WDPN33 PGTW 140300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (NANMADOL) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 22.7N 140.4E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 135 NM SOUTH-SOUTHWEST OF IWO TO MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 03 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CONTINUING IMPROVEMENT OF LOW LEVEL BANDING WRAPPING INTO A DEEPENING LOW LEVEL CIRCULATION CENTER (LLCC), WITH A BROADENING PLUME OF FLARING DEEP CONVECTION CONSISTENT WITH A MONSOON DEPRESSION. A 132143Z SSMIS 91GHZ IMAGE REVEALS A LARGE FEEDER BAND WRAPPING ALONG THE SOUTHERN PERIPHERY INTO WHAT IS STILL AN ILL-DEFINED CENTER. NO RECENT SCATTEROMETRY HAS BEEN AVAILABLE TO ASSIST IN LOCATING THE CENTER AND TO CONFIRM THE CURRENT INTENSITY. THE INITIAL POSITION IS PLACED BASED ON MULTI-AGENCY MSI-BASED FIX POSITIONS FROM PGTW, KNES, AND RJTD WITH MEDIUM CONFIDENCE. THE INITIAL INTENSITY WAS UPGRADED TO 40 KNOTS BASED ON DVORAK ESTIMATES OF T2.5 FROM ALL AGENCIES, AND ACCOUNTING FOR THE OVERALL IMPROVEMENT IN THE SATELLITE DEPICTION, WITH THE LATEST CIMSS SATCON VALUE COMING IN AT 41 KNOTS. ENVIRONMENTAL FACTORS ARE INCREASINGLYFAVORABLE FOR FURTHER DEVELOPMENT WITH LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS), AND WARM (29-30) SEA SURFACE TEMPERATURES (SSTS). OUTFLOW IS STILL PRIMARILY CONSTRAINED TO EQUATORWARD CHANNELS DUE TO POSITIONING OF THE SUBTROPICAL RIDGE TO THE NORTH INHIBITING THE POLEWARD FLOW. CIMSS TPW PRODUCT INDICATES CROSS-EQUATORIAL INFLOW IS PROVIDING AMPLE INFLUX OF DEEP TROPICAL MOISTURE. BASED ON LIMITED AVAILABLE DATA, TS 16W CONTINUES TO SLOWLY DRIFT EAST-NORTHEASTWARD UNDER A WEAK STEERING ENVIRONMENT. INITIAL WIND RADII BASIS: AMSR2 WINDS CURRENT STEERING MECHANISM: WEAK STEERING DUE TO COMPETING MECHANISMS AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 44 KTS AT 132204Z CIMSS ADT: 39 KTS AT 132340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 0-10 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG EQUATORWARD OTHER FACTORS: DEEP TROPICAL MOISTURE INFLOW ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: HIGH INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: THE SUBTROPICAL STEERING RIDGE (STR) TO THE NORTH IS EXPECTED TO BUILD, ALLOWING TS 16W TO FINALLY MAKE A TURN TO WEST-NORTHWEST OVER THE NEXT 12 HOURS. THIS STR SHOULD REMAIN THE PRIMARY STEERING MECHANISM OVER THE COURSE OF THE FORECAST, WITH GENERALLY NORTHWESTWARD MOTION PERSISTING UNTIL TAU 72. BETWEEN TAU 72 TO 96, A REORIENTATION OF THIS STR SHOULD DEFLECT THE TRACK WITH A MORE NORTHERLY COMPONENT, TAKING NANMADOL VERY CLOSE TO THE ISLANDS OF MINAMI DAITO JIMA AND AMAMI OSHIMA BEFORE BEGINNING TO ROUND THE STR. THE PREVIOUS FORECAST CYCLE SAW SOME ODD OUTLIER TRACKS IN THE CONSENSUS, RAISING THE POSSIBILITY OF A MORE WESTWARD TRACK INTO THE EAST CHINA SEA. THE LATEST CYCLE HAS THE AIDS COMING BACK INTO BETTER AGREEMENT WITH THE REST OF THE PACKAGE, ALL INDICATING A RECURVE SCENARIO. AT TAU 96, THERE IS ONLY 86 NM OF ACROSS TRACK SPREAD. ADDITIONALLY, THE NUMBER OF ENSEMBLE MEMBERS WITH A WESTWARD EXTENDED TRACK ALSO WENT DOWN THIS CYCLE. THE FORECAST INTENSITY TREND WAS MAINTAINED CLOSE TO THE PRIOR CYCLE, REFLECTING CONTINUED SIGNS OF RAPID DEVELOPMENT IN THE SHORT TERM. WHILE AGGRESSIVE, THE FORECAST INTENSITY TREND ALSO CONSIDERED THE LARGE SIZE OF THIS SYSTEM, WHICH SHOULD LIMIT POTENTIAL FOR EXPLOSIVE DEEPENING. THAT SAID, WITH AMPLE 29 TO 30 DEGREE C SSTS AND LOW VWS IN ITS PATH, THE PEAK FORECAST INTENSITY OF 100 KNOTS AT TAU 72 IS BASED LARGELY ON MODEL GUIDANCE FROM GFS, HWRF, AND COAMPS-TC ENSEMBLE. VERTICAL WIND SHEAR AND DECREASING SST AT THE FINAL POSIT SHOULD RESULT IN A SLOW WEAKENING TREND AT THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: AS NOTED, THE 18Z GFS CAME INTO BETTER AGREEMENT WITH THE REST OF THE MULTI-MODEL CONSENSUS. LIKEWISE, THE 18Z ECMWF TRACK (AVAILABLE THROUGH TAU 96) INDICATES THIS MODEL IS ALSO NOW IN GENERAL AGREEMENT. BEYOND TAU 96, THE PICTURE IS STILL MURKY, WITH DIFFERENCES IN THE TIMING AND POSITION OF RECURVATURE MORE PRONOUNCED (SPREAD IS 218 NM). THE TRACK WAS PLACED CLOSE TO THE PRIOR FORECAST AND SLIGHTLY WEST OF THE CONSENSUS MEAN, WEIGHTING TOWARDS THE GFS AND EURO SOLUTIONS. WHILE THE FORECAST TAKES TS NANMADOL TOWARDS THE KOREAN STRAIGHT, A SHARPER TURN TOWARDS KYUSHU IS STILL A DISTINCT POSSIBILITY. THE TIMING AND LATITUDE OF NANMADOLS TURN BACK TO THE WEST COULD AFFECT THE ULTIMATE LONG RANGE POSITING. ONCE THE TURN IS MADE, THERE SHOULD BE BETTER CLARITY IN THE MODELS. UNTIL THEN, THERE IS LOW CONFIDENCE IN THE EXTENDED FORECAST TRACK. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN