WDPN31 PGTW 170900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (RAI) WARNING NR 018// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 10.2N 119.2E INITIAL INTENSITY: 95 KTS GEOGRAPHIC REFERENCE: 278 NM SOUTH-SOUTHWEST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 26 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS BROAD AREA OF CONVECTION MOVING THROUGH THE SULU SEA. FOR A FEW FRAMES OF THE MSI LOOP, THERE APPEARED TO BE A NEW EYE TRYING TO FORM, HOWEVER, THE CONVECTIVE MASS IS NOW MORE ORGANIZED AND SURROUNDS THE MAIN LLCC. A VIVID MICROWAVE EYE FEATURE IS EASILY IDENTIFIABLE ON THE 170546Z AMSR2 36GHZ AND 89GHZ COLOR COMPOSITE IMAGES LENDING TO HIGH CONFIDENCE FOR THE INITIAL POSITION. THE INITIAL INTENSITY IS SET WITH MEDIUM CONFIDENCE AND HEDGED SLIGHTLY HIGHER THAN ADT AT 82KTS, SATCON AT 87KTS, AND IS MORE IN LINE WITH THE VAST MAJORITY OF DVORAK CURRENT INTENSITY ESTIMATES LYING BETWEEN T4.5(77KTS) AND T5.5(102KTS). ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE, WITH WARM SSTS, MODERATE EASTERLY SHEAR AND GOOD WESTWARD AND POLEWARD OUTFLOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.5 - 102 KTS RJTD: T4.5 - 77 KTS RCTP: T5.0 - 90 KTS KNES: T5.0 - 90 KTS CIMSS SATCON: 80 KTS AT 170147Z CIMSS ADT: 84 KTS AT 170540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG WESTWARD OTHER FACTORS: MODERATE POLEWARD AND EQUATORWARD OUTFLOW. 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: TY 28W HAS CONTINUED TO DEGRADE OVER THE PAST FEW HOURS, AND IS MOVING BACK OVER THE NORTHERN PORTION OF THE WARM SULU SEA. IT WILL CONTINUE TO MOVE WESTWARD OVER NORTHERN PALAWAN ISLAND. THE PASSAGE OVER PALAWAN IS EXPECTED TO HAVE LITTLE IN THE WAY OF IMPACT ON THE INTENSITY. ONCE IN THE SOUTH CHINA SEA, THE SYSTEM WILL BEGIN TO DEEPEN AND INTENSIFY AS THE SYSTEM CONTINUES MOVING WESTWARD OVER THE WARM WATERS. AN UPPER-LEVEL ANTICYCLONE IS EXPECTED TO FORM OVER THE SYSTEM, BOTH REDUCING THE VWS AND INCREASING THE AVAILABLE OUTFLOW, WHICH WILL ALSO REACH INTO THE SOUTHERN REACHES OF THE MID-LATITUDE WESTERLIES. THE INCREASED OUTFLOW AND WARM SSTS WILL HELP THE SYSTEM REACH A PEAK OF 105 KNOTS BY TAU 24. THEREAFTER, THE SYSTEM WILL THEN GRADUALLY TURN MORE NORTHWESTWARD WITH EACH PASSING HOUR AND BY TAU 48, IT WILL TURN SHARPLY POLEWARD AS IT ROUNDS THE STR AS THE RIDGE RETREATS EASTWARD. SHORTLY AFTER TAU 48, THE SYSTEM WILL ENCOUNTER COOLER SSTS AND BEGIN TO WEAKEN RAPIDLY AS THE SURGE FROM THE NORTHEAST WILL INCREASE VWS AND EXPOSE THE LOW-LEVEL CIRCULATION. THE SYSTEM WILL FULLY DISSIPATE OVER THE WATER BY TAU 120, TURNING EAST-SOUTHEASTWARD FOLLOWING THE LOW-LEVEL FLOW PATTERN SOUTHEAST OF HONG KONG. MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH TAU 72, WITH A MODEST SPREAD OF ONLY 160NM AT THIS TIME. AS THE SYSTEM RECURVES THE GUIDANCE SPREADS BUT REMAINS IN RELATIVELY GOOD AGREEMENT, WITH THE SPREAD ONLY INCREASING 20NM AT TAU 96, THEN QUICKLY INCREASING TO 280NM AT TAU 120. THE BULK OF THE GUIDANCE IS CONSTRAINED WITHIN A TIGHT ENVELOPE THROUGH THE FORECAST PERIOD, HOWEVER, JGSM LOSES THE SYSTEM OVER HAINAN, WHILE GALWEM CARRIES THE SYSTEM JUST SOUTH OF HONG KONG. THE JTWC FORECAST LIES ALONG THE NORTHERN SIDE OF THE ENVELOPE THROUGH TAU 48, THEN ON THE INSIDE OF THE RECURVE TRACK THROUGH TAU 120. CONFIDENCE IS HIGH THROUGH TAU 72, THEN LOW THEREAFTER AS THE RATE OF WEAKENING WILL HAVE A LARGE IMPACT ON THE ULTIMATE TRACK. INTENSITY GUIDANCE IS IN AGREEMENT ON THE OVERALL INTENSIFICATION AND WEAKENING TREND, BUT DEPICTS FAIRLY LARGE DIFFERENCES IN THE ACTUAL INTENSITIES. THE JTWC FORECAST CLOSELY TRACKS THE COAMPS-TC AND HWRF THROUGH TAU 48, AND THEN FALLS MORE IN LINE WITH THE CONSENSUS MEAN THROUGH THE REMAINDER OF THE FORECAST. UNCERTAINTY REMAINS HIGH THROUGH THE FORECAST, AS THE ULTIMATE INTENSITY RELIES UPON HOW QUICK THE SYSTEM WILL INTENSIFY IN THE SOUTH CHINA SEA. THUS THERE IS LOW CONFIDENCE IN THE JTWC INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN