WTPA35 PHFO 102032
TCPCP5

BULLETIN
HURRICANE HILDA ADVISORY NUMBER 20
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102015
1100 AM HST MON AUG 10 2015

…HILDA CONTINUES TO TRACK WEST-NORTHWEST TOWARD HAWAII…

SUMMARY OF 1100 AM HST…2100 UTC…INFORMATION
———————————————–
LOCATION…16.3N 150.2W
ABOUT 400 MI…640 KM SE OF HILO HAWAII
ABOUT 610 MI…980 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS…90 MPH…150 KM/H
PRESENT MOVEMENT…WNW OR 300 DEGREES AT 8 MPH…13 KM/H
MINIMUM CENTRAL PRESSURE…976 MB…28.82 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 TONIGHT.

DISCUSSION AND 48-HOUR OUTLOOK
——————————
AT 1100 AM HST…2100 UTC…THE CENTER OF HURRICANE HILDA WAS
LOCATED NEAR LATITUDE 16.3 NORTH…LONGITUDE 150.2 WEST. HILDA IS
MOVING TOWARD THE WEST-NORTHWEST NEAR 8 MPH…13 KM/H…AND THIS
GENERAL MOTION IS EXPECTED WITH A DECREASE IN FORWARD SPEED 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 976 MB…28.82 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.

NEXT ADVISORY
————-
NEXT COMPLETE ADVISORY…500 PM HST.

$$
FORECASTER JELSEMA/DONALDSON

HFO-58006
WTPA45 PHFO 102113
TCDCP5

HURRICANE HILDA DISCUSSION NUMBER 20
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP102015
1100 AM HST MON AUG 10 2015

THE U.S. 53RD WEATHER RECONNAISSANCE AIRCRAFT WHICH SAMPLED THE
INNER CORE OF HILDA EARLIER THIS MORNING…INDICATED MAX SUSTAINED
WINDS FROM SFMR DATA OF 85 KNOTS. MEANWHILE…SURFACE WINDS FROM
THE MBL WIND DATA INDICATED 77 KNOTS…FROM THE WL150 DATA 74
KNOTS…AND FROM A REDUCTION OF THE MAX FLIGHT LEVEL WINDS RESULTED
IN SURFACE WINDS OF 82 KNOTS. BASED ON THE POTENTIAL OF SOME RAIN
CONTAMINATION IN THE SFMR WINDS…WE USED A BLENDED APPROACH FOR
THE INITIAL INTENSITY ESTIMATE. AS A RESULT…THE INITIAL INTENSITY
WAS KEPT AT 80 KNOTS FOR THIS ADVISORY. THE INITIAL MOTION IS
BASED ON THE AIRCRAFT FIXES AND SATELLITE EXTRAPOLATION…AND WILL
BE SET AT 300 DEGREES AT 7 KNOTS. THE SATELLITE PRESENTATION OF
HILDA CONTINUES TO SLOWLY DEGRADE AS THE SYSTEM ENCOUNTERS
INCREASING WESTERLY VERTICAL WIND SHEAR. THIS IS CONFIRMED BY THE
LATEST UW-CIMSS VERTICAL WIND SHEAR ANALYSIS WHICH SHOWS 36 KNOTS
FROM 260 DEGREES. MEANWHILE…THE LATEST FIXES FROM PHFO…SAB AND
JTWC INDICATED T NUMBERS OF 4.5 TO 5.0 OR 77 TO 90 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. WITH THE LOW ALOFT WELL TO THE NORTHWEST OF THE
SYSTEM EXPECTED TO RETROGRADE OFF TO THE NORTHWEST OVER THE NEXT
COUPLE DAYS…EXPECT THAT HILDA WILL CONTINUE TO TRACK SLOWLY OFF
TO THE WEST-NORTHWEST…WHICH IS SUPPORTED BY THE LATEST MODEL
CONSENSUS. THE MODEL GUIDANCE HAS INDICATED A SLOWING IN THE
FORWARD SPEED OF THE SYSTEM AS IT ENCOUNTERS INCREASING WESTERLY
WIND SHEAR OVER THE NEXT SEVERAL DAYS…AND THIS SEEMS REASONABLE AS
THE SYSTEM BECOMES INCREASINGLY TILTED AND LOSES DEEP CONVECTION. AS
A RESULT…THE FORECAST TRACK WILL REMAIN VERY CLOSE TO THE
PREVIOUS ADVISORY…WITH A SLOWING IN THE FORWARD SPEED OF THE
SYSTEM THROUGH 72 HOURS. THIS IS CLOSELY IN LINE WITH WITH THE
LATEST TVCN. BEYOND 72 HOURS…THE SHEAR IS EXPECTED TO HAVE TAKEN A
LARGE TOLL ON HILDA…WHICH SHOULD ALLOW IT TO GET INCREASINGLY
CAUGHT UP WITHIN THE TRADE WIND FLOW. AS A RESULT…WILL SHOW A
SLIGHT INCREASE IN FORWARD SPEED AND A SLIGHT BEND TOWARD THE LEFT
OR SOUTH OF THE PREVIOUS FORECAST TRACK FOR THE 96 AND 120 HOUR
POINTS.

THE INTENSITY FORECAST FOR HILDA WILL BE HIGHLY DEPENDENT ON THE
INCREASING WESTERLY WIND SHEAR OVER THE SYSTEM. THE COMBINATION OF
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. THE OFFICIAL INTENSITY
FORECAST IS VERY CLOSE TO ICON…AND WILL SHOW HILDA WEAKENING TO
TROPICAL STORM STRENGTH ON TUESDAY AND BECOMING A TROPICAL
DEPRESSION THURSDAY NIGHT OR FRIDAY.

FORECAST POSITIONS AND MAX WINDS

INIT 10/2100Z 16.3N 150.2W 80 KT 90 MPH
12H 11/0600Z 16.7N 150.8W 70 KT 80 MPH
24H 11/1800Z 17.2N 151.5W 60 KT 70 MPH
36H 12/0600Z 17.7N 152.2W 50 KT 60 MPH
48H 12/1800Z 18.1N 153.0W 45 KT 50 MPH
72H 13/1800Z 18.8N 154.8W 35 KT 40 MPH
96H 14/1800Z 19.4N 157.2W 30 KT 35 MPH
120H 15/1800Z 19.9N 160.1W 25 KT 30 MPH…POST-TROP/REMNT LOW

$$
FORECASTER JELSEMA/DONALDSON