WTPA45 PHFO 201500 TCDCP5 HURRICANE OLAF DISCUSSION NUMBER 23 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP192015 500 AM HST TUE OCT 20 2015 THE SATELLITE PRESENTATION OF OLAF HAS CHANGED LITTLE SINCE THE PREVIOUS ADVISORY...WITH A 10 TO 15 NM WIDE EYE SURROUNDED BY A RING OF DEEP CONVECTION THAT HAS BEEN FLUCTUATING IN INTENSITY. THIS RING REMAINS SUFFICIENTLY COLD...AND THE EYE SUFFICIENTLY WARM...TO YIELD A DVORAK INTENSITY ESTIMATE OF 6.5/127 KT. THIS IS SUPPORTED BY PHFO...SAB AND UW-CIMSS ADT AND SATCON ANALYSES...AND AN INITIAL INTENSITY OF 130 KT WILL BE MAINTAINED FOR THIS ADVISORY. THE INITIAL MOTION VECTOR FOR THIS ADVISORY...285/09 KT...IS EXACTLY AS IT WAS EARLIER...WITH OLAF SOUTH OF A DEEP-LAYER RIDGE THAT IS EXPECTED TO CHANGE LITTLE THROUGH TONIGHT. ONCE AGAIN...LITTLE CHANGE TO THE ONGOING TRACK PHILOSOPHY IS PRESENTED BY THE LATEST ROUND OF GUIDANCE. OLAF IS FORECAST TO TURN TOWARD THE NORTHWEST ON WEDNESDAY...AS THE RIDGE WEAKENS IN RESPONSE TO A SHORTWAVE TROUGH PASSING TO ITS NORTH. ANOTHER PASSING SHORTWAVE WILL KEEP THE RIDGE WEAK ON THURSDAY...WITH OLAF THEN MOVING TOWARD THE NORTH-NORTHWEST BETWEEN 145W AND 150W LONGITUDE INTO FRIDAY. THIS TREND OF TURNING TO THE RIGHT WILL CONTINUE THROUGH THE FORECAST PERIOD...WITH AN EVEN SHARPER SHORTWAVE TROUGH INDUCING A TURN TOWARD THE NORTHEAST ON DAY 5. THE RELIABLE TRACK MODELS REMAIN TIGHTLY CLUSTERED THROUGH THE FORECAST PERIOD AS THEY HAVE FOR THE PAST COUPLE OF CYCLES...LEADING TO INCREASED CONFIDENCE THAT OLAF WILL REMAIN WELL EAST OF THE HAWAIIAN ISLANDS. THE UPDATED OFFICIAL FORECAST TRACK AGAIN LIES VERY CLOSE TO THE PREVIOUS ADVISORY TRACK...AND IS NEAR THE GFEX AND TVCN THROUGH THE BULK OF THE FORECAST PERIOD...BUT MORE CLOSELY FOLLOWS THE TVCN AND GFS IN ACCELERATING OLAF NORTHEASTWARD AT THE END OF THE FORECAST PERIOD. LATEST UW-CIMSS AND SHIPS ANALYSES INDICATE SHEAR ON THE ORDER OF 5 KT OR LESS...WHILE WATER VAPOR IMAGERY SHOWS OLAF IN A COL BETWEEN HIGH-LEVEL RIDGES CENTERED TO THE DISTANT EAST AND WEST...WHICH IS SUPPLYING OUTFLOW CHANNELS TO THE NORTH AND SOUTH. SOME SMALL FLUCTUATIONS IN INTENSITY ARE EXPECTED INTO TONIGHT AS OLAF WILL REMAIN IN A LIGHT SHEAR ENVIRONMENT WITH SSTS OVER 29C. DIFFICULT TO ANTICIPATE EYEWALL REPLACEMENT CYCLES MAY COMPLICATE THE SHORT-TERM FORECAST INTENSITY FORECAST...BUT THE LONGER TERM OUTLOOK CALLS FOR A GRADUAL WEAKENING TREND TO BEGIN WEDNESDAY AND CONTINUE INTO FRIDAY. MORE RAPID WEAKENING IS FORECAST ON DAYS 4 AND 5 DUE TO LOWERING SSTS AND INCREASING SOUTHWESTERLY SHEAR ALONG THE FORECAST TRACK. THE OFFICIAL INTENSITY FORECAST REMAINS ABOVE THE INTENSITY CONSENSUS IVCN BUT BELOW SHIPS GUIDANCE IN THE SHORT TERM...AND IS MORE AGGRESSIVE THAN IVCN IN WEAKENING OLAF AT THE END OF THE FORECAST PERIOD...SIMILAR TO THE SHIPS GUIDANCE...BUT NOT AS AGGRESSIVE AS LGEM. FORECAST POSITIONS AND MAX WINDS INIT 20/1500Z 10.6N 141.3W 130 KT 150 MPH 12H 21/0000Z 11.3N 142.6W 135 KT 155 MPH 24H 21/1200Z 12.2N 144.0W 130 KT 150 MPH 36H 22/0000Z 13.2N 145.2W 125 KT 145 MPH 48H 22/1200Z 14.4N 146.1W 120 KT 140 MPH 72H 23/1200Z 17.1N 147.1W 110 KT 125 MPH 96H 24/1200Z 20.0N 147.0W 85 KT 100 MPH 120H 25/1200Z 22.5N 145.5W 65 KT 75 MPH $$ FORECASTER BIRCHARD