WDIO31 PGTW 040900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (SHAKHTI) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 21.9N 64.1E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 236 NM SOUTHWEST OF KARACHI, PAKISTAN MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH COOLING UPPER- LEVEL CLOUDS TOPS THAT ARE BEGINNING TO WRAP AROUND THE LLCC IN THE SOUTHWEST QUADRANT. ENVIRONMENTAL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT, CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR, WARM (28-29C) SEA SURFACE TEMPERATURES, AND MODERATE OUTFLOW, SLIGHTLY OFFSET BY DRY AIR IN THE MID-LEVELS. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE TIGHT LOW-LEVEL WRAPPING AND THE BEGINNINGS OF AN EYE FORMING IN ANIMATED VISIBLE IMAGERY. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND OBJECTIVE INTENSITY AIDS LISTED BELOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHEASTERN PERIPHERY OF A STRONG SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHWEST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS DEMS: T3.5 - 55 KTS CIMSS ADT: 41 KTS AT 040300Z CIMSS AIDT: 37 KTS AT 040500Z CIMSS D-PRINT: 47 KTS AT 040530Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: MID-LEVEL DRY AIR ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM 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: TROPICAL CYCLONE (TC) 02A IS FORECAST TO CONTINUE ITS WEST-SOUTHWESTWARD TRACK THROUGH TAU 36 AS 02A IS INFLUENCED BY THE SOUTHEASTERN PERIPHERY OF THE PRIMARY STEERING RIDGE. BETWEEN TAUS 36-48, THE WEAKER STR OVER THE INDIAN SUBCONTINENT WILL BUILD AND EXTEND SOUTHWEST, CAUSING 02A TO STALL IN THE INCREASINGLY COMPETITIVE STEERING ENVIRONMENT. 02A IS FORECAST TO SLOWLY TURN SOUTH DURING THIS TIME, BUT MODELS ARE IN SIGNIFICANT DISAGREEMENT OVER WHEN AND WHERE THE TURN WILL OCCUR. ONCE THE TURN IS COMPLETED, AROUND TAU 48, 02A IS EXPECTED TO BE PICKED UP BY THE NOW DOMINANT STR TO ITS SOUTH AND TRACK EAST-SOUTHEASTWARD UNTIL DISSIPATION AROUND TAU 72. REGARDING INTENSITY, 02A IS EXPECTED TO INTENSIFY SLIGHTLY TO 60 KTS AT TAU 12, BEFORE BEGINNING A CONSISTENT WEAKENING TREND BETWEEN TAUS 24-72. DISSIPATION IS FORECAST TO OCCUR NO LATER THAN TAU 72, DUE TO SIGNIFICANT DRY AIR ENTRAINMENT THAT IS EXPECTED TO SMOTHER THE SYSTEM. SHEAR IS ALSO EXPECTED TO INCREASE DURING THIS TIME, TO 20-25 KTS, CONTRIBUTING TO EXPEDITED DISSIPATION. MODEL DISCUSSION: DETERMINISTIC MODELS ARE IN GOOD AGREEMENT THROUGH TAU 36, WITH ALL MODELS SHOWING A SOUTHWESTWARD TRACK. AFTERWARDS, HOWEVER, TRACK GUIDANCE DIVERGES, WITH LARGE DIFFERENCES IN THE TRACK SPEED AND HOW SHARP OF A TURN 02A WILL TAKE. NAVGEM IS THE LARGEST OUTLIER IN JTWC CONSENSUS, HOLDING 02A ON A STRAIGHT SOUTHWESTWARD TRACK UNTIL TAU 60. THE GFS ENSEMBLE MEAN FALLS IN THE OTHER EXTREME, FORECASTING 02A TO MAKE A HAIRPIN RECURVE AT TAU 36 BEFORE TRACKING DUE EAST. THE JTWC TRACK FORECAST IS MOST SIMILAR TO ECMWF AND GFS DETERMINISTIC, SLIGHTLY TO THE EAST OF THE MULTI-MODEL CONSENSUS MEAN. AS A RESULT OF THE LARGE MODEL DISCREPANCIES, THE JTWC TRACK FORECAST PLACED WITH OVERALL LOW CONFIDENCE. RELIABLE INTENSITY GUIDANCE, ON THE OTHER HAND, IS IN STRONG AGREEMENT THROUGHOUT THE FORECAST PERIOD, WITH ALL MODELS FORECASTING A PEAK AT TAU 12 BEFORE CONSISTENTLY WEAKENING, SUPPORTING THE JTWC INTENSITY FORECAST WITH OVERALL MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: LOW INTENSITY 00-72 HR: MEDIUM// NNNN