WDXS31 PGTW 071500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03S (THREE) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 10.3S 85.2E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 777 NM EAST-SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: SOUTHWARD AT 04 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A DISORGANIZED REGION OF PERSISTENT CONVECTIVE ACTIVITY DISPLACED TO THE SOUTHEAST OF A LOW LEVEL CIRCULATION CENTER (LLCC) WHICH IS OBSCURED BY CONVECTIVE BLOWOFF. THE EIR ALSO DEPICTS A NEW REGION OF FLARING CONVECTION TO THE EAST OF THE LLCC WHICH HAS BLOOMED OVER THE PAST SEVERAL HOURS BUT REMAINS DISORGANIZED. A 071128Z SSMIS 37GHZ MICROWAVE IMAGE DEPICTED A COMPACT LOW EMISSIVITY REGION SUGGESTIVE OF THE LLCC, WITH RELATIVELY SHALLOW CONVECTIVE BANDS WRAPPING INTO THIS CENTER FEATURE, PARTICULARLY IN THE SOUTHERN HEMISPHERE OF THE SYSTEM. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THIS MICROWAVE FEATURE. A LACK OF RECENT WINDSPEED MEASUREMENTS MEANS THE INITIAL INTENSITY IS BASED SOLELY ON AVAILABLE AGENCY AND OBJECTIVE INTENSITY ESTIMATES AND THUS IS ASSESSED WITH MEDIUM CONFIDENCE. ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY FAVORABLE, WITH WARM SSTS AND SLIGHTLY WEAKER VWS BEING OFFSET BY STRONG DIVERGENT POLEWARD OUTFLOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS KNES: T3.0 - 45 KTS FMEE: T2.5 - 35 KTS CIMSS SATCON: 40 KTS AT 070751Z CIMSS ADT: 33 KTS AT 071145Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 03S IS DRIFTING RATHER AIMLESSLY THIS MORNING, WITH AN OVERALL TREND TOWARDS THE SOUTH BUT FORWARD MOTION IS VERY SLOW SO IT REMAINS TO BE SEEN IF THIS OVERALL TRACK WILL CONTINUE. GENERALLY THE TRACK IS EXPECTED TO FIRM UP ON A SOUTHWARD HEADING OVER THE NEXT 12 HOURS OR SO AS THE WESTERN SIDE OF THE STEERING RIDGE TO THE EAST IS ERODED BY AN APPROACHING TROUGH, GENERATING A MORE NORTH TO SOUTH ORIENTED STEERING FRONT. THE SYSTEM WILL SLIDE SOUTH-SOUTHEASTWARD, PICKING UP SPEED ALONG THE WAY, OVER THE NEXT 48 HOURS. SHEAR HAS ALREADY STARTED TO WEAKEN A BIT, CURRENTLY ASSESSED AT 10-15 KNOTS, AND AS THE SYSTEM MOVES FURTHER SOUTHWARD AND APPROACHES THE AXIS OF THE 200MB RIDGE, SHEAR WILL BRIEFLY SLACKEN EVEN MORE. THE DECREASED SHEAR AND CONTINUED STRONG POLEWARD OUTFLOW SHOULD ALLOW FOR A BRIEF WINDOW OF OPPORTUNITY IN WHICH THE SYSTEM CAN INTENSIFY. BUT THIS WINDOW WILL CLOSE QUICKLY. BY TAU 48, A 500MB TROUGH WILL MOVE IN FROM THE WEST, USHERING IN INCREASED NORTHWESTERLY SHEAR AND MID-LEVEL DRY AIR, WHICH WILL LEAD TO A RAPID DECOUPLING OF THE VORTEX. SIMULTANEOUSLY THE SYSTEM WILL MOVE ACROSS THE 26C ISOTHERM INTO A REGION OF VERY LOW HEAT CONTENT, DEPRIVING IT OF ITS ENERGY SOURCE AND LEADING TO RAPID WEAKENING. AS THE SYSTEM WEAKENS AND THE STEERING LEVEL LOWERS, IT WILL TURN SHARPLY TO THE WEST AS A TRANSITORY ANTICYCLONE PASSING TO THE SOUTH BECOMES THE DOMINANT STEERING INFLUENCE. THE SYSTEM IS EXPECTED TO DISSIPATE AS A TROPICAL CYCLONE NO LATER THAN TAU 96, AND POTENTIALLY AS EARLY AS TAU 72. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN OVERALL AGREEMENT ON THE GENERAL SCENARIO BUT DOES SHOW SOME ALONG TRACK SPREAD BEGINNING AS EARLY AS TAU 36, INCREASING THROUGH THE INFLECTION POINT AT TAU 48 AND THEN AGAIN AFTER THE SYSTEM TURNS TO THE WEST. THE NAVGEM AND GALWEM MODELS ARE THE MOST SIGNIFICANT OUTLIERS, TAKING THE SYSTEM MUCH FURTHER TO THE SOUTH INTO THE RIDGE, WHICH IS CONSIDERED HIGHLY UNLIKELY. THE REMAINDER OF THE GUIDANCE CONCURS ON A SHARP TURN TO THE WEST AT OR NEAR TAU 60, THOUGH THERE IS A FAIR AMOUNT OF CROSS-TRACK SPREAD AT THIS POINT, INDUCED BY THE FACT THAT THE MODELS VARY IN HOW FAR THE SYSTEM PENETRATES TO THE SOUTH BEFORE THE TURN. THE JTWC TRACK LIES JUST WEST OF THE CONSENSUS MEAN, NEAR THE ECMWF SOLUTION WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH ALL MODELS CONSTRAINED WITHIN A TIGHT 10-KNOT ENVELOPE THROUGH THE FORECAST PERIOD. THE JTWC FORECAST LIES ALONG THE MEAN FOR THE DURATION OF THE FORECAST WITH HIGH CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: HIGH// NNNN