WDIO31 PGTW 092100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (BIPARJOY) WARNING NR 015// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.2N 67.4E INITIAL INTENSITY: 65 KTS GEOGRAPHIC REFERENCE: 516 NM SOUTH OF KARACHI, PAKISTAN MOVEMENT PAST 6 HOURS: NORTHWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 25 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES THAT TC 02A HAS ONCE MORE UNDERGONE A PULSE OF CONVECTIVE CONSOLIDATION, AS IT HAS EVERY DAY AT THIS TIME. HOWEVER, SHEAR HAS DROPPED OFF A NOTCH ACCORDING TO THE LATEST CIMSS ANALYSIS, WHICH HAS ENABLED THE CONVECTIVE OUTFLOW TO PUSH BACK AGAINST THE EASTERLY SHEAR VECTOR, LEADING TO THE EMERGENCE OF A WARM SPOT OR EYE FEATURE IN THE EIR. A 091724Z GMI 37GHZ MICROWAVE IMAGE REVEALED A VERY WELL-DEFINED LOW-LEVEL MICROWAVE STRUCTURE, WITH CONVECTIVE BANDING SURROUNDING THE ENTIRETY OF A WELL-DEFINED MICROWAVE EYE FEATURE. THE COLOR ENHANCED 37GHZ IMAGE ALSO REVEALED A CYAN RING SURROUNDING THE EYE, WHICH COULD BE INDICATIVE OF ADDITIONAL INTENSIFICATION IN THE OFFING. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE IMAGERY NOTED ABOVE. A 091327Z SMAP PASS REVEALED 61 KNOT 10-MIN WINDS, WHICH CONVERTS TO 66 KNOTS 1-MIN AND HENCE THE 12Z BEST TRACK HAS BEEN UPDATED TO REFLECT THIS CHANGE. THE EIR EYE FEATURE DEVELOPED AFTER THE 18Z HOUR, AND THE SUBJECTIVE INTENSITY ESTIMATES HAVE YET TO CATCH UP AND WERE CLOSER TO THE 50-55 KNOT RANGE. BASED ON THE MICROWAVE STRUCTURE AND EMERGENCE OF THE NASCENT EYE IN EIR, THE INITIAL INTENSITY IS PUSHED HIGHER THAN THE AVAILABLE ESTIMATES WITH MEDIUM CONFIDENCE, THOUGH IT REMAINS POSSIBLE THE INITIAL INTENSITY IS ACTUALLY A TAD HIGHER. THE SYSTEM LIES IN A COMPLEX ENVIRONMENT WITH FEATURES SUCH AS THE VERY WARM WATERS AND GOOD OUTFLOW TOWARDS THE WEST AND SOUTH BEING OFFSET BY THE STRONG AND PERSISTENT EASTERLY SHEAR. THE SYSTEM IS MOVING SLOWLY NORTHWARD ALONG THE WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) OVER INDIA. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.0 - 65 KTS KNES: T4.0 - 65 KTS DEMS: T4.0 - 65 KTS CIMSS SATCON: 66 KTS AT 091613Z CIMSS ADT: 53 KTS AT 091800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 31-32 CELSIUS OUTFLOW: MODERATE WESTWARD OTHER FACTORS: MODERATE EQUATORWARD OUTFLOW 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 02A IS FORECAST TO CONTINUE MOVING STEADILY BUT SLOWLY POLEWARD THROUGH THE MAJORITY OF THE FORECAST. LATE IN THE FORECAST PERIOD, SIGNIFICANT UNCERTAINTY COMES INTO PLAY AS THE GLOBAL MODELS DEPICT RADICALLY DIFFERENT OUTCOMES TO THE STEERING PATTERN, RESULTING IN A LARGE DIVERGENCE IN THE POTENTIAL TRACK. TO DATE THE ECMWF HAS BEEN THE BEST PERFORMING MODEL AND THIS MORE CREDENCE IS PLACED IN THIS SOLUTION. THUS A NORTH-NORTHEASTWARD TRACK IS ANTICIPATED THROUGH TAU 48, WITH A GRADUAL