WDPN32 PGTW 100900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (NAMTHEUN) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.1N 159.6E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 420 NM WEST-SOUTHWEST OF WAKE ISLAND MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS IMPROVED CONVECTION OVER A PREVIOUSLY PARTIALLY-EXPOSED LOW LEVEL CIRCULATION (LLC). A WIDE SWATH OF FRAGMENTED FORMATIVE BANDING IS WRAPPING IN FROM THE EAST SIDE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON AN LLC FEATURE IN THE 100253Z AMSR MICROWAVE IMAGE. THE INITIAL INTENSITY OF 35KTS IS BASED WITH MEDIUM CONFIDENCE ON AN OVERALL ASSESSMENT OF AGENCY AND DVORAK ESTIMATES AND REFLECTS THE 6-HR CONVECTIVE IMPROVEMENT. ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS FOR DEVELOPMENT WITH ROBUST RADIAL OUTFLOW, LOW TO MODERATE VWS, AND WARM SSTS. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EASTERN EXTENSION OF THE LOW- TO MID-LAYER OF THE STR TO THE NORTHWEST. INITIAL WIND RADII BASIS: SCATTEROMETER DATA. CURRENT STEERING MECHANISM: EXTENSION OF THE SUBTROPICAL RIDGE (STR) TO THE NORTHWEST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS RCTP: T2.5 - 35 KTS KNES: T2.0 - 30 KTS CIMSS ADT: 33 KTS AT 100540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS NAMTHEUN WILL CONTINUE ON ITS CURRENT TRACK UP TO TAU 48. AFTERWARD, A SECONDARY STR TO THE EAST-SOUTHEAST WILL ASSUME STEERING AND DRIVE THE SYSTEM POLEWARD, CREST THE STR AXIS NEAR TAU 72, THEN RECURVE IT NORTHEASTWARD. THE FAVORABLE CONDITIONS WILL PROMOTE A STEADY INTENSIFICATION TO A PEAK OF 65KTS BY TAU 72. AFTERWARD, INCREASING VWS AND COOLING SSTS WILL GRADUALLY DECAY THE SYSTEM DOWN TO 40KTS BY TAU 120. MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE WIDEST SPREAD OF 380+ NM AT TAU 72. AEMN IS THE NOTABLE LEFT OUTLIER. IN VIEW OF THIS, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS THAT ARE ALIGNED CLOSE TO THE CONSENSUS MODELS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN