WDXS32 PGTW 300300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (GRANT) WARNING NR 026// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 14.3S 78.3E INITIAL INTENSITY: 110 KTS GEOGRAPHIC REFERENCE: 551 NM SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 33 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL CYCLONE (TC) 09S (GRANT) WITH A RELATIVELY COMPACT CONVECTIVE STRUCTURE AND AN OBSERVABLE PINHOLE EYE-FEATURE, WHICH HAS BECOME INCREASINGLY OBSCURED OVER THE LAST FEW HOURS. PERSISTENT DEEP CONVECTION HAS ALSO CONTINUED TO WRAP NEATLY AROUND THE CENTRAL VORTEX OVER THE LAST FEW HOURS. ALOFT, WEAK RADIAL OUTFLOW HAS BECOME THE PRIMARY UPPER-LEVEL SUPPORT MECHANISM, OBSERVABLE ON ANIMATED WATER VAPOR IMAGERY. THE INITIAL POSITION HAS BEEN PLACED WITH HIGH CONFIDENCE BASED ON THE 292244Z 91 GHZ SSMIS IMAGE AND ANIMATED MSI. THE INITIAL INTENSITY HAS BEEN ASSESSED WITH MEDIUM CONFIDENCE BASED ON SUBJECTIVE AGENCY DVORAK ESTIMATES AND CIMSS AUTOMATED INTENSITY ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE LOCATED DIRECTLY TO THE SOUTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.5 - 102 KTS DEMS: T5.5 - 102 KTS FMEE: T5.5 - 102 KTS FIMP: T6.0 - 115 KTS CIMSS SATCON: 107 KTS AT 292007Z CIMSS ADT: 107 KTS AT 300000Z CIMSS AIDT: 100 KTS AT 300100Z CIMSS D-MINT: 117 KTS AT 292244Z CIMSS D-PRINT: 103 KTS AT 300030Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 27-28 CELSIUS OUTFLOW: WEAK RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 09S IS FORECASTED TO TRACK WESTWARD THROUGHOUT THE NEXT 72 HOURS, ALONG THE NORTHERN PERIPHERY OF THE SUBTROPICAL RIDGE LOCATED DIRECTLY TO THE SOUTH. AFTER TAU 72, TC 09S IS EXPECTED TO GAIN A NORTHWESTWARD TRACK UNTIL THE END OF THE FORECAST PERIOD AS A SECOND SUBTROPICAL RIDGE BUILDS NORTHWESTWARD INTO NORTHERN MADAGASCAR. REGARDING INTENSITY, TC GRANT IS FORECASTED TO SLOWLY WEAKEN IN INTENSITY OVER THE NEXT 96 HOURS AS UPPER-LEVEL OUTFLOW SUPPORT BEGINS TO DECREASE. WHILE THIS OCCURS, VERTICAL WIND SHEAR IS ALSO EXPECTED TO INCREASE TO NEAR 20 KTS BY TAU 72, WHILE DRY AIR ENTRAINS INTO THE SYSTEMS STRUCTURE, LENDING CREDENCE TO THE MINIMUM INTENSITY OF 60 KTS BY TAU 96. FOLLOWING TAU 96, TC 09S IS FORECASTED TO RE-INTENSIFY TO 70 KTS BY TAU 120, AS AN EQUATORWARD OUTFLOW CHANNEL DEVELOPS, VERTICAL WIND SHEAR BECOMES MINIMAL (LESS THAN 10 KTS), AND THE CORE RE-MOISTENS. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE REMAINS IN GOOD AGREEMENT INTO TAU 48, WITH A CROSS-TRACK SPREAD OF 125 NM. FOLLOWING TAU 48, THE SHIFT IN PRIMARY STEERING MECHANISMS BEGIN TO EXTEND THE CROSS-TRACK SPREAD, HOWEVER, ALL MODEL TRACK GUIDANCE SUGGESTS A GENERALLY WESTWARD TRACK INTO TAU 48 AND TAU 72, WITH A NORTHWESTWARD TRACK THEREAFTER. WITH AN EQUAL PART OF NUMERICAL MODEL TRACK SOLUTIONS PLACED NORTH AND SOUTH OF THE JTWC CONSENSUS, THE JTWC TRACK FORECAST IS POSITIONED IN CLOSE PROXIMITY TO THE JTWC CONSENSUS ENVELOPE, LENDING HIGH CONFIDENCE FOR THE TRACK FORECAST INTO TAU 48, AND MEDIUM CONFIDENCE THEREAFTER. REGARDING INTENSITY, ALL MODEL INTENSITY SOLUTIONS ILLUSTRATE A STEADY WEAKENING PHASE INTO TAU 72. FOLLOWING TAU 72, EACH SOLUTION AGREES ON A STEADY RE-INTENSIFICATION PHASE INTO THE END OF THE FORECAST PERIOD. THE JTWC INTENSITY FORECAST HAS BEEN ALIGNED WITH THE MULTI-MODEL CONSENSUS, LENDING MEDIUM CONFIDENCE TO THE INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN