WDPN32 PGTW 240300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (NINE) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.1N 124.9E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 416 NM SOUTH-SOUTHWEST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: NOW TROPICAL STORM (TS) 09W (NINE) CONTINUES TO QUICKLY CONSOLIDATE UNDER FAVORABLE ENVIRONMENTAL CONDITIONS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY COMPACT SYSTEM, WITH DEEP CONVECTION IN THE FORM OF VORTICAL HOT TOWERS (VHTS) DEVELOPING PRIMARILY IN THE SOUTHERN HEMISPHERE OF THE ROTATION, HAVING YET TO WRAP TO THE UPSHEAR SIDE OF THE CIRCULATION. CLOUD TOP TEMPERATURES APPROACHING -87C ARE SEEN IN THE STRONGEST VHTS NEAR THE ASSESSED CENTER POSITION, INDICATORS OF THINGS TO COME. A 232132Z SSMIS 91GHZ IMAGE SHOWED LOW-LEVEL BANDING FEATURES TO THE NORTH, WITH BANDS OF DEEPER CONVECTION ACROSS THE SOUTHERN SECTORS, WRAPPING INTO A DEVELOPING LOW LEVEL CIRCULATION CENTER (LLCC), BUT AT THAT TIME, THE CONVECTION WAS STILL SPOTTY AND DISORGANIZED. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE, USING THE SPIRAL BAND ANALYSIS OF THE VISIBLE LOW-LEVEL CLOUD LINES TO THE NORTH AND EXTRAPOLATION OF THE MICROWAVE CENTER IN THE IMAGE DENOTED ABOVE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, IN LINE WITH THE KNES T2.5 DVORAK CURRENT INTENSITY ESTIMATE, SUPPORTED BY THE CIMSS DPRINT ESTIMATE OF 33 KNOTS. CIMSS ANALYSIS SUGGESTS MODERATE (17 KNOTS) NORTHERLY SHEAR, BUT THE ANIMATED WATER VAPOR IMAGERY AND THE FACT THAT THE VHTS ARE FIRING NEAR THE CENTER ARGUES FOR A LOWER VALUE. IN ADDITION TO THE LOW SHEAR, THE ENVIRONMENT IS NEARLY PERFECT WITH VERY WARM (30-31C) SSTS, VERY HIGH OHC (110 KJ PER CM2), GOOD EQUATORWARD OUTFLOW AS WELL AS SOME WEAK POLEWARD OUTFLOW AND A DEVELOPING POINT SOURCE OVER TOP OF THE SYSTEM. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T1.5 - 25 KTS KNES: T2.5 - 35 KTS CIMSS ADT: 26 KTS AT 232340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 30-31 CELSIUS OUTFLOW: MODERATE EQUATORWARD OTHER FACTORS: WEAK POLEWARD OUTFLOW, LOW TO POSSIBLY MODERATE NORTHERLY SHEAR ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: NO SIGNIFICANT CHANGES TO THE TRACK, HOWEVER THE INTENSITY FORECAST HAS BEEN INCREASED SHARPLY, WITH THE MAXIMUM INTENSITY NOW SET AT 120 KNOTS. FORECAST DISCUSSION: TS 09W CONTINUES TO TRACK TOWARDS THE NORTHWEST BASED ON THE LATEST ANALYSIS, ALONG THE WESTERN SIDE OF A DEEP-LAYER STR ANCHORED TO THE EAST. THE SYNOPTIC SETUP HAS NOT CHANGED MUCH SINCE THE PREVIOUS FORECAST, WITH THE STR TO THE EAST AND A DEVELOPING RIDGE TO THE WEST OVER THE NORTHERN PORTION OF THE SOUTH CHINA SEA. TS 09W IS FORECAST TO CONTINUE TO TRACK TOWARDS THE NORTHWEST THROUGH TAU 12 BEFORE BECOMING QUASI-STATIONARY AROUND TAU 24, AS THE STEERING PATTERN RAPIDLY MODIFIES. FIRST, THE STR TO THE EAST RAPIDLY WEAKENS AND UP AND DISAPPEARS BY TAU 30; SECOND, A VERY LARGE UPPER-LEVEL GYRE PATTERN SETS UP IN THE PHILIPPINE SEA TO THE SOUTH OF JAPAN; LASTLY THE RIDGE CURRENTLY DEVELOPING IN THE NORTHERN SCS QUICKLY STRENGTHENS AND MOVES TO THE VICINITY OF HONG KONG. THE COMBINATION OF THESE CHANGES IN THE STEERING PATTERN WILL RESULT IN A TS 09W MAKING A SHARP EQUATORWARD TURN BY TAU 36 AS IT RIDES THE RIGHT GRADIENT BETWEEN THE STR TO THE WEST AND THE GYRE TO THE EAST. BY TAU 96, THE PATTERN SHIFTS ONCE MORE, WITH THE GYRE DISSIPATING AND THE LAST REMNANTS OF IT BEING SQUEEZED OUT TO THE NORTH BY AN IMPRESSIVE STR BUILDING TO THE EAST OF JAPAN AS WELL AS A SECONDARY RIDGE OVER KYUSHU. BY TAU 108, THESE RIDGES WILL DOMINATE THE MAJORITY OF THE NORTHWESTERN PACIFIC AND BY TAU 120 THE SYSTEM WILL BEGIN TURNING POLEWARD ONCE MORE. IN TERMS OF INTENSITY, THIS FORECAST IS INTRODUCES A SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST. ENVIRONMENTAL CONDITIONS, WITH THE EXCEPTION OF A MARGINAL AMOUNT OF SHEAR, ARE NEAR PERFECT FOR RAPID INTENSIFICATION (RI). ALL AVAILABLE GUIDANCE SUGGESTS THE SHEAR WILL BACK OFF OVER THE NEXT 12 HOURS AND THE SYSTEM WILL TAP INTO A ROBUST EASTWARD OUTFLOW CHANNEL INTO THE BASE OF THE DEVELOPING GYRE, WHICH WILL ALLOW FOR THE CORE TO RAPIDLY CONSOLIDATE AND KICK OFF RI. THE FORECAST CALLS FOR RAPID AND STEADY INTENSIFICATION TO A PEAK OF 120 KNOTS BY TAU 72. AT THAT POINT THE SYSTEM BECOMES NEARLY QUASI-STATIONARY AS IT REACHES ITS EQUATORWARD INFLECTION POINT, AND WILL SUFFER FROM COLD-WATER UPWELLING AS WELL AS LIKELY EYEWALL REPLACEMENT CYCLES (ERC), INTRODUCING SLIGHT WEAKENING THROUGH THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: TRACK GUIDANCE, WHILE GENERALLY STILL IN RELATIVELY GOOD AGREEMENT, HAS STARTED TO DISPLAY INCREASING DIVERGENCE. THE UKMET ENSEMBLE CONTINUES TO MARK THE WESTERN OUTLIER, INSISTING ON TAKING THE SYSTEM OVER LUZON, BUT THE NAVGEM HAS NOW JOINED THE REST OF THE PACK, REPLACED BY THE INTERMEDIATE ECMWF AS THE EASTERN OUTLIER. THE REMAINDER OF THE CONSENSUS PACKAGE IS IN TIGHT AGREEMENT ON THE SOUTHWARD TRACK TO TAU 72, BUT DIVERGES IN THE TIMING AND STRENGTH OF THE TURN POLEWARD BEYOND THIS POINT. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST, AND LIES NEAR THE MULTI-MODEL CONSENSUS. CONFIDENCE IS MEDIUM THROUGH TAU 72, THEN LOW THEREAFTER DUE TO UNCERTAINTY IN THE ULTIMATE IMPACT OF THE GYRE AND THE DURATION OF THE QUASI-STATIONARY PERIOD AFTER TAU 72. INTENSITY GUIDANCE HAS COME INTO BETTER AGREEMENT, WITH ALL MEMBERS OF THE CONSENSUS, EXCEPT THE DECAY SHIPS (NAVGEM), INDICATING RI. THE RI45, RICN AND FRIA RI AIDS CONTINUE TO TRIGGER, AND THE HAFS-A AND CTCX DETERMINISTIC INTENSITY TRACKERS LIKE RIGHT IN LINE WITH THE RI GUIDANCE. ADDITIONALLY THE CTCX ENSEMBLE PROBABILISTIC RI FORECAST CALLS FOR 95 PERCENT LIKELIHOOD OF RI BETWEEN TAU 36 TO TAU 60. THUS THE JTWC FORECAST EXPLICITLY CALLS FOR RI STARTING AT TAU 12, FROM 45 KNOTS TO 120 KNOTS BY TAU 72. THE BULK OF THE GUIDANCE ALSO SUPPORTS THE STAGNATION OR WEAKENING AFTER TAU 72, WITH ADDITIONAL INTENSIFICATION AFTER THE END OF THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: MEDIUM// NNNN