000
WTPZ43 KNHC 292033
TCDEP3
HURRICANE JIMENA DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP132009
200 PM PDT SAT AUG 29 2009
 
VISIBLE SATELLITE IMAGES SHOW THAT JIMENA HAS A SMALL CENTRAL DENSE
OVERCAST...ALONG WITH IMPRESSIVE BANDING FEATURES TO THE NORTH AND
SOUTH OF THE CENTER. HOWEVER...DURING THE PAST COUPLE OF HOURS THE
TINY EYE HAS BECOME LESS DISTINCT WITH SOME WARMING OF THE
THUNDERSTORM CLOUD TOPS.  SATELLITE CLASSIFICATIONS HAVE BEEN
PLAYING CATCH UP ALL DAY...NOW 90 KT FROM BOTH TAFB/SAB...AND THIS
WILL BE THE INITIAL INTENSITY. THE ONLY FORESEEABLE WAY THAT JIMENA
WOULD STOP INTENSIFYING DURING THE NEXT DAY OR SO IS AN EYEWALL
CYCLE...WHICH IS A POSSIBILITY GIVEN THE SMALL EYE AND A MOAT OF
DRIER AIR SEEN ON MICROWAVE IMAGERY.  OTHERWISE...ALL ENVIRONMENTAL
CONDITIONS FAVOR THE DEVELOPMENT OF A POWERFUL CATEGORY FOUR
HURRICANE DUE TO EXTREMELY WARM WATERS...AS MUCH AS 1.5C WARMER
THAN AVERAGE...AND LOW SHEAR.  IT IS NOTABLE THAT JIMENA WILL BE
TRAVERSING THE WARMEST WATERS IN THE BASIN OVER THE NEXT 48
HOURS...WHICH HAVE BEEN UNTAPPED BY TROPICAL CYCLONES SO FAR THIS
SEASON.  THE NHC FORECAST IS FAIRLY CLOSE TO A BLEND OF THE LGEM AND
THE SHIPS MODEL...AND SHOWS ANOTHER RAPID INTENSIFICATION PERIOD
DURING THE FIRST 24 HOURS.  WEAKENING SHOULD COMMENCE IN ABOUT
2-3 DAYS DUE TO COOLING WATERS AND PERHAPS AN INCREASE IN SHEAR.
 
THE FORMATION OF THE EYE HAS LED TO A MORE RELIABLE INITIAL MOTION
OF 300/10...TO THE RIGHT OF THE PREVIOUS ESTIMATE.  A MOTION
BETWEEN WEST-NORTHWEST AND NORTHWEST IS LIKELY FOR THE NEXT COUPLE
OF DAYS AS THE HURRICANE IS STEERED AROUND THE SOUTHWESTERN PORTION
OF A WEAK MID-LEVEL RIDGE OVER MEXICO.  THE HURRICANE AND GLOBAL
MODELS ARE STILL IN A LARGE DISAGREEMENT OVER HOW MUCH A MID- TO
UPPER-LEVEL TROUGH OVER BAJA CALIFORNIA WILL EFFECT JIMENA.  THE
RIGHT SIDE OF THE GUIDANCE ENVELOPE CONSISTS OF THE GFDL/HWRF...
WHICH INSISTS THAT JIMENA WILL TURN TO THE NORTH-NORTHWEST TOMORROW
AND THREATEN BAJA CALIFORNIA OR WESTERN MEXICO. ALL OF THE OTHER
GUIDANCE MAINTAIN ENOUGH OF A RIDGE BETWEEN THE TROUGH AND JIMENA
TO CONTINUE A NORTHWESTWARD MOTION OF THE HURRICANE FOR SEVERAL
DAYS...KEEPING JIMENA FARTHER AWAY FROM MEXICO.   ALTHOUGH THE
HWRF/GFDL HAVE HISTORICALLY HAD AN EASTWARD BIAS FOR THESE TYPES OF
SYSTEMS...THE GLOBAL MODELS HAVE GENERALLY MADE A SMALL EASTWARD
ADJUSTMENT IN THEIR 1200 UTC FORECASTS.  THE NHC FORECAST IS
SHIFTED A LITTLE TO THE RIGHT OF THE PREVIOUS ONE...BETWEEN THE
MODEL CONSENSUS AND THE GLOBAL MODELS.  THIS FORECAST HAS TO BE
CONSIDERED LOW CONFIDENCE DUE TO THE BIG DIFFERENCES BETWEEN THE
HWRF/GFDL AND THE REST OF THE GUIDANCE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/2100Z 15.1N 104.2W    90 KT
 12HR VT     30/0600Z 15.6N 105.3W   105 KT
 24HR VT     30/1800Z 16.3N 106.6W   120 KT
 36HR VT     31/0600Z 17.2N 107.8W   125 KT
 48HR VT     31/1800Z 18.3N 109.0W   125 KT
 72HR VT     01/1800Z 21.0N 111.5W   110 KT
 96HR VT     02/1800Z 24.0N 114.5W    80 KT
120HR VT     03/1800Z 25.5N 118.0W    50 KT
 
$$
FORECASTER BLAKE