WDPN33 PGTW 132100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (NANMADOL) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 22.5N 140.2E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 151 NM SOUTH-SOUTHWEST OF IWO TO MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 03 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) AND CIRA PROXY VISIBLE SATELLITE IMAGERY DEPICTS PARTIALLY EXPOSED LOW LEVEL BANDING WRAPPING INTO AN IMPROVING LOW LEVEL CIRCULATION CENTER (LLCC), WITH A BROAD PLUME OF FLARING DEEP CONVECTION TRAILING TO THE SOUTHWEST. IN THE HOURS SINCE ANALYSIS TIME, CONVECTION HAS STEADILY BEEN BUILDING OVER THE NORTHWEST QUADRANT, FURTHER EVIDENCE THAT TS NANMADOL IS COMING TOGETHER. A 131837Z GMI 36GHZ IMAGE REVEALS FORMATIVE BANDING STRUCTURES ALONG THE SOUTHERN SEMI-CIRCLE WRAPPING INTO AN LOOSELY DEFINED CENTER, WITH FRAGMENTED BANDING STRUCTURE IN THE SUBSIDENT DRY AIR TO THE NORTH AND WEST. NO RECENT SCATTEROMETRY HAS BEEN AVAILABLE TO ASSIST IN LOCATING THE CENTER AND TO CONFIRM THE CURRENT INTENSITY. DUE TO THE CDO OBSCURATION AND POORLY DEFINED MICROWAVE CENTER, THE INITIAL POSITION IS PLACED BASED ON MULTI-AGENCY FIX POSITIONS FROM PGTW, KNES, AND RJTD WITH LOW CONFIDENCE. THE INITIAL INTENSITY WAS UPGRADED TO 35 KNOTS BASED ON DVORAK ESTIMATES OF T2.5 FROM ALL AGENCIES. OBJECTIVE ADT AND SATCON ARE 43 KNOTS. ENVIRONMENTAL FACTORS ARE INCREASINGLY FAVORABLE FOR FURTHER DEVELOPMENT WITH LOW (10-15 KTS) 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. TS 16W CONTINUES TO SLOWLY TRACK EAST-NORTHEASTWARD UNDER A WEAK STEERING ENVIRONMENT, ALTHOUGH THE SLOWDOWN IN THE MOST RECENT FIXES SUGGESTS THE EXPECTED TURN BACK TO THE NORTHWEST MAY COMMENCE SOON. INITIAL WIND RADII BASIS: ASSESSED BASED ON STRONG CONVECTION IN SOUTHEAST QUADRANT CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 42 KTS AT 131614Z CIMSS ADT: 43 KTS AT 131740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM 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: THE SUBTROPICAL RIDGE TO THE NORTH IS EXPECTED TO BUILD, ALLOWING TS 16W TO MAKE A TURN TO WEST-NORTHWEST OVER THE NEXT 12 TO 24 HOURS. THIS STR SHOULD REMAIN THE PRIMARY STEERING MECHANISM OVER THE COURSE OF THE FORECAST, WITH GENERALLY NORTHWESTWARD MOTION PERSISTING UNTIL AFTER TAU 72. AFTER THIS TIME, THE SYSTEM SHOULD BEGIN TO ROUND THE RIDGE, TURNING MORE NORTHWARD AS A RESULT. THE FORECAST INTENSITY TREND WAS UPDATED TO BE MORE AGGRESSIVE IN THE SHORT TERM IN RESPONSE TO THE IMPROVING SATELLITE DEPICTION, AND ACCOUNTING FOR A NUMBER OF RAPID INTENSIFICATION (RI) AIDS THAT ARE NOW INDICATING A HIGH LIKELIHOOD OF RI. THE PEAK INTENSITY WAS SET TO 100 KNOTS AT TAU 72, 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. IT SHOULD BE NOTED THAT THE LATEST GUIDANCE FROM GFS AND ECMWF IN PARTICULAR ARE SUGGESTING A TRACK FURTHER WESTWARD IN THE EXTENDED RANGE. GFS IN PARTICULAR, MAY BE INTERACTING WITH A MID-LEVEL LOW THAT FORMS OVER EASTERN CHINA. THE FORECAST TRACK WAS SHIFTED SLIGHTLY TO THE SOUTH AND WEST, BUT STILL ASSUMING THE RECURVE PHILOSOPHY AS PREVIOUSLY ESTABLISHED. MODEL DISCUSSION: GFS AND ECMWF ARE THE PRIMARY GUIDANCE TAKING THE MORE WESTWARD TRACK IN THEIR RESPECTIVE DETERMINISTIC SOLUTIONS. THE ENSEMBLE GUIDANCE SUGGESTS AN APPROXIMATE 15 TO 20 PERCENT PROBABILITY OF THIS SCENARIO. A STRONG TYPHOON, AS PREDICTED BY RELIABLE GUIDANCE, SHOULD FAVOR THE EROSION OF THE STR, RESULTING IN THE FORECAST RECURVATURE. 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 FORECAST TRACK. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN