WDPN32 PGTW 072100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SIXTEEN) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.4N 146.2E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 253 NM NORTH OF SAIPAN MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL STORM (TS) 16W WITH DEEP BURSTS OF CONVECTION ALONG THE SOUTHERN SEMICIRCLE MEASURING -82 C AT THE COLDEST CLOUD TOPS. THE WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) HAS MOVED SLIGHTLY NORTH OF THE DEEP CONVECTION, AND HAS BECOME PARTIALLY EXPOSED. ENVIRONMENTAL ANALYSIS INDICATES THAT 16W IS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE EQUATORWARD OUTFLOW ALOFT, LOW (10-15 KTS) NORTHEASTERLY VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. THERE IS SOME APPARENT SOUTHWARD TILT WITH HEIGHT OF THE VORTEX IN RESPONSE TO THE NORTHEASTERLY SHEAR ACTING ON THE SYSTEM. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND OBJECTIVE INTENSITY ESTIMATES ALL RANGING FROM AROUND 30-35 KTS. INITIAL WIND RADII BASIS: PERSISTENCE FROM THE 071150Z METOP-C ASCAT IMAGE CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 36 KTS AT 071500ZZ CIMSS ADT: 37 KTS AT 071800Z CIMSS AIDT: 35 KTS AT 071800Z CIMSS D-MINT: 28 KTS AT 071746Z CIMSS D-PRINT: 28 KTS AT 071800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE EQUATORWARD OTHER FACTORS: VORTEX TILTED SOUTHWARD WITH HEIGHT ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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 16W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE THROUGH TAU 36. AFTER TAU 36, THE SUBTROPICAL RIDGE IS EXPECTED TO BUILD AND EXTEND ALL THE WAY TO EASTERN CHINA. THIS WILL CAUSE THE TRAJECTORY TO BE MORE WESTWARD THROUGH TAU 96 AS THE SYSTEM TRACK ALONG THE SOUTHERN PORTION OF THE EXTENSION OF THE RIDGE. AFTER TAU 96, 16W WILL TRACK MORE WEST-NORTHWESTWARD AS THE LARGE DEEP-LAYER RIDGE SHIFTS AND ANCHORS ITSELF OVER SOUTHERN HONSHU. REGARDING INTENSITY, 16W IS FORECAST TO STEADILY INTENSIIFY THROUGH TAU 72 TO AROUND 80 KTS AS THE ENVIRONMENT REMAINS FAVORABLE. NEAR TAU 72, SOME ENHANCED UPPER-LEVEL EASTERLIES WILL CAUSE VERTICAL WIND SHEAR TO INCREASE AND CAUSE THE SYSTEM TO TEMPORARILY STOP INTENSIFYING. AFTER TAU 96, THE UPPER-LEVEL EASTERLIES WILL WEAKEN, AND ALLOW FOR 16W TO FURTHER INTENSIFY THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. OF NOTE, A FURTHER NORTHWARD TRACK WILL CAUSE 16W TO EXPERIENCE MORE SHEAR, AND THEREFORE, BE WEAKER. IF THE WESTWARD TRACK IS MORE SOUTH, ALONG THE 20TH LATITUDE, SHEAR COULD HAVE LESS IMPACTS ON THE SYSTEM, ALLOWING FOR MORE INTENSIFICATION. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT WITH THE EXCEPTION OF THE NAVGEM AND UKMET DETERMINISTIC TRACKERS, WHICH TRACK THE VORTEX MUCH FURTHER POLEWARD AFTER TAU 48 THAN THE REMAINDER OF GUIDANCE. TAKING THE TWO OUTLIERS OUT, THERE IS A 110 NM CROSS-TRACK SPREAD AT TAU 72, WHICH OPENS UP TO 170 NM AT TAU 120. THE JTWC TRACK FORECAST IS PLACED WITH OVERALL MEDIUM CONFIDENCE, IN LINE WITH THE BULK OF GUIDANCE. INTENSITY GUIDANCE CONTINUES TO BE IN POOR AGREEMENT WITH AN 80 KNOT SPREAD AT TAU 72. GLOBAL MODELS CONTINUE TO BE CONSIDERABLY WEAKER THAN THE MESOSCALE MODELS. COAMPS-TC REMAINS THE MOST AGGRESSIVE MODEL, SUGGESTING A PEAK OF 115 KTS, WHILE HAFS-A AND HWRF ARE AROUND 75-85 KTS. THE JTWC INTENSITY FORECAST IS PLACED CLOSER TO THE HAFS-A AND HWRF DEPICTION WITH LOW CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN