068 
 WTPA45 PHFO 242058
 TCDCP5
 
 HURRICANE OLAF DISCUSSION NUMBER  40
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP192015
 1100 AM HST SAT OCT 24 2015
  
 OLAF IS WEAKENING IN THE FACE OF SOUTHWESTERLY VERTICAL WIND
 SHEAR...ESTIMATED TO BE NEAR 30 KT...AND THE EYE IS NO LONGER
 VISIBLE IN CONVENTIONAL SATELLITE IMAGERY. A 1615Z WINDSAT PASS
 HOWEVER INDICATED AN EYE-LIKE FEATURE WITH BREAKS IN THE EYE WALL IN
 THE SOUTHEAST SEMICIRCLE. SUBJECTIVE DVORAK CURRENT INTENSITY
 ESTIMATES WERE 5.0/90 KT FROM PHFO/SAB/PGTW...WHILE SATCON FROM
 UW-CIMSS IS ALSO TRENDING DOWN...WITH THE LATEST AVAILABLE INTENSITY
 ESTIMATE NEAR 95 KT. THE INITIAL INTENSITY USED FOR THIS ADVISORY IS
 A SOMEWHAT CONSERVATIVE 95 KT.
  
 LATEST ANALYSES FEATURE A NORTHEAST TO SOUTHWEST ORIENTED
 DEEP-LAYER RIDGE TO THE EAST OF OLAF...AND AN EAST TO WEST ORIENTED
 RIDGE CENTERED NEAR THE DATE LINE. OLAF IS MOVING NORTH-
 NORTHEAST...030/07 KT...INTO A SIGNIFICANT BREAK IN THE RIDGE...AND
 INCREASINGLY INTO THE MID-LATITUDE WESTERLIES. NORTH OF THE DATE
 LINE RIDGE...A FAST-MOVING SHORTWAVE TROUGH IN THE WESTERLIES ALOFT
 IS SEEN MOVING EAST-SOUTHEAST NEAR 55 MPH. THIS FEATURE IS
 RESPONSIBLE FOR INTRODUCING INCREASED UNCERTAINTY TO THE TRACK
 FORECAST FOR OLAF...ESPECIALLY IN LATER FORECAST PERIODS. WHEREAS
 RECENT MODEL ITERATIONS TRENDED TOWARD A WEAKER TROUGH...THE LATEST
 GUIDANCE IS NOW INDICATING A DEEPER TROUGH TAKING OLAF FURTHER EAST
 AT A FASTER RATE OF SPEED BEFORE THE TROUGH LIFTS. THE DATE LINE
 RIDGE IS STILL EXPECTED TO SHIFT RAPIDLY EAST AND BUILD NORTH OF
 OLAF AS THE TROUGH LIFTS OUT...INDUCING A TURN TOWARD THE
 WEST...WITH SIGNIFICANT UNCERTAINTY SURROUNDING THE TIMING AND
 LOCATION OF THIS TURN. DUE TO THE LACK OF MODEL CONSISTENCY...THE
 OFFICIAL FORECAST REPRESENTS A BLEND OF THE PREVIOUS TRACK FORECAST
 AND THE LATEST TVCN AND FSSE CONSENSUS GUIDANCE...TAKING OLAF NORTH-
 NORTHEASTWARD THROUGH DAY 3 BEFORE TURNING IT SHARPLY BACK TOWARD 
 THE WEST. 
  
 STRONG SOUTHWESTERLY SHEAR IS FORECAST TO DIMINISH SOMEWHAT IN THE
 SHORT TERM AS A SHORTWAVE TROUGH NORTH OF OLAF LIFTS OUT...AND
 BEFORE A SECOND SHORTWAVE /DISCUSSED ABOVE/ ARRIVES IN ABOUT 36
 HOURS. THE FORECAST TRACK TAKES OLAF OVER STEADILY DECREASING SSTS
 THROUGH DAY 3...AFTER WHICH TIME IT IS EXPECTED TO BE OVER SSTS
 BETWEEN 25C AND 26C. THE UPDATED INTENSITY FORECAST CLOSELY FOLLOWS
 GUIDANCE PROVIDED BY THE INTENSITY CONSENSUS IVCN...AND INDICATES
 THAT RAPID WEAKENING IN THE FIRST 24 HOURS OF THE FORECAST WILL BE
 FOLLOWED BY A SLOWER RATE OF WEAKENING. SHIPS RESPONDS TO THE
 DECREASING SSTS AND PERSISTENT SHEAR BY DISSIPATING OLAF AFTER 72
 HOURS. THE OFFICIAL FORECAST MAINTAINS OLAF AS A TROPICAL
 DEPRESSION AS IT MOVES WEST ON DAYS 4 AND 5...BUT THERE IS
 CONSIDERABLE UNCERTAINTY AS TO WHETHER OLAF WILL BE ABLE TO SURVIVE
 THE MODERATE TO STRONG SOUTHWESTERLY SHEAR IT ENCOUNTERS BEFORE
 THAT TIME. 
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  24/2100Z 19.8N 145.0W   95 KT 110 MPH
  12H  25/0600Z 20.8N 144.5W   80 KT  90 MPH
  24H  25/1800Z 21.9N 143.9W   70 KT  80 MPH
  36H  26/0600Z 23.2N 142.8W   60 KT  70 MPH
  48H  26/1800Z 24.5N 141.1W   50 KT  60 MPH
  72H  27/1800Z 26.1N 138.5W   35 KT  40 MPH
  96H  28/1800Z 26.5N 140.0W   30 KT  35 MPH
 120H  29/1800Z 26.5N 142.5W   30 KT  35 MPH
  
 $$
 
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