WDPN31 PGTW 220300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.3N 143.4E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 70 NM WEST OF NAVSTA GUAM MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) CONTINUES TO DEPICT A SHEARED COMPACT CYCLONE, WITH A LOW-LEVEL CENTER (LLC) BECOMING PARTIALLY EXPOSED ON THE WESTERN EDGE OF A MASS OF RAGGED CONVECTION. A TUTT CELL OVER THE PHILIPPINE SEA CAN BE SEEN PUSHING CIRRUS FRAGMENTS TOWARD THE LLC FROM THE WEST-SOUTHWEST, DENOTING MODERATE SOUTHWESTERLY SHEAR. DRY MID-LEVEL AIR ASSOCIATED WITH THE TUTT CELL IS STILL PREVENTING UPSHEAR PROPAGATION OF CONVECTION, EVIDENCED BY THE IMMEDIATE EVAPORATION OF NASCENT THUNDERSTORMS IN THE WESTERN SEMICIRCLE DURING THE PAST 6 HOURS. THE INITIAL POSITION AND INTENSITY ARE BOTH LARGELY BASED ON EXTRAPOLATION FROM A BULLSEYE 212214Z ASCAT METOP-A PASS INDICATING MAXIMUM WINDS OF 25- 30 KTS. OVERALL ORGANIZATION OF THE VORTEX HAS CHANGED LITTLE DURING THE PAST 6 HOURS. INITIAL WIND RADII BASIS: SCATTEROMETER DATA. 25-30KTS INDICATED ON THE BULLSEYE 212214Z ASCAT METOP-A PASS. CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T1.5 - 25 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 40 KTS AT 211840Z CIMSS ADT: 35 KTS AT 220110Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 06W WILL CONTINUE TRACKING NORTHWESTWARD AROUND THE SOUTHWESTERN PERIPHERY OF A DEEP- LAYER SUBTROPICAL RIDGE TO THE NORTHEAST, EVENTUALLY TURNING NORTHWARD BY 72 HOURS. THE SPEED WITH WHICH TD 06W ROUNDS THIS RIDGE WILL DEPEND ON HOW FAR NORTHEAST THE CYCLONE TRACKS DURING THE NEXT 48-72 HOURS, AS A MORE RIGHTWARD TRACK, WOULD PLACE THE CYCLONE CLOSER TO THE STRONG BELT OF DEEP-LAYER SOUTHERLY FLOW, LEADING TO FASTER FORWARD MOTION. NUMERICAL MODEL GUIDANCE IS THUS SPREAD BETWEEN SLOWER, LEFTWARD TRACKS AND FASTER, RIGHTWARD TRACKS. THE JTWC TRACK FORECAST LEANS SLIGHTLY TOWARD THE NUMERICAL MODEL GUIDANCE IS THUS SPREAD BETWEEN SLOWER, LEFTWARD TRACKS AND FASTER, RIGHTWARD TRACKS. THE JTWC TRACK FORECAST CONTINUES TO LEAN SLIGHTLY TOWARD THE RIGHT SIDE OF THE GUIDANCE ENVELOPE DURING THE FIRST 72 HOURS, IN PART DUE TO A SLIGHT JOG NORTH OF GUIDANCE DURING THE PAST 6 HOURS. THE JTWC TRACK FORECAST IS SLIGHTLY FASTER DURING THE 72- 120 HOUR PERIOD COMPARED TO THE PREVIOUS FORECAST, FOLLOWING THE RECENT GUIDANCE TREND, WHICH IS NOW ONLY SPREAD AT 135NM BY TAU 72. THE LARGE-SCALE ENVIRONMENT IS EXPECTED TO REMAIN ONLY MARGINALLY FAVORABLE FOR INTENSIFICATION, AS CONTINUED ENTANGLEMENT WITH THE NEARBY UPPER-LEVEL TROUGH RESULTS IN MODERATE SHEAR FOR THE NEXT 12 HOURS AND CONTINUES TO COMBAT AGAINST A DRIER AIR MASS TO THE WEST- NORTHWEST. THE SHEAR WILL BEGIN TO LESSEN OVER THE NEXT 24 TO 48 HOURS AS THE SYSTEM BEGINS TO ROUND THE RIDGE AXIS AND REACHES A PEAK INTENSITY OF 55KTS BY TAU 72. SHEAR WILL BEGIN INCREASING AGAIN AS THE CYCLONE PASSES BENEATH AN UPPER-LEVEL RIDGE AXIS. STRONG LOW- MID LEVEL SOUTHERLY FLOW BETWEEN THE STR AND MEI-