934 
 WTPZ43 KNHC 290854
 TCDEP3
 TROPICAL STORM JIMENA DISCUSSION NUMBER   2
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP132009
 200 AM PDT SAT AUG 29 2009
  
 ENHANCED INFRARED SATELLITE IMAGERY INDICATES THAT THE CENTER IS
 LIKELY EMBEDDED IN A SMALL MASS OF DEEP CONVECTION TO -80C...WITH A
 WELL-DEFINED CURVED BAND ARCING OUTWARD IN THE NORTHERN SEMICIRCLE. 
 OVERALL...THE CLOUD PATTERN HAS EXHIBITED INCREASED ORGANIZATION
 DURING THE LAST SEVERAL HOURS. DVORAK T-NUMBERS OF T 2.5 AND T 3.0
 FROM SAB AND TAFB...RESPECTIVELY. THEREFORE...THE DEPRESSION IS
 BEING UPGRADED TO TROPICAL STORM JIMENA WITH A 35 KT INITIAL
 INTENSITY.
  
 JIMENA CONTINUES TO MOVE ON A GENERAL WESTERLY COURSE...WITH A
 SOMEWHAT UNCERTAIN INITIAL MOTION ESTIMATE OF 280/10. MODEL
 GUIDANCE SHOWS A MID-LEVEL RIDGE COVERING CENTRAL/WESTERN MEXICO
 WHICH SHOULD STEER JIMENA ON A WESTWARD TO WEST-NORTHWESTWARD
 COURSE DURING THE NEXT 36-48 HOURS WITH SOME DECREASE IN FORWARD
 SPEED. THEREAFTER...GLOBAL MODELS DEPICT AN AMPLIFYING LONGWAVE
 TROUGH OVER THE EAST PACIFIC ALONG 135 WEST WHICH SHOULD CAUSE THE
 MID-LEVEL RIDGE OVER MEXICO TO SHIFT EASTWARD.  THIS CHANGE IN THE
 STEERING FLOW SHOULD FORCE JIMENA TO MOVE ON A MORE NORTHWESTERLY
 COURSE BEYOND 48 HOURS.  IT SHOULD BE NOTED THAT MODEL SPREAD IS
 RATHER LARGE TOWARD THE END OF THE FORECAST PERIOD...AS MODELS
 DIFFER ON THE STRENGTH OF SUBTROPICAL RIDGE TO THE NORTH OF THE
 CYCLONE. IN ONE CAMP...THE HWRF/GFDL CONTINUE TO FAVOR LESS RIDGING
 TO THE NORTH...RESULTING IN A TRACK RIGHT OF THE MODEL CONSENSUS. 
 IN THE OTHER CAMP...THE UKMET/ECMWF/CANADIAN MODELS KEEP A MORE
 ROBUST RIDGE TO THE NORTH OF JIMENA AND THEREFORE TRACK THE CYCLONE
 MUCH FARTHER WEST.  THE OFFICIAL FORECAST TRACK IS A COMPROMISE
 BETWEEN THE TWO EXTREMES...NEARLY IN BETWEEN THE PREVIOUS PACKAGE
 AND THE UPDATED MODEL CONSENSUS.
  
 JIMENA IS FORECAST TO ENCOUNTER A LIGHT SHEAR ENVIRONMENT AND VERY
 WARM SEA SURFACE TEMPERATURES ALONG THE FORECAST TRACK OVER THE
 NEXT FEW DAYS.  THEREFORE...STRENGTHENING IS EXPECTED AND THE
 OFFICIAL FORECAST FOLLOWS THE MODEL CONSENSUS...CALLING FOR JIMENA
 TO BECOME A HURRICANE IN 36-48 HOURS.  BY 96 HOURS...JIMENA SHOULD
 BE TRAVERSING COOLER WATERS...AND A GENERAL WEAKENING IS FORECAST.
 THE OFFICIAL INTENSITY FORECAST IS SLIGHTLY HIGHER THAN THE
 SHIPS MODEL GUIDANCE BUT LOWER THAN THE GFDL/HWRF RUNS WHICH MAKE
 JIMENA A MAJOR HURRICANE.
   
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      29/0900Z 14.1N 102.3W    35 KT
  12HR VT     29/1800Z 14.4N 103.5W    40 KT
  24HR VT     30/0600Z 14.9N 104.8W    50 KT
  36HR VT     30/1800Z 15.4N 106.1W    60 KT
  48HR VT     31/0600Z 16.4N 107.3W    75 KT
  72HR VT     01/0600Z 19.5N 110.0W    80 KT
  96HR VT     02/0600Z 23.0N 112.5W    75 KT
 120HR VT     03/0600Z 25.5N 114.0W    60 KT
  
 $$
 FORECASTER KIMBERLAIN