WDPN31 PGTW 290900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (KOTO) WARNING NR 019// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.3N 112.0E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 269 NM SOUTHEAST OF DA NANG, VIETNAM MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM 33W (KOTO) WITH A MOISTENING CORE COMPARED TO 6 HOURS AGO AND BURSTS OF DEEP CONVECTION FORMING NEAR THE PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC). A 290617Z AMSR2 36 GHZ MICROWAVE IMAGE REVEALED A PARTIAL MICROWAVE EYE FEATURE WITH PROMINENT CONVECTIVE BANDING WITHIN THE NORTHERN PERIPHERY. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AMSR2 MICROWAVE IMAGE. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 33W IS IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD AND EQUATORWARD OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, UPWELLING, AND SLIGHT DRY MID-LEVEL AIR WITHIN THE EASTERN SEMICIRCLE. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: WEAK STEERING PATTERN WITH RIDGING TO BOTH THE EAST AND WEST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T3.5 - 55 KTS RCTP: T3.0 - 45 KTS KNES: T3.0 - 45 KTS DEMS: T3.0 - 45 KTS CIMSS SATCON: 44 KTS AT 290556Z CIMSS ADT: 33 KTS AT 290600Z CIMSS AIDT: 30 KTS AT 290600Z CIMSS D-MINT: 41 KTS AT 290556Z CIMSS D-PRINT: 33 KTS AT 290600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 26-27 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: UPWELLING DUE TO SLOW MOVEMENT OVER THE PAST 24 HOURS ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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: 33W IS FORECAST TO DRIFT NORTHWARD THROUGH TAU 36 AS RIDGING SLOWLY BUILDS OVER LUZON. AFTER TAU 36, THE SYSTEM IS FORECAST TO TURN SOUTHWESTWARD AS THE PRIMARY STEERING MECHANISM SWITCHES TO A SUBTROPICAL RIDGE POSITIONED TO THE WEST. A SOUTHWESTWARD TRACK IS THEN EXPECTED TO CONTINUE THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. LANDFALL IS CURRENTLY FORECAST TO OCCUR BETWEEN TAU 72 AND 96 ALONG THE COAST OF VIETNAM. 33W WILL THEN TRACK INLAND, TOWARD SOUTHEASTERN CAMBODIA THROUGH TAU 120. REGARDING INTENSITY, 33W IS FORECAST TO MARGINALLY INTENSIFY OVER THE NEXT 36 HOURS AS POLEWARD OUTFLOW SLIGHTLY IMPROVES AND SHEAR REMAINS LOW. AFTER TAU 36, SOUTHEASTERLY SHEAR AND DRY AIR ENTRAINMENT BEGINS TO INCREASE. AS A RESULT, 33W IS FORECAST TO WEAKEN AS IT APPROACHES THE COAST OF VIETNAM. 33W WILL THEN WEAKEN OVER LAND WITH DISSIPATION FORECAST TO OCCUR NO LATER THAN TAU 120. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN WORSE AGREEMENT THIS RUN COMPARED TO THE PREVIOUS MODEL RUN. GDM AND EC-AIFS BOTH TRACK THE VORTEX MUCH FURTHER NORTH THROUGH TAU 72 THAN THE REMAINDER OF GUIDANCE. ALL OTHER MODELS TURN THE SYSTEM WESTWARD AROUND TAU 48. ADDITIONALLY, AFTER TAU 72, GDM AND EC-AIFS BOTH CHECK MARK THE VORTEX TOWARD THE SOUTHWEST, KEEPING IT OVER WATER. CROSS-TRACK SPREAD AT TAU 120 IS AROUND 440 NM, CAUSING THE JTWC TRACK FORECAST TO BE PLACED WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS ALSO SPLIT WITH COAMPS-TC ANS GFS SUGGESTING INTENSIFICATION THROUGH TAU 36 TO 60-70 KTS. ON THE OTHER HAND, HAFS-A AND HWRF BOTH WEAKEN THE SYSTEM FROM TAU 0 ONWARD. THIS SPLIT IN GUIDANCE CAUSES THERE TO BE OVERALL LOW CONFIDENCE IN THE JTWC INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN