WDPN33 PGTW 230900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (NINETEEN) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.4N 135.9E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 267 NM NORTHWEST OF YAP MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH TROPICAL DEPRESSION (TD) 19W (NINETEEN) ACCELERATING NORTHEASTWARD. DEEP CONVECTION HAS BEEN DISPLACED TO THE SOUTHWEST AS A RESULT OF STRONG GRADIENT FLOW IN WHICH THE LLCC IS CURRENTLY EMBEDDED, MULTIPLIED BY 10-15 KT VERTICAL WIND SHEAR (VWS) FROM THE NORTHEAST. ADDITIONAL ENVIRONMENTAL ANALYSIS REVEALS MARGINAL CONDITIONS FOR FURTHER DEVELOPMENT. SEA SURFACE TEMPERATURES (SST) REMAIN WARM (29-30 C) AND OUTFLOW IS ENHANCED BY A MODERATE EQUATORWARD CHANNEL. WHILE PERSISTENT TROPOSPHERIC MOISTURE IS HIGHLY CONCENTRATED WITHIN THE WESTERN QUADRANT, SIGNIFICANT DRY-AIR INTRUSION EMBEDDED TO THE EAST AND NORTHEAST CONTINUES TO ENVELOPE THE SYSTEM. STRUCTURALLY, TD 19W IS BECOMING MORE ELONGATED AS WITNESSED BY 230420Z GW1 AMSR2 MICROWAVE IMAGERY AND SUPPORTED BY AN EARLIER (230057Z) METOP-C ASCAT PASS. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON VISIBLE IMAGERY OF THE FULLY EXPOSED LLCC. THE INITIAL INTENSITY OF 30 KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON A 230230Z OSCAT PASS, AND THE AUTOMATED AND AGENCY ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTHEAST AND LOW-LEVEL SOUTHWESTERLIES AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T1.5 - 25 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 39 KTS AT 230610Z CIMSS ADT: 34 KTS AT 230610Z CIMSS AIDT: 31 KTS AT 230610Z CIMSS D-MINT: 27 KTS AT 230500Z CIMSS D-PRINT: 31 KTS AT 230640Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE EQUATORWARD OTHER FACTORS: DRY AIR ENTRAINMENT THROUGHOUT THE EASTERN SEMICIRCLE ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 19W IS CURRENTLY ACCELERATING NORTHEASTWARD, DRIVEN BY THE STEERING INFLUENCE OF A NER ANCHORED TO THE EAST- SOUTHEAST AND ENHANCED BY LOW-LEVEL SOUTHWESTERLIES. AROUND TAU 24, THE DOMINANT STEERING INFLUENCE WILL SHIFT TO A SUBTROPICAL RIDGE POSITIONED TO THE NORTHEAST, VEERING TD 19W NORTHWARD AND NORTHWESTWARD ALONG THE SUBSIDED WAKE OF TYPHOON 17W (SAUDEL). WHILE THE VWS IS EXPECTED TO REMAIN INITIALLY LOW, MODEL GUIDANCE INDICATES SIGNIFICANT UPTICK JUST PRIOR TO TAU 24, WHICH COMBINED WITH INCREASING ENTRAINMENT OF DRY AIR INTO THE CORE WILL INITIATE A WEAKENING TREND, DEPRESSING INTENSITY TO 20-25 KTS BY TAU 36. TOWARDS TAU 48, TD 19W WILL STRUGGLE TO PRESERVE ITS VERTICAL STRUCTURE AS IT ENTERS THE REGION OF SHEARED TAIL END WINDS OF TYPHOON 17W. ACCORDINGLY, COMPLETE DISSIPATION OVER OPEN WATER IS PROJECTED BY TAU 48, ALTHOUGH AN ACCELERATED DECAY TIMELINE REMAINS VIABLE SHOULD INCREASED VERTICAL WIND SHEAR AND DRY AIR ADVECTION BE MORE PRONOUNCED AS CURRENTLY MODELED. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE EXHIBITS FAIR INITIAL CONSISTENCY, EVIDENCED BY A CONSTRAINED 115 NM CROSS-TRACK SPREAD AT TAU 48, WITH ALL MAJOR GLOBAL AND MESOSCALE SYSTEMS RESOLVING COHERENT MOTION UNDER CURRENT STEERING FORCING. WHILE THE OFFICIAL JTWC TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS, CURRENT PLACEMENT IS LEANING TOWARDS THE WESTERN PROJECTION OF THE EXPERIMENTAL GOOGLE DEEPMIND GUIDANCE, WHICH HAS BEEN INITIALIZING VERY WELL OVER THE LAST 48 HOURS. IN TERMS OF INTENSITY, GFS DEPICTS A LIGHT INCREASE IN PEAK WIND SPEEDS TO 35 KTS AT TAU 12, FOLLOWED BY WEAKENING AND EVENTUAL DECAY. ALL OTHER CONSENSUS MEMBERS PREDICT STEADY WEAKENING, WITH HAFS ESTIMATING FULL DISSIPATION AS EARLY AS TAU 24. THE ONLY OUTLIER IS A GFS-DRIVEN COAMPS-TC, WHICH ESTIMATES THE SYSTEM REACHING 45-50 KTS AROUND TAU 24. OFFICIAL JTWC INTENSITY FORECAST IS LAID CLOSE TO THE MULTI-MODEL CONSENSUS AND SLIGHTLY ABOVE WIND SPEED MAXIMA PROPOSED BY HAFS GUIDANCE, WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM// NNNN