238 
 WTPA44 PHFO 051458
 TCDCP4
 
 HURRICANE JIMENA DISCUSSION NUMBER  40
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP132015
 500 AM HST SAT SEP 05 2015
  
 THE CLOUD-FILLED EYE OF HURRICANE JIMENA HAD BEEN APPARENT IN 
 INFRARED IMAGERY THROUGH MOST OF THE NIGHT...WITH COLD CONVECTIVE
 CLOUD TOPS PRIMARILY LOCATED IN THE EASTERN SEMICIRCLE. HOWEVER...IN
 THE LAST COUPLE OF SATELLITE IMAGES THE APPEARANCE HAS DEGRADED
 SOMEWHAT RAPIDLY...AND THE EYE IS NO LONGER EVIDENT. THIS IS
 APPARENTLY DUE TO DRY AIR WORKING ITS WAY INTO THE CORE OF THE 
 CYCLONE FROM THE WEST...AIDED BY SOUTHWESTERLY SHEAR THAT IS 
 OBJECTIVELY ANALYZED BY THE UNIVERSITY OF WISCONSIN COOPERATIVE 
 INSTITUTE FOR METEOROLOGICAL SATELLITE STUDIES /UW-CIMSS/ AS BEING 
 NEAR 20 KT. DVORAK DATA-T VALUES THIS TIME AROUND WERE T3.5/55 KT 
 FROM SAB...T4.0/65 KT FROM PHFO AND T4.5/77 KT FROM PGTW. A BLEND
 OF THESE ESTIMATES...WITH A NOD TOWARD THE LATEST IMAGERY...
 SUPPORTS LOWERING THE INITIAL INTENSITY TO 70 KT FOR THIS ADVISORY. 
 
 THE INITIAL MOTION ESTIMATE FOR THIS ADVISORY IS 320/06 KT...WITH 
 JIMENA EMBEDDED WITHIN A SOMEWHAT COMPLEX STEERING FLOW. THE
 LOW-LEVEL CENTER IS ESTIMATED TO BE SOUTHWEST OF THE REMAINING DEEP
 CONVECTION...AS 0946Z GPM AND 1058Z GCOM OVERPASSES INDICATED A
 NORTHEASTWARD TILT WITH HEIGHT. THE UPDATED FORECAST TRACK AND
 REASONING IS NOT THAT MUCH DIFFERENT THAN THE PREVIOUS...BUT IS ONCE
 AGAIN A LITTLE FASTER AND TO THE RIGHT THROUGH MOST OF THE FORECAST
 PERIOD. 
 
 DEEP LAYER HIGHS ARE CENTERED NEARBY TO THE SOUTHEAST...AND TO THE
 DISTANT NORTH OF JIMENA. OVER THE WEEKEND...THE RIDGE TO THE
 SOUTHEAST WILL BUILD TO THE SOUTH OF JIMENA...WHILE THE RIDGE TO THE
 NORTH MOVES LITTLE. THIS IS EXPECTED TO KEEP THE SYSTEM MOVING ALONG
 ON A MOTION VECTOR CLOSE TO WHAT IS CURRENTLY OBSERVED...AND TOWARD
 A WEAKNESS IN THE RIDGE TO ITS NORTHWEST. EARLY NEXT WEEK...JIMENA
 WILL BEGIN TO FEEL THE INFLUENCE OF THE RIDGE TO THE NORTH AS IT
 BUILDS TO THE NORTHWEST OF THE CYCLONE. THE WEAKNESS IN THE RIDGE
 WILL SHIFT TO THE SOUTHWEST OF THE SYSTEM...AND JIMENA WILL MOVE
 GENERALLY WESTWARD FROM MONDAY THROUGH WEDNESDAY...WITH THE MOTION
 VECTOR ACTUALLY JUST SOUTH OF DUE WEST ON DAYS 4 AND 5. THE 0600Z
 RUN OF THE GFS SHIFTED NORTHWARD TOWARD THE PREVIOUS FORECAST TRACK
 AND THE 0000Z ECMWF GUIDANCE...AND THE 4 AND 5 DAY FORECAST POSITIONS
 ARE NOW NEARLY ON TOP OF THE GFEX CONSENSUS. THE OFFICIAL FORECAST 
 TRACK IS NEAR THE CENTER OF A WIDENING DYNAMICAL GUIDANCE ENVELOPE 
 THROUGH THE FIRST COUPLE OF DAYS. THEREAFTER...IT IS ON THE SOUTHERN 
 SIDE OF THE GUIDANCE ENVELOPE...AND SOMEWHAT SLOWER AND TO THE SOUTH 
 OF THE TVCN WHICH IS BEING PULLED NORTHWARD DUE TO THE GFDI...WHICH 
 IS ONE OF THE NORTHERNMOST MEMBERS. 
 
 ALTHOUGH IT APPEARED THAT JIMENA BRIEFLY INTENSIFIED EARLY IN THE
 NIGHT...RECENT OBSERVATIONS INDICATE THE OTHERWISE EXPECTED WEAKENING
 TREND MAY BE OCCURRING FASTER THAN EXPECTED. EITHER WAY...JIMENA IS
 NOT LIKELY TO REMAIN A HURRICANE FOR MUCH LONGER...AND THE UPDATED
 INTENSITY FORECAST ANTICIPATES WEAKENING TO A TROPICAL STORM BY
 TONIGHT. ALTHOUGH THE FORECAST TRACK TAKES JIMENA OVER WATER
 TEMPERATURES WARM ENOUGH TO SUPPORT A HURRICANE...THE DEBILITATING
 EFFECTS OF PERSISTENT WESTERLY SHEAR ARE EXPECTED TO LEAD TO JIMENA
 BECOMING A TROPICAL DEPRESSION AS IT PASSES NORTH OF THE MAIN 
 HAWAIIAN ISLANDS LATE IN THE FORECAST PERIOD. THE INTENSITY FORECAST 
 IS VERY SIMILAR TO THE PREVIOUS AND IS A LITTLE STRONGER THAN 
 SHIPS...WHICH INDICATES DISSIPATION BY DAY 5.
 
 A SATELLITE ALTIMETER OVERPASS NEAR 0422Z WAS UTILIZED TO FINE TUNE 
 THE 12 FOOT SEAS RADII IN THE WESTERN SEMICIRCLE...WHILE AN ASCAT 
 PASS AROUND 0700Z WAS USED TO HELP DEFINE WIND RADII IN THE EASTERN 
 SEMICIRCLE. 
 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  05/1500Z 21.3N 146.4W   70 KT  80 MPH
  12H  06/0000Z 22.2N 146.9W   65 KT  75 MPH
  24H  06/1200Z 23.4N 147.7W   60 KT  70 MPH
  36H  07/0000Z 24.4N 148.7W   55 KT  65 MPH
  48H  07/1200Z 25.0N 149.8W   50 KT  60 MPH
  72H  08/1200Z 25.3N 152.2W   40 KT  45 MPH
  96H  09/1200Z 25.0N 155.5W   35 KT  40 MPH
 120H  10/1200Z 24.5N 159.0W   30 KT  35 MPH
  
 $$
 
 FORECASTER BIRCHARD