073
WTPA45 PHFO 210917 CCA
TCDCP5
HURRICANE OLAF DISCUSSION NUMBER 26...CORRECTED
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP192015
1100 PM HST TUE OCT 20 2015
ALTHOUGH OLAF CONTINUES TO PRESENT A FAIRLY IMPRESSIVE SATELLITE
SIGNATURE THIS EVENING...THE OVERALL PRESENTATION HAS DEGRADED OVER
THE PAST 6 HOURS. THE EYE HAS BECOME INCREASINGLY CLOUD-FILLED WHILE
SURROUNDING CONVECTION IS NOT AS INTENSE AS IT ONCE WAS. THE OUTFLOW
PATTERN ALOFT IS STILL FAIRLY SYMMETRIC...EXCEPT FOR SOME LIMITED
OUTFLOW IN THE NORTHWEST QUADRANT. THE OBSERVED SATELLITE TRENDS LED
TO LOWERING DVORAK DATA-T VALUES...WHILE CURRENT INTENSITY ESTIMATES
RANGED FROM 5.5/102 KT FROM PGTW...TO 6.0/115 KT FROM PHFO AND
SAB...WITH UW-CIMSS SATCON INDICATING AN INTENSITY NEAR 110 KT. A
CONSERVATIVE BLEND OF THESE ESTIMATES LEADS TO AN INITIAL INTENSITY
OF 115 KT FOR THIS ADVISORY.
THE INITIAL MOTION FOR THIS ADVISORY IS 300/08 KT...WITH OLAF
FINALLY MAKING THE EXPECTED TURN TOWARD THE WEST-NORTHWEST BEFORE
EVENTUALLY MOVING ON AN INCREASINGLY NORTHWARD VECTOR. A MID-LEVEL
RIDGE THAT HAD BEEN NORTH OF OLAF OVER THE PAST COUPLE OF DAYS IS
IN THE PROCESS OF WEAKENING AND SHIFTING SOUTHEASTWARD...WHICH IS
ALLOWING OLAF TO GAIN LATITUDE. ON WEDNESDAY AND THURSDAY THE
PATTERN WILL FEATURE A MID-LEVEL HIGH CENTERED EAST OF OLAF...
WITH A WEAKER MID-LEVEL RIDGE NORTH OF OLAF ASSOCIATED WITH A
HIGH CENTERED NEAR THE INTERNATIONAL DATE LINE. THIS IS EXPECTED TO
IMPART A STEERING MOTION TOWARD THE NORTHWEST AND THEN
NORTH-NORTHWEST...AS PASSING MID-LATITUDE SHORTWAVE TROUGHS TO
THE NORTH ENSURE THAT THE RIDGE NORTH OF OLAF REMAINS WEAK. A MORE
SIGNIFICANT BREAK IN THE RIDGE WILL BEGIN ON FRIDAY AND CONTINUE
INTO THE WEEKEND DUE TO A STRONGER SHORTWAVE TROUGH. OLAF IS
EXPECTED TO BECOME EMBEDDED IN THE MID-LATITUDE WESTERLIES BY THE
END OF THE FORECAST PERIOD...WHICH WILL STEER IT TOWARD THE
NORTHEAST.
THE TRACK GUIDANCE REMAINS TIGHTLY CLUSTERED OVER THE FIRST 3 TO 4
DAYS OF THE FORECAST...AND DIVERGES SOMEWHAT TOWARD THE END OF THE
FORECAST PERIOD AS OLAF BEGINS TO MOVE NORTHEASTWARD. THE UPDATED
FORECAST IS CLOSE TO THE PREVIOUS...AND THE RELIABLE MULTI-MODEL
CONSENSUS TVCN...BUT RIDES THE LEFT EDGE OF THE NARROW GUIDANCE
ENVELOPE THROUGH THE FIRST 72 HOURS. THE 96 AND 120 HOUR FORECAST
POSITIONS HAVE BEEN SHIFTED TO THE RIGHT OF THE PREVIOUS...TO BE IN
LINE WITH THE GFEX AND TVCN CONSENSUS...WHICH INDICATE A FASTER TURN
TOWARD THE NORTHEAST THAN PREVIOUSLY OFFICIALLY FORECAST.
LIGHT SHEAR AND SSTS BETWEEN 28C AND 29C OVER THE NEXT 24 TO 36
HOURS ARE EXPECTED TO LEAD TO LITTLE CHANGE IN OLAF/S INTENSITY.
INCREASING SHEAR AND GRADUALLY LOWERING SSTS WILL LEAD TO A GRADUAL
WEAKENING TREND FROM 48 TO 72 HOURS...WITH INCREASING SOUTHWESTERLY
SHEAR AND MORE RAPIDLY DIMINISHING SSTS THEREAFTER LEADING TO A MORE
RAPID WEAKENING. THE UPDATED FORECAST FOLLOWS TRENDS PRESENTED BY
THE PREVIOUS...AS WELL AS THE SHIPS...LGEM AND IVCN INTENSITY
CONSENSUS...AFTER ACCOUNTING FOR A LOWER THAN EXPECTED INITIAL
INTENSITY.
FORECAST POSITIONS AND MAX WINDS
INIT 21/0900Z 11.5N 143.8W 115 KT 135 MPH
12H 21/1800Z 12.3N 144.7W 115 KT 135 MPH
24H 22/0600Z 13.5N 145.8W 110 KT 125 MPH
36H 22/1800Z 14.7N 146.5W 110 KT 125 MPH
48H 23/0600Z 16.0N 146.9W 100 KT 115 MPH
72H 24/0600Z 19.1N 147.0W 85 KT 100 MPH
96H 25/0600Z 21.5N 145.5W 70 KT 80 MPH
120H 26/0600Z 24.0N 143.5W 55 KT 65 MPH
$$
FORECASTER BIRCHARD
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