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 761 
 WTPA44 PHFO 060900
 TCDCP4
 
 TROPICAL STORM JIMENA DISCUSSION NUMBER  43
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP132015
 1100 PM HST SAT SEP 05 2015
  
 JIMENA CONTINUES TO BE EMBEDDED WITHIN A RATHER HARSH ENVIRONMENT...
 CHARACTERIZED BY SIGNIFICANT /NEAR 25 KT PER UW-CIMSS ANALYSIS/ 
 SOUTHWESTERLY VERTICAL WIND SHEAR THAT IS HELPING TO ENTRAIN DRY  
 MID- AND UPPER-LEVEL AIR INTO THE CIRCULATION. SATELLITE IMAGERY 
 SHOWS SEVERELY RESTRICTED OUTFLOW IN THE SOUTHWEST SEMICIRCLE...WITH
 A CURVED BAND OF DEEP CONVECTION WRAPPING IN TOWARD THE CENTER FROM
 THE NORTH. RECENT MICROWAVE OVERPASSES INCLUDE A RECENTLY ARRIVED
 0526Z SSMIS IMAGE AS WELL AS A 0326Z SSMIS IMAGE...BOTH OF WHICH
 SHOW THAT THE LOW LEVEL CIRCULATION CENTER /LLCC/ IS BECOMING
 DETACHED FROM THE UPPER LEVEL CIRCULATION...WITH THE SYSTEM TILTED
 TOWARD THE NORTH-NORTHEAST WITH HEIGHT. LATEST DVORAK CURRENT
 INTENSITY /CI/ ESTIMATES WERE 3.5/55 KT FROM PHFO AND PGTW...WHILE
 SAB INDICATED 3.0/45 KT. ADT CI VALUES FROM UW-CIMSS HAVE BEEN RIGHT
 AROUND 3.2/49 KT FOR THE PAST COUPLE OF HOURS. A BLEND OF THE
 INTENSITY ESTIMATES LEADS TO AN INITIAL INTENSITY OF 50 KT FOR THIS
 ADVISORY...THUS INDICATING THAT JIMENA HAS RAPIDLY WEAKENED OVER THE
 PAST 24 HOURS. 
 
 THE LLCC IS ESTIMATED TO BE ON THE SOUTHWEST SIDE OF THE DIMINISHING
 COLD CLOUD CANOPY...AND THE INITIAL MOTION FOR THIS PACKAGE IS
 325/07 KT. THERE IS A GREATER THAN NORMAL AMOUNT OF UNCERTAINTY IN
 THE INITIAL MOTION ESTIMATE...AS THE LLCC IS SOMEWHAT DIFFICULT TO
 PINPOINT...AND THE AFOREMENTIONED 0526Z SSMIS IMAGE SUGGESTS THAT
 THE INITIAL POSITION FOR THIS PACKAGE MAY HAVE BEEN A LITTLE TOO
 FAR TO THE SOUTHWEST. JIMENA CONTINUES TO MOVE BETWEEN A MID-LEVEL
 RIDGE THAT EXTENDS FROM NORTH THROUGH EAST THROUGH SOUTHEAST OF THE
 SYSTEM...TOWARD A TROUGH TO THE NORTHWEST. AFTER ABOUT 36 HOURS... 
 THE RIDGE TO THE NORTH IS FORECAST TO BRIEFLY STRENGTHEN BEFORE THEN 
 BUILDING TO THE WEST AND NORTHWEST OF JIMENA. THIS WILL RESULT IN A 
 TURN TOWARD THE WEST...WITH THE AMOUNT OF TURN VARYING AMONG THE 
 DIFFERENT MODELS...PRIMARILY DUE TO DIFFERENCES IN THE STRENGTH AND 
 POSITION OF THE BUILDING RIDGE. THE UPDATED TRACK FORECAST FOLLOWS 
 THE TRAJECTORY OF THE PREVIOUS VERY CLOSELY...BUT IS FASTER AND TO 
 THE RIGHT THROUGH 48 HOURS...AND THEN VERY CLOSE...BUT JUST NORTH 
 OF THE PREVIOUS THROUGH DAY 5. WHILE THE OFFICIAL TRACK FORECAST
 HAD BEEN ON THE SOUTH SIDE OF A GUIDANCE ENVELOPE THAT SHOWS
 INCREASING SPREAD IN THE LATER PERIODS...IT NOW LIES BETWEEN THE
 TVCN AND GFEX CONSENSUS...AS THE LATEST ECMWF BUILDS A STRONGER
 RIDGE TO THE WEST OF JIMENA...THEREBY IMPARTING A SOUTHWESTERLY
 MOTION TO THE CYCLONE ON DAYS 3 THROUGH 5. 
 
 PERSISTENT AND RELATIVELY STRONG SHEAR...FIRST FROM THE SOUTHWEST...
 AND THEN FROM THE WEST AND NORTHWEST...IS EXPECTED TO LEAD TO THE
 EVENTUAL DEMISE OF JIMENA. A BRIEF RELAXATION OF THE SHEAR IS
 POSSIBLE ON SUNDAY...AND THUS THE WEAKENING TREND IS FORECAST TO
 ABATE BRIEFLY...UNTIL SHEAR INCREASES AGAIN THEREAFTER. GIVEN THAT
 THE RECENT RATE OF WEAKENING HAS BEEN WELL ANTICIPATED BY SHIPS
 GUIDANCE...AND LESS SO BY OTHER MEMBERS OF THE INTENSITY CONSENSUS
 IVCN...THE UPDATED INTENSITY FORECAST HAS GIVEN ADDITIONAL WEIGHT TO
 SHIPS. THIS IS ESPECIALLY TRUE IN THE LATER PERIODS WHERE IVCN
 INDICATES RE-STRENGTHENING DUE TO CONTRIBUTIONS FROM THE GFDL...WHICH
 BRINGS JIMENA BACK NEAR HURRICANE STRENGTH ON DAY 5. THE OFFICIAL
 INTENSITY FORECAST REMAINS A LITTLE CONSERVATIVE IN THAT IT 
 MAINTAINS A VIABLE TROPICAL CYCLONE THROUGH DAY 4...WHEREAS SHIPS 
 DISSIPATES JIMENA AFTER 60 HOURS. 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  06/0900Z 22.9N 147.9W   50 KT  60 MPH
  12H  06/1800Z 23.9N 148.7W   45 KT  50 MPH
  24H  07/0600Z 24.8N 149.9W   45 KT  50 MPH
  36H  07/1800Z 25.4N 151.1W   40 KT  45 MPH
  48H  08/0600Z 25.6N 152.3W   35 KT  40 MPH
  72H  09/0600Z 25.2N 155.5W   30 KT  35 MPH
  96H  10/0600Z 25.0N 159.0W   30 KT  35 MPH
 120H  11/0600Z 25.0N 162.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
  
 $$
 
 FORECASTER BIRCHARD
 
 
 
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