AIRCRAFT FIXES AND
SATELLITE EXTRAPOLATION…AND WILL BE SET AT 310 DEGREES AT 5
KNOTS.

HILDA REMAINS WITHIN A WEAKNESS IN THE MID TO UPPER LEVEL RIDGE
EXTENDING FROM A LOW ALOFT NEAR 27N156W…SOUTHEASTWARD TO THE
TROPICAL CYCLONE. THE LOW ALOFT WELL TO THE NORTHWEST OF THE
SYSTEM IS EXPECTED TO RETROGRADE OFF TO THE NORTHWEST OVER THE NEXT
COUPLE OF DAYS. WITH VERTICAL WIND SHEAR VALUES REMAINING NEARLY
UNCHANGED THROUGH 48 HOURS…WE EXPECT THAT HILDA WILL CONTINUE
TO BE STEERED BY THE DEEP LAYER FLOW AND TRACK SLOWLY OFF TO THE
WEST-NORTHWEST. THIS IS IN LINE WITH THE MODEL CONSENSUS GUIDANCE
AND THE PREVIOUS OFFICIAL FORECAST. BEYOND 48 HOURS…THE WESTERLY
VERTICAL WIND SHEAR IS FORECAST TO INCREASE OVER THE SYSTEM…AND
THIS SHOULD ACT TO DISPLACE THE DEEP CONVECTION AND ALLOW HILDA TO
BECOME MORE INFLUENCED BY THE TRADE WIND FLOW. AS A RESULT…WILL
SHOW HILDA TRACKING WESTWARD BEYOND 48 HOURS…AND VERY CLOSE TO THE
PREVIOUS OFFICIAL FORECAST AS WELL.

THE INTENSITY FORECAST FOR HILDA WILL BE HIGHLY DEPENDENT ON THE
TIMING OF INCREASED WESTERLY VERTICAL WIND SHEAR OVER THE SYSTEM.
THE COMBINATION OF THE INCREASED SHEAR AND VERY DRY MID LEVEL AIR TO
THE WEST OF THE SYSTEM WHICH IS EVIDENT IN WATER VAPOR
IMAGERY…SHOULD ALLOW FOR SLOW AND STEADY WEAKENING THROUGH THE
FORECAST PERIOD. ADDITIONALLY…GIVEN THE SLOW MOTION OF THE
SYSTEM…THERE COULD BE SOME WEAKENING AS A RESULT OF UPWELLING OF
COLDER SUB SURFACE WATER. THE OFFICIAL INTENSITY FORECAST IS
VIRTUALLY UNCHANGED AND REMAINS VERY CLOSE TO ICON. THE FORECAST
SHOWS HILDA WEAKENING TO TROPICAL STORM STRENGTH ON TUESDAY AND
BECOMING A TROPICAL DEPRESSION THURSDAY NIGHT OR FRIDAY.

U.S AIR FORCE HURRICANE HUNTERS HAVE DEPARTED ON A MISSION TO FLY
THROUGH HILDA THIS EVENING. THE VALUABLE DATA FROM THIS MISSION
SHOULD HELP REFINE OUR FUTURE TRACK AND INTENSITY FORECASTS.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 16.7N 150.5W 80 KT 90 MPH
12H 11/1200Z 17.1N 151.0W 70 KT 80 MPH
24H 12/0000Z 17.6N 151.7W 60 KT 70 MPH
36H 12/1200Z 18.1N 152.3W 50 KT 60 MPH
48H 13/0000Z 18.4N 153.1W 45 KT 50 MPH
72H 14/0000Z 18.9N 154.7W 35 KT 40 MPH
96H 15/0000Z 19.3N 157.6W 30 KT 35 MPH
120H 16/0000Z 20.2N 160.7W 25 KT 30 MPH…POST-TROP/REMNT LOW

$$
FORECASTER JELSEMA/DONALDSON