WDXS32 PGTW 220300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (NINE) WARNING NR 010// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 12.0S 102.3E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 317 NM EAST OF THE COCOS ISLANDS MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL CYCLONE 09S HAS SLOWED TO A CRAWL AS IT SWITCHES STEERING FLOW IN A SPLIT SUBTROPICAL RIDGE. PREVIOUSLY, THE STORM WAS BEING DRIVEN WEST BY AN ANTICYCLONE CENTERED OVER THE PILBARA COAST, BUT YESTERDAY IT TRACKED FURTHER AWAY AND MOVED INTO A WEAKNESS BETWEEN THE TWO PARENT ANTICYCLONES, SHOWING A SUBTLE POLEWARD DRIFT. NOW, THE LAST THREE POSITIONS SHOW A BEARING OF 280-285 DEGREES AS THE SYSTEM COMES UNDER THE INFLUENCE OF THE NEW ANTICYCLONE. ANIMATED WATER VAPOR IMAGERY SHOWS THE CHANGE IN THE OUTFLOW WITH SUBSTANTIAL DRYING AND CLEARING ON THE POLEWARD SIDE OF THE SYSTEM AND THE DEVELOPMENT OF VIGOROUS OUTFLOW OVER THE EQUATORWARD SEMICIRCLE. ON THE SURFACE, THE LOW LEVEL CIRCULATION CENTER (LLCC) REMAINS TIGHTLY WRAPPED WHILE THE BULK OF THE DEEP CONVECTION HAS ALSO SHIFTED TO THE EQUATORWARD SEMICIRCLE. DURING THE PAST THREE HOURS, CONVECTION HAS INCREASED AND BEGUN CONSOLIDATING OVER THE POLEWARD SEMICIRCLE. A 212249Z GMI PASS ADDED GOOD CONFIDENCE TO THE FIX POSITION WHILE THE .60 WRAP IN TCB IS THE SAME AS YESTERDAY. OBJECTIVE ASSESSMENTS FROM CIMMS FELL SIGNIFICANTLY FROM 24 HOURS AGO AND THE 40KT INTENSITY OF THE SYSTEM BACKS OFF 5KTS FROM THE JTWC DVORAK BUT THE SMALL SIZE OF THE SYSTEM AND LATITUDE BIAS SUPPORTS STAYING CLOSER TO THE DVORAK THAN THE OBJECTIVE ASSESSMENTS. INITIAL WIND RADII BASIS: PERSISTENCE FROM AN EARLIER SAR PASS AT 211128Z. CURRENT STEERING MECHANISM: THE EQUATORWARD FLANK OF THE SUBTROPICAL RIDGE, WHICH IS ANCHORED IN AN ANTICYCLONE NEAR 17S 93S. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS DEMS: T3.0 - 45 KTS APRF: T2.5 - 35 KTS CIMSS SATCON: 47 KTS AT 211825Z CIMSS ADT: 39 KTS AT 220030Z CIMSS AIDT: 32 KTS AT 220030Z CIMSS D-MINT: 32 KTS AT 212245Z CIMSS D-PRINT: 35 KTS AT 220030Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL CYCLONE 09S WILL CRUISE SLOWLY ALONG A WESTERLY BEARING AND DEEPEN AT A LOWER THAN CLIMATOLOGICAL RATE, TOPPING OUT AT OR NEAR TYPHOON STRENGTH. THE TRACK CONTINUES TO FOCUS ON A STRIKE OR NEAR MISS ON THE COCOS ISLANDS ON CHRISTMAS DAY. TIMING OF PASSAGE AND ASPECT TO THE ISLANDS REMAIN UNCERTAIN BUT CONFIDENCE IN THE GENERAL SCENARIO IS INCREASING WITH EACH FIX AND MODEL RUN. THE STABILITY AND ORIENTATION OF THE OCEANIC RIDGE WILL NOT ALLOW FOR MUCH POLEWARD MOVEMENT AND UPSTREAM VERTICAL WIND SHEAR CONDITIONS, SEA SURFACE TEMPERATURES, AND OUTFLOW PATTERNS ARE STEADY ALONG TRACK. A MODELED SOUNDING OF THE UPSTREAM ENVIRONMENT INDICATES A MAXIMUM VERTICAL WIND SHEAR (VWS) OF 18KTS OF SOUTHEAST SHEAR IN THE MID-LEVELS AND 13KNOTS EAST-NORTHEAST IN THE TOTAL COLUMN, BUT THE WESTWARD