368 
 WTPA45 PHFO 190901
 TCDCP5
 
 TROPICAL DEPRESSION FIVE-C DISCUSSION NUMBER   2
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP052015
 1100 PM HST FRI SEP 18 2015
  
 LATEST SATELLITE IMAGES INDCIATE THAT THE DEPRESSION HAS NOT 
 ORGANIZED SIGNIFICANTLY SINCE THE PREVIOUS ADVISORY. DEEP
 CONVECTION IS PULSING CLOSE TO THE DIFFICULT TO PINPOINT LOW LEVEL
 CIRCULATION CENTER /LLCC/...WITH SUBJECTIVE DVORAK INTENSITY
 ESTIMATES FROM PHFO/PGTW/KNES NEARLY ONE DEGREE APART IN THEIR 
 CENTER POSITIONS. DESPITE THESE DIFFERENCES...THESE AGENCIES ALL 
 DERIVED 2.0/30 KT...AND THAT WILL BE THE INITIAL INTENSITY USED FOR 
 THIS ADVISORY. 
 
 A 0359Z SSMIS OVERPASS HELPED IN CENTER LOCATION...WITH THE CENTER 
 ESTIMATED TO BE ON THE SOUTHWEST SIDE OF THE COLD CLOUD TOPS...DUE 
 TO THE FACT THAT THE CYCLONE IS EMBEDDED IN AN ENVIRONMENT 
 CHARACTERIZED BY MODERATE SOUTHWESTERLY SHEAR. THE INITIAL MOTION 
 ESTIMATE FOR THIS ADVISORY IS A SOMEWHAT UNCERTAIN 030/08 KT...DUE 
 TO THE LACK OF CONFIDENCE IN THE INITIAL POSITION OF THE LLCC. THE 
 MOTION OF THE CYCLONE WILL LARGELY BE CONTROLLED BY THE FLOW BETWEEN 
 AN APPROACHING CLOSED LOW ALOFT TO THE NORTHWEST AND A NORTH-SOUTH 
 ORIENTED RIDGE FORECAST TO DEVELOP NEAR THE MAIN HAWAIIAN ISLANDS. 
 WHILE INITIALLY MOVING ON A MOTION VECTOR EAST OF NORTH...THE SYSTEM 
 WILL TURN TOWARD THE NORTH AND ACCELERATE SLIGHTLY ON SUNDAY AND 
 MONDAY BEFORE TURNING TOWARD THE NORTH-NORTHWEST AND BECOMING 
 EXTRATROPICAL AT THE LATER FORECAST PERIODS. THE UPDATED TRACK 
 FORECAST IS VERY CLOSE TO THE PREVIOUS...AND LIES CLOSE TO THE 
 TIGHTLY CLUSTERED RELIABLE TRACK GUIDANCE. IT IS WORTH NOTING 
 HOWEVER THAT THERE ARE SIGNIFICANT ALONG TRACK DIFFERENCES BETWEEN 
 MODELS DUE TO DIFFERENCES IN THE FORECAST FORWARD SPEED OF THE 
 CYCLONE. 
  
 SLOW INTENSIFICATION IS STILL EXPECTED IN THE SHORT TERM. THE
 CYCLONE WILL BE MOVING OVER VERY WARM SEA SURFACE TEMPERATURES
 OVER THE NEXT TWO DAYS...WITH WATER TEMPERATURES STEADILY
 DIMINISHING THEREAFTER. THE MORE SIGNIFICANT CHALLENGE WITH RESPECT
 TO THE INTENSITY FORECAST IS HOW THE SYSTEM RESPONDS TO PERSISTENT 
 SOUTHWESTERLY WIND SHEAR...FORECAST TO INCREASE FROM 15-20 KT TO 30-
 40 KT IN THE LATER FORECAST PERIODS. THE SHEAR CONTINUES TO RESTRICT 
 OUTFLOW IN THE SOUTHWEST QUADRANT BUT IS PRODUCING AN OUTFLOW 
 CHANNEL TO THE NORTH AND EAST. AS THE DISTANCE BETWEEN THE CLOSED 
 LOW ALOFT AND THE CYCLONE DECREASES...VERTICAL WIND SHEAR WILL RAMP 
 UP QUICKLY...AND LIMIT THE INTENSIFICATION TREND. THE UPDATED 
 FORECAST IS CLOSE TO THE PREVIOUS AND CLOSELY FOLLOWS SHIPS 
 GUIDANCE. THE FORECAST ASSUMES THAT THE CYCLONE WILL REMAIN INTACT 
 IN THE LATER PERIODS...AND WILL BECOME EXTRATROPICAL AS IT 
 INCREASINGLY INTERACTS WITH THE FLOW AROUND THE CLOSED LOW ALOFT TO 
 THE NORTHWEST AND WEST. 
 
 A TROPICAL STORM WATCH REMAINS IN PLACE FOR THE CENTRAL PORTIONS OF
 THE PAPAHANAUMOKUAKEA NATIONAL MARINE MONUMENT...FROM LISIANSKI
 ISLAND TO MARO REEF TO FRENCH FRIGATE SHOALS. IF CURRENT TRENDS
 CONTINUE...WARNINGS WILL LIKELY BE REQUIRED ON SATURDAY. 
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  19/0900Z 18.5N 173.7W   30 KT  35 MPH
  12H  19/1800Z 19.7N 173.3W   35 KT  40 MPH
  24H  20/0600Z 21.3N 172.7W   40 KT  45 MPH
  36H  20/1800Z 23.2N 172.3W   45 KT  50 MPH
  48H  21/0600Z 25.3N 172.2W   50 KT  60 MPH
  72H  22/0600Z 30.4N 172.3W   45 KT  50 MPH
  96H  23/0600Z 36.0N 173.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 120H  24/0600Z 42.0N 177.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
  
 $$
 
 FORECASTER BIRCHARD