284 
 WTPA45 PHFO 191500
 TCDCP5
 
 TROPICAL DEPRESSION FIVE-C DISCUSSION NUMBER   3
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP052015
 500 AM HST SAT SEP 19 2015
  
 INFRARED SATELLITE IMAGES SHOW THAT A MASS OF COLD CLOUD TOPS
 ASSOCIATED WITH THE CYCLONE HAS PERSISTED SINCE THE PREVIOUS
 ADVISORY. IN THE ABSENCE OF ANY TIMELY OR USEFUL MICROWAVE PASSES...
 BI-SPECTRAL IMAGERY SHOWS HINTS OF LOW CLOUD LINES CURVING INTO WHAT
 APPEARS TO BE A LOW LEVEL CIRCULATION CENTER LOCATED ON THE
 NORTHWESTERN EDGE OF THE COLD CLOUD TOPS. THE DIFFICULTY IN FINDING
 THE LOW LEVEL CENTER IS HIGHLIGHTED BY THE LATEST SUBJECTIVE DVORAK
 INTENSITY ESTIMATES FROM PHFO/PGTW/KNES...WHICH ARE NEARLY 2 DEGREES
 APART IN THEIR CENTER POSITION ESTIMATES. LATEST T-NUMBERS RANGE FROM
 2.0/30 KT FROM PHFO/KNES WHILE JTWC DERIVED 2.5/35 KT. DUE TO
 UNCERTAINTIES ASSOCIATED WITH THE POSITION OF THE LOW LEVEL
 CENTER...THE INITIAL INTENSITY FOR THIS ADVISORY WILL BE MAINTAINED
 AT 30 KT. 
 
 FOR REASONS DESCRIBED ABOVE...THE INITIAL MOTION VECTOR FOR THIS
 ADVISORY IS A SOMEWHAT UNCERTAIN 045/08 KT. THE DEPRESSION IS
 CURRENTLY BEING STEERED BY THE FLOW BETWEEN A MID- AND UPPER-LEVEL 
 RIDGE LOCATED TO ITS SOUTHEAST...AND AN APPROACHING CLOSED LOW ALOFT 
 CENTERED TO THE DISTANT NORTHWEST. THIS SHOULD CONTINUE THROUGH THE 
 NEXT 12 HOURS OR SO...WITH A TURN TOWARD THE NORTH AND AN INCREASE 
 IN FORWARD SPEED EXPECTED THEREAFTER. THIS WILL OCCUR AS THE DEEP 
 LAYER FLOW BECOMES INCREASINGLY SOUTHERLY...AS THE LOW TO THE 
 NORTHWEST DRAWS CLOSER...AND A NORTH-SOUTH ORIENTED RIDGE DEVELOPS 
 NEAR THE MAIN HAWAIIAN ISLANDS. THE UPDATED TRACK FORECAST IS ONCE 
 AGAIN CLOSE TO THE PREVIOUS...AND LIES NEAR THE MIDDLE OF THE 
 RELIABLE GUIDANCE...WHICH IS TIGHTLY CLUSTERED IN TAKING THE CENTER 
 OF THE CYCLONE VERY CLOSE TO LAYSAN. ALTHOUGH THERE ARE LITTLE IN 
 THE WAY OF ACROSS-TRACK DIFFERENCES BETWEEN THE RELIABLE TRACK 
 MODELS...THERE REMAIN SIGNIFICANT ALONG TRACK DIFFERENCES BETWEEN 
 MODELS DUE TO DIFFERENCES IN THE FORECAST FORWARD SPEED OF THE 
 CYCLONE.
  
 SOME INTENSIFICATION IS EXPECTED IN THE SHORT TERM AS THE CYCLONE
 MOVES OVER VERY WARM SEA SURFACE TEMPERATURES...WITH WATER
 TEMPERATURES STEADILY DIMINISHING AFTER ABOUT 48 HOURS. THE MORE
 SIGNIFICANT CHALLENGE WITH RESPECT TO THE INTENSITY FORECAST
 HOWEVER CONTINUES TO HINGE ON THE INTERACTION BETWEEN THE CYCLONE
 AND THE PERSISTENT SOUTHWESTERLY TO SOUTHERLY WIND SHEAR TO WHICH
 IT WILL BE EXPOSED. AS THE DISTANCE BETWEEN THE CLOSED LOW ALOFT TO
 THE NORTHWEST AND THE CYCLONE DECREASES...VERTICAL WIND SHEAR WILL
 RAMP UP QUICKLY...INCREASING FROM CURRENT VALUES OF 15-20 KT TO
 30-40 KT AFTER 72 HOURS. THE UPDATED INTENSITY FORECAST ANTICIPATES
 SHORT TERM STRENGTHENING TO A TROPICAL STORM IN LINE WITH LATEST 
 SHIPS GUIDANCE. GRADUAL WEAKENING...AND TRANSITION TO AN 
 EXTRATROPICAL LOW...IS EXPECTED BEFORE DISSIPATION OCCURS ON DAY 5. 
 THIS WILL OCCUR AS THE SYSTEM GETS ENGULFED IN THE LARGE CYCLONIC 
 CIRCULATION ASSOCIATED WITH THE APPROACHING CLOSED LOW ALOFT. 
 
 THE LATEST FORECAST NECESSITATES THE ISSUANCE OF A TROPICAL
 STORM WARNING FOR CENTRAL PORTIONS OF THE PAPAHANAUMOKUAKEA MARINE
 NATIONAL MONUMENT...FROM FRENCH FRIGATE SHOALS TO MARO REEF
 TO LISIANSKI ISLAND. GIVEN THE INHERENT UNCERTAINTIES IN TRACK AND
 INTENSITY FORECASTS...A TROPICAL STORM WATCH HAS BEEN ISSUED FOR
 THE AREA FROM LISIANSKI ISLAND TO PEARL AND HERMES.  
 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  19/1500Z 19.4N 173.3W   30 KT  35 MPH
  12H  20/0000Z 20.5N 173.0W   35 KT  40 MPH
  24H  20/1200Z 22.1N 172.5W   40 KT  45 MPH
  36H  21/0000Z 23.9N 172.1W   45 KT  50 MPH
  48H  21/1200Z 26.5N 171.8W   45 KT  50 MPH
  72H  22/1200Z 31.2N 172.5W   40 KT  45 MPH
  96H  23/1200Z 37.5N 174.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 120H  24/1200Z...DISSIPATED
  
 $$
 
 FORECASTER BIRCHARD