TRACK OF THE LLCC WILL MITIGATE THE SHEAR SUBSTANTIALLY. THE PRIMARY FORCES WORKING AGAINST THIS SYSTEM CONTINUE TO BE UPWELLING AND DRY AIR ENTRAINMENT. BOTH SATELLITE AND TPW ANIMATION SHOW THE FIRST INTRUSION OF DRY AIR INTO THE CORE BEGAN YESTERDAY BETWEEN 00Z AND 18Z BUT THE SYSTEM WAS ABLE TO ABSORB IT AND HAS REGATHERED ITSELF. THERE IS MORE DRY AIR TO COME, HOWEVER, WITH MID-LEVEL MOISTURE PROGS SHOWING DRY AIR COILING AROUND THE LLCC LIKE A SNAKE AND ISOLATING THE CORE BY TAU 72. UPWELLING CAUSED BY THE SLOW MOVEMENT OF THE SYSTEM WILL BEGIN WEAKENING THE SYSTEM FROM BELOW AFTER TAU 48, PUTTING A CEILING ON SYSTEM INTENSITY. UNFORTUNATELY, THE PEAK INTENSITY OF THE SYSTEM IS EXPECTED TO OCCUR DURING THE PERIOD WHEN THE SYSTEM IS APPROACHING AND PASSING THE COCOS ISLANDS. MODEL DISCUSSION: SHORT TERM TRACK GUIDANCE HAS TIGHTENED UP SUBSTANTIALLY OVER PAST FEW CYCLES. DURING THE FIRST 36 HOURS, TRACK GUIDANCE IS LOOSE BUT CONSISTENT IN SHOWING A TRACK GENERALLY JUST SOUTH OF WEST, BUT AFTER THAT, BOTH CROSS-TRACK AND ALONG-TRACK SPREADS BECOME WIDELY SPREAD BEYOND THE POINT OF BEING ANNOYING. SOME OF THOSE WIDE GOERSS PROBABILITY CONSENSUS ERRORS (GPCE) CIRCLES ARE DUE TO THE WIDELY DISPARATE GUIDANCE FROM SOME OF THE LOWER SKILLED TRACKERS, BUT SOME OF IT IS CAUSED BY THE HAFS-A AND HWRF. BOTH OF THOSE COUPLED MODELS BREAK OFF FROM THE MAIN PACK AND TAKE A MORE WEST-SOUTHWESTERLY TRACK BEGINNING ALMOST IMMEDIATELY, SHOWING A POLEWARD DRIFT WITH A MUCH SLOWER SPEED OF ADVANCE. THE HAFS ALSO SHOWS THE HIGHEST INTENSITY OF ALL AIDS, TAKING THE STORM UP TO 85KTS NEAR TAU 48. GIVEN THAT THE SOUTHWESTWARD JAUNT IS EXPECTED TO BEGIN IMMEDIATELY AND ANY SUBSTANTIAL POLEWARD MOVEMENT WOULD BE SWIMMING UPSTREAM INTO THE SEASONAL SUBTROPICAL RIDGE, AS WELL AS THE FACT THAT THE SYSTEM HAS BEEN TRACKING DUE WESTERLY DESPITE BEING STEERED BY THE WEAKER PORTION OF THE RIDGE, THE JTWC FORECAST STAYS WITH THE MAIN PACK OF UNCOUPLED MODELS, ESPECIALLY THE EURO AND AMERICAN ENSEMBLES AND THE EC-AIFS. IF IT TURNS OUT THE HAFS AND HWRF ARE CORRECT, THAT WILL REVEAL ITSELF DURING THE NEXT 12 HOURS AND IT WILL BE A QUICK ADJUSTMENT. A TRACK THAT FOLLOWS THE ENSEMBLES WILL SUSTAIN THE THREAT TO THE COCOS ISLANDS, WHEREAS IF IT TURNS OUT THE COUPLED MODELS ARE CORRECT, THERE WILL BE LESS OF A THREAT AND MORE CERTAINTY THAT THE WINDS OVER THE COCOS ISLANDS WILL COME FROM THE WEST. THE CURRENT CLOSE CPA OF THE FORECAST TRACK MAKES WIND DIRECTION AS THE SYSTEM IS TRACKING OVER THE COCOS ISLANDS UNANSWERABLE AT THIS POINT. THE ISLANDS SIT PRETTY MUCH DEAD CENTER IN THE GOERSS PROBABILITY CONSENSUS ERROR CIRCLES AT TAU 72. THUS, THE MEDIUM AND LONG RANGE TRACK WILL USE OLD SCHOOL TECHNIQUES AND STEER THE SYSTEM WITH THE SYNOPTIC PATTERN USING A CONSTANT BEARING AND MILDLY INCREASING SPEED OF ADVANCE, FAVORING THE ENSEMBLES. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN