WDIO31 PGTW 101500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (BIPARJOY) WARNING NR 018// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.3N 67.4E INITIAL INTENSITY: 90 KTS GEOGRAPHIC REFERENCE: 451 NM SOUTH OF KARACHI, PAKISTAN MOVEMENT PAST 6 HOURS: NORTHWARD AT 03 KTS SIGNIFICANT WAVE HEIGHT: 33 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: AS THE SUN SETS OVER THE ARABIAN SEA, THE FINAL FRAMES OF ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN INCREASINGLY EXPOSED LOW LEVEL CIRCULATION WHICH IS THE RESULT OF PERSISTENT AND BUILDING UPPER LEVEL EASTERLY SHEAR. TIGHTLY WRAPPING LOW LEVEL CLOUD LINES CAN BE SEEN IN THE EASTERN SEMICIRCLE OF THE LLCC PROVIDING SOME AID TO LOCALIZATION. A RECENT 101133Z SSMIS 91GHZ MICROWAVE IMAGE INDICATES A CONVECTIVELY ASYMMETRIC CIRCULATION WITH A BULK OF THE DEEP CONVECTION LIMITED TO THE SOUTHERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI AND VERY RECENT SSMIS IMAGERY. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON PGTW DVORAK INTENSITY ESTIMATE ALONGSIDE CIMMS D-PRINT WHICH BOTH SHOW 87-90KTS WHILE THE REMAINING GUIDANCE IS SLIGHTLY AND IN THE CASE OF ADT SIGNIFICANTLY LOWER. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTH AND THE WESTERN PERIPHERY OF A NORTH-SOUTH ORIENTED RIDGE OVER WESTERN INDIA. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.0 - 90 KTS KNES: T4.5 - 77 KTS DEMS: T4.5 - 77 KTS CIMSS SATCON: 81 KTS AT 100836Z CIMSS ADT: 61 KTS AT 101200Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 30+ KTS SST: 31-32 CELSIUS OUTFLOW: MODERATE WESTWARD 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 REMAIN ON A GENERALLY NORTHWARD TRAJECTORY THROUGH TAU 72, AFTER WHICH THE BULK OF THE GUIDANCE INDICATES AN EASTWARD TURN, WHILE A FEW REBELS STILL SHIFT WESTWARD. CURRENTLY IN A MARGINAL ENVIRONMENT CHARACTERIZED BY MODERATE UPPER LEVEL OUTFLOW AND WARM SEA SURFACE TEMPERATURES GENERALLY OFFSET BY PERSISTENT AND BUILDING UPPER LEVEL WIND SHEAR. THROUGH TAU 24, 02A MAY ACHIEVE LIMITED GROWTH BUT WILL LIKELY SIMPLY STAVE OFF WEAKENING IF IT CAN REMAIN CONVECTIVELY COHESIVE. AFTER TAU 24 HOWEVER, PERSISTENT VERTICAL WIND SHEAR NOW JOINED BY RAPIDLY DETERIORATING OUTFLOW ALOFT WILL GRADUALLY WEAKEN THE SYSTEM THROUGH THE REMAINING FORECAST PERIOD. THE FORECAST TRACK IS ANOTHER MATTER ENTIRELY. AS THE SYSTEM PROGRESSES POLEWARD, THE CROSS-TRACK SPREAD AND ALONG-TRACK SPREAD IN MODEL SOLUTIONS CANNOT BE OVERSTATED. OVER THE PAST FEW CYCLES, THE RUN TO RUN VARIABILITY HAS IMPROVED BUT TWO DISTINCT OUTCOMES ARE STILL EVIDENT PAST TAU 72. THE EXISTENCE AND STRENGTH OF A STR THAT SETS UP OVER THE GULF OF OMAN AND THE RIDGING OVER SOUTHERN INDIA ARE PIVOTAL TO THE LONG TERM TRACK DIRECTION OF 02A. THE BULK OF CURRENT DEEP LAYER MEAN MODEL GUIDANCE FAVORS THE GULF OF OMAN STR AND WEAKER RIDGING OVER SOUTHERN INDIA ALLOWING THE SYSTEM TO SLIP POLEWARD AND EASTWARD. MODEL DISCUSSION: AS DISCUSSED ABOVE, NUMERICAL MODELS ARE INITIALLY IN FAIR AGREEMENT AND IN POOR AGREEMENT THEREAFTER. NVGM AND COMAP-TS (NVGM VERSION) ARE THE SOLE MEMBERS THAT TRACK WESTWARD WHILE GFS, HWRF, ECMWF AND THEIR ENSEMBLE CURVE THE SYSTEM EASTWARD AFTER TAU 72 TOWARD NEW DELHI. FOR THIS REASON THE INITIAL FORECAST TRACK IS PLACED WITH MEDIUM CONFIDENCE AND WITH LOW CONFIDENCE THEREAFTER. RELIABLE MODEL INTENSITY GUIDANCE IS IN FAIR AGREEMENT WITH ALL MEMBERS SHOWING MARGINAL INTENSIFICATION AFTER WHICH A GRADUAL WEAKENING WITH THE EXCEPTION OF COAMPS-TC WHICH INDICATES ANOTHER ROUND OF INTENSIFICATION THROUGH TAU 12 AND GRADUAL WEAKENING THEREAFTER. FOR THESE REASONS THE JTWC INTENSITY FORECAST IS PLACED WITH OVERALL 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