TURN MORE NORTHWARD THROUGH TAU 96 AND VERY SMALL TURN TOWARDS THE NORTHEAST AGAIN BY THE END OF THE FORECAST PERIOD. THE PRIMARY DRIVER OF THE TRACK REMAINS THE RIDGE TO THE EAST THROUGH THE BULK OF THE FORECAST, THOUGH LATE IN THE FORECAST THE RIDGE OVER INDIA SHIFTS SOUTHWARD AND A NEWLY RIDGE IS FORECAST TO BUILD OVER THE STRAIT OF HORMUZ, WHICH WILL ALLOW FOR A POSSIBLE NORTHEAST TURN AFTER TAU 96. IN TERMS OF INTENSITY, THE SYSTEM HAS CLEARLY BEEN ABLE TO PUSH BACK AGAINST THE SHEAR ONCE AGAIN, WITH DEEP CONVECTION ROTATING UPSHEAR (EAST) OF THE LLCC, ENOUGH TO ESTABLISH A WELL-DEFINED LOW-LEVEL MICROWAVE EYE AND DEVELOPING EYE IN THE EIR. THIS TIME LOOKS TO BE THE REAL-DEAL, WITH THE EMERGENCE OF THE EYE WHICH HAS TO DATE NOT BEEN SEEN. THUS, ADDITIONAL NEAR-TERM INTENSIFICATION IS FORECAST, TO A PEAK OF AT LEAST 85 KNOTS BY TAU 24, CARRYING THROUGH TO TAU 36. THEREAFTER, SHEAR IS EXPECTED TO ONCE AGAIN REAR ITS UGLY HEAD AND WHEN COMBINED WITH DECREASED OUTFLOW AND SOME CONVERGENT FLOW ALOFT, WILL LEAD TO STEADY WEAKENING THROUGH TAU 96. A SLIGHT REDUCTION IN SHEAR IS EXPECTED ONCE MORE BY THE END OF THE FORECAST, BUT OUTFLOW WILL BE TIGHTLY CONSTRICTED BY THIS POINT, LEADING TO STEADY INTENSITY THROUGH TAU 120. MODEL DISCUSSION: THROUGH TAU 72, DETERMINISTIC TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT, WITH A 150NM SPREAD, THOUGH THE FIRST HINTS OF A BIFURCATION START TO APPEAR, WITH THE UKMET BASED MODELS AND ENSEMBLES SPLITTING OFF FROM THE REST OF THE PACK AS EARLY AS TAU 48. BY TAU 120, THE NAVGEM, HWRF AND COAMPS-TC TRACKERS RACE OFF TO THE NORTHWEST, REACHING AS FAR WEST AS 62E LONGITUDE, WHILE THE UKMET AND ENSEMBLE TRACK TOWARDS THE GUJARAT PENINSULA, LEADING TO A SPREAD APPROACHING 500NM. COMPLICATING THE FORECAST IS THE CONTINUING TREND OF THE GFS, GEFS, ECMWF AND ECENS TO SHIFT OVER MORE AND MORE EASTWARD AFTER TAU 72. WITH THIS RUN, THE GFS LIES CLOSE TO THE JTWC FORECAST TRACK BUT THE ECMWF NOW TURNS SHARPLY EAST BY TAU 120, CLOSE TO THE GUJARAT PENINSULA. AS WELL A COMPARISON OF MULTIPLE ENSEMBLES (GFS, ECMWF, MOGREPS, COAMPS-TC) SHOWS A VERY WIDESPREAD BETWEEN THE ENSEMBLE MEANS, AS WELL AS WITHIN-ENSEMBLE MEMBER SPREAD, ESPECIALLY AFTER TAU 96. THE JTWC TRACK IS PLACED WITH MEDIUM CONFIDENCE THROUGH TAU 72, LOW CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS MIXED WITH THE SHIPS GUIDANCE INDICATING LITTLE TO NO CHANGE UNTIL TAU 96, WHILE THE MESOSCALE MODELS ARE ALL INDICATING NEAR-TERM INTENSIFICATION. ADDITIONALLY, SEVERAL RAPID INTENSIFICATION AIDS (RI) ARE TRIGGERING, SO CLEARLY THE MESOSCALE MODELS ARE PICKING UP ON SOMETHING HERE. HENCE THE JTWC FORECAST CALLS FOR AT LEAST 20 KNOTS OF INTENSIFICATION THROUGH TAU 24, FOLLOWED BY A SLOW WEAKENING TREND TO THE END OF THE FORECAST, WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN