803 
 WTPA41 PHFO 091457
 TCDCP1
 
 TROPICAL STORM ELA DISCUSSION NUMBER   7
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP042015
 500 AM HST THU JUL 09 2015
  
 A 1052Z VIIRS DAY/NIGHT BAND IMAGE WAS INSTRUMENTAL IN HELPING TO
 LOCATE THE PARTIALLY EXPOSED CENTER OF ELA THIS MORNING. LATEST
 DVORAK SUBJECTIVE INTENSITY ESTIMATES FROM HFO/SAB/JTWC INDICATE
 THAT ELA IS A WEAK SYSTEM...WITH CURRENT INTENSITY VALUES RANGING
 FROM 1.0 TO 1.5. MEANWHILE...INFRARED SATELLITE IMAGES SHOW PULSING
 DEEP CONVECTION JUST NORTHEAST OF THE CENTER OVER THE PAST SEVERAL
 HOURS...SIMILAR TO WHAT WAS SEEN WHEN U.S. AIR FORCE HURRICANE
 HUNTERS FOUND TROPICAL STORM FORCE WINDS EARLIER IN THE EVENING.
 THEREFORE...ELA IS BEING MAINTAINED AS A 35 KT TROPICAL STORM WITH
 THIS ADVISORY. 
  
 THE INITIAL MOTION ESTIMATE IS 315/11 KT...WITH ELA BEING STEERED
 TOWARD THE NORTHWEST BY A DEEP LAYER RIDGE TO THE EAST. THE CYCLONE
 IS AN AREA OF MODERATE SOUTHWESTERLY SHEAR...ANALYZED AS BEING AS
 HIGH AS 25 KT BY UW-CIMSS. EVEN GREATER SHEAR VALUES LIE ALONG THE
 FORECAST TRACK...ESPECIALLY AFTER THE FIRST 24 HOURS...MAINLY DUE TO
 THE PRESENCE OF A SLOW-MOVING CLOSED LOW ALOFT CENTERED TO THE
 NORTHEAST OF THE MAIN HAWAIIAN ISLANDS. 
 
 THE INCREASING SHEAR IS FORECAST TO LEAD TO THE EVENTUAL DEMISE OF
 THE SYSTEM...WITH SHIPS GUIDANCE INDICATING DISSIPATION BY DAY 2.
 THE OFFICIAL FORECAST FOLLOWS THIS TREND...BUT IS NOT AS AGGRESSIVE
 IN WEAKENING THE SYSTEM IN DEFERENCE TO THE GFS AND ECMWF...WHICH
 MAINTAIN A CLOSED LOW THROUGH DAY 3 BEFORE THE SYSTEM BECOMES A
 WESTWARD-MOVING OPEN WAVE ON DAY 4. THEREFORE...THE EXPECTATION IS
 THAT ELA WILL BECOME AN INCREASINGLY SHALLOW SYSTEM TONIGHT AND
 FRIDAY...WHICH WILL ALLOW THE LOW-LEVEL TRADE WIND FLOW TO BEGIN 
 CARRYING IT WESTWARD. ELA IS THEN FORECAST TO WEAKEN TO A REMNANT 
 LOW JUST NORTH OF THE MAIN HAWAIIAN ISLANDS THIS WEEKEND BEFORE 
 DISSIPATING. THE UPDATED TRACK FORECAST WAS NUDGED TO THE RIGHT IN 
 THE EARLIER PERIODS OF THE FORECAST...TO THE LEFT AT THE END OF THE 
 FORECAST...AND THE FORWARD MOTION HAS BEEN DECREASED AFTER 36 
 HOURS...FOLLOWING TRENDS PRESENTED BY THE TVCX CONSENSUS.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  09/1500Z 20.2N 146.1W   35 KT  40 MPH
  12H  10/0000Z 21.4N 147.4W   35 KT  40 MPH
  24H  10/1200Z 22.5N 149.5W   30 KT  35 MPH
  36H  11/0000Z 23.4N 151.4W   25 KT  30 MPH
  48H  11/1200Z 23.8N 153.6W   25 KT  30 MPH
  72H  12/1200Z 24.0N 158.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
  96H  13/1200Z...DISSIPATED
  
 $$
 
 FORECASTER BIRCHARD