WDXS32 PGTW 230300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (GRANT) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 12.6S 100.0E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 183 NM EAST OF THE COCOS ISLANDS MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL CYCLONE 09S (GRANT) WITH IMPROVED CENTRAL CONVECTION THAT IS NOW OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE LLCC IS ANALYZED TO BE UNDERNEATH THE NORTHERN PORTION OF THE CONVECTIVE MASS BASED ON THE MSI. A 222333Z WSFM 37 GHZ MICROWAVE IMAGE REVEALED A SLIGHTLY RAGGED MICROWAVE EYE FEATURE AND A DEFINED BANDING FEATURE WITHIN THE EASTERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE WSFM IMAGE. A 222224Z RCM-3 SAR IMAGE SHOWED A COMPACT WIND FIELD WITH A VMAX OF AROUND 50 KTS WITHIN THE SOUTHERN SEMICIRCLE. THE INCIDENT ANGLE OF THE SAR PASS WAS ON THE HIGHER END (OVER 55 DEGREES), CAUSING CONFIDENCE IN THE DATA TO BE HINDERED. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE COMBINATION OF THE AGENCY DVORAK AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT THE ENVIRONMENT IS NOW FAVORABLE CHARACTERIZED BY MODERATE POLEWARD OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND WARM (27-28 C) SEA SURFACE TEMPERATURES. INITIAL WIND RADII BASIS: 222224Z RCM-3 SAR DATA CURRENT STEERING MECHANISM: NORTHEASTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTHWEST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS DEMS: T3.0 - 45 KTS APRF: T3.0 - 45 KTS CIMSS SATCON: 42 KTS AT 222334Z CIMSS ADT: 45 KTS AT 230000Z CIMSS AIDT: 35 KTS AT 230000Z CIMSS D-MINT: 39 KTS AT 222335Z CIMSS D-PRINT: 40 KTS AT 230030Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE POLEWARD 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 FORECAST TO TRACK NORTHWESTWARD, ALONG THE NORTHEASTERN PERIPHERY OF THE STR TROUGH TAU 36. NEAR TAU 36, THE TRAJECTORY IS FORECAST TO BECOME MORE WESTWARD AS THE SYSTEM TRACKS ALONG THE NORTHERN PORTION OF THE SAME STR. NEAR TAU 72, ANOTHER STR IS EXPECTED TO BUILD TO THE SOUTHEAST OF 09S AT THE SAME TIME AS THE FIRST STR WEAKENS. AS A RESULT, THE PRIMARY STEERING MECHANISM WILL BECOME THE NORTHWESTERN PERIPHERY OF THE STR TO THE SOUTHEAST AND THE TRACK MOTION WILL BE WEST-SOUTHWESTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, 09S IS FORECAST TO STEADILY INTENSIFY THROUGH TAU 72 TO AROUND 70 KTS AS THE ENVIRONMENT REMAINS FAVORABLE WITH LOW SHEAR AND IMPROVING POLEWARD OUTFLOW. NEAR TAU 72, SOME DRY AIR ENTRAINMENT FROM THE NORTH IS FORECAST TO PUT A CAP ON THE INTENSIFICATION TREND, CAUSING 70 KTS TO BE MAINTAINED THROUGH TAU 120. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN RELATIVELY GOOD AGREEMENT THROUGH TAU 72, WITH THE EXCEPTION OF NAVGEM, WHICH CONTINUES TO TRACK THE SYSTEM SHARPLY SOUTHWESTWARD AFTER TAU 48. DISCOUNTING NAVGEM, THERE IS A 105 NM CROSS-TRACK SPREAD AT TAU 72 WHICH OPENS UP TO 210 NM AT TAU 120. OF NOTE, GFS AND GALWEM BOTH HAVE A WEST-NORTHWESTWARD TRACK AFTER TAU 72 WHILE ECMWF AND THE GOOGLE DEEPMIND HAVE A WEST-SOUTHWESTWARD TRACK. THE JTWC TRACK FORECAST IS PLACED WITH OVERALL MEDIUM CONFIDENCE, HEDGED CLOSER TO THE LATTER MODEL GROUPING. INTENSITY GUIDANCE IS SPLIT WITH HWRF AND GFS SUGGESTING A STAGNANT INTENSITY THROUGHOUT THE ENTIRE FORECAST PERIOD. ON THE OTHER HAND, HAFS-A AND COAMPS-TC SUGGEST INTENSIFICATION THROUGH TAU 72 AND THEN A FLAT INTENSITY THROUGH TAU 120. HAFS-A IS THE MOST AGGRESSIVE MODEL WITH A PEAK INTENSITY OF AROUND 95 KTS AT TAU 72 WHILE COAMPS-TC (GFS BASED) IS AROUND 60 KTS. THE JTWC INTENSITY FORECAST IS PLACED HIGHER THAN THE CONSENSUS, MORE IN LINE WITH HAFS-A AND COAMPS-TC, WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN