540
WTPA45 PHFO 231444
TCDCP5
HURRICANE OLAF DISCUSSION NUMBER 35
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP192015
500 AM HST FRI OCT 23 2015
A RAGGED 10 NM WIDE EYE EMBEDDED WITHIN AN ASYMMETRIC DEEP
CONVECTIVE RING DESCRIBES THE CENTRAL FEATURE FOR OLAF. SOME
ADDITIONAL BANDING WITHIN THE NORTH AND EAST QUADRANTS GIVES US THE
IMPRESSION THAT OLAF ORGANIZATION HAS IMPROVED SLIGHTLY SINCE LAST
EVENING. SUBJECTIVE DVORAK SATELLITE INTENSITY ESTIMATES ARE
UNCHANGED FROM EARLIER...5.5...102 KT...FROM ALL THREE SATELLITE
CENTERS. HOWEVER...UW-CIMSS ADT INCREASED DRAMATICALLY TO AN
UNREPRESENTATIVE 6.7...132 KT. GIVEN THE SLIGHTLY BETTER OVERALL
SATELLITE PRESENTATION...AND AS A NOD TO THE ADT TREND...WE WILL
ASSIGN 105 KT AS THE INITIAL INTENSITY FOR THIS ADVISORY.
INITIAL MOTION IS JUST EAST OF DUE NORTH...OR 005/08 KT...AS OLAF
CONTINUES MOVING INTO A WEAKNESS IN THE SUBTROPICAL RIDGE FAR
NORTHEAST OF THE MAIN HAWAIIAN ISLANDS. A LARGE NORTHWARD COMPONENT
WILL CONTINUE THROUGH THE FORECAST PERIOD...WITH A PAIR OF TROUGHS
PASSING EASTWARD TO THE NORTH OF OLAF NUDGING THIS SYSTEM EVER MORE
INSISTENTLY TO THE EAST THROUGH DAY FOUR. TRACK GUIDANCE HAS CHANGE
VERY LITTLE THROUGH 96 HOURS. HOWEVER...GFS JOINED ECMWF IN
DEPICTING A SUDDEN SWING TO THE NORTHWEST BETWEEN 96 AND 120
HOURS...DRAGGING CONSENSUS LEFTWARD LATE IN THE FORECAST PERIOD AS
WELL. THIS MAY BE DUE TO BOTH GLOBAL MODELS SEEING A DECAPITATED
OLAF SUDDENLY COMING UNDER THE INFLUENCE OF SHALLOW LOW LEVEL FLOW
ALONG THE SOUTH FLANK OF THE SUBTROPICAL RIDGE AT THAT POINT.
HOWEVER...BOTH GFS AND ECMWF KEEP OLAF RATHER STRONG ON DAYS FOUR
AND FIVE...SO PERHAPS RIDGE STRENGTHENING TO THE NORTH OF OLAF IS
SEEN. EITHER WAY...THE DAY FIVE FORECAST POINT WAS ADJUSTED TO THE
LEFT TO ACCOUNT FOR THIS EFFECT...LEAVING THE REMAINING FORECAST
POINTS PRETTY MUCH INTACT FROM LAST TIME.
SHIPS AND UW-CIMSS CONTINUE TO DISAGREE ON THE AMOUNT OF SHEAR
ACROSS OLAF...RANGING FROM 15 TO 25 KT...RESPECTIVELY. WE ASSUME
THAT THE AMOUNT OF SHEAR PRESENT IS CLOSER TO THE LOWER VALUE SINCE
THE INNER CORE OF OLAF APPEARS TO BE UNAFFECTED. INTENSITY GUIDANCE
SHOWS WEAKENING ACROSS THE BOARD THROUGH THE NEXT FIVE DAYS AS SHEAR
INCREASES AND SSTS DROP...WITH SHIPS DISSIPATING OLAF BY DAY FOUR.
THE GLOBAL MODELS WEAKEN OLAF MUCH MORE SLOWLY...WITH GFS DEPICTING
OLAF STILL AT TROPICAL STORM STRENGTH ON DAY FIVE. WE WILL KEEP THE
SAME STEADY WEAKENING TREND FROM LAST TIME...EXCEPT FOR A BUMP UP TO
95 KT AT 24 HOURS TO ACCOUNT FOR THE INITIAL INTENSITY INCREASE. WE
FORECAST OLAF WILL REMAIN A MINIMAL HURRICANE AT 72 HOURS...THEN
WEAKEN TO A TROPICAL STORM AT 96 AND 120 HOURS.
FORECAST POSITIONS AND MAX WINDS
INIT 23/1500Z 15.9N 146.2W 105 KT 120 MPH
12H 24/0000Z 16.9N 145.9W 100 KT 115 MPH
24H 24/1200Z 18.3N 145.5W 95 KT 110 MPH
36H 25/0000Z 19.5N 144.9W 90 KT 105 MPH
48H 25/1200Z 20.7N 144.1W 85 KT 100 MPH
72H 26/1200Z 23.3N 141.8W 65 KT 75 MPH
96H 27/1200Z 25.8N 137.9W 60 KT 70 MPH
120H 28/1200Z 30.3N 138.0W 45 KT 50 MPH
$$
FORECASTER POWELL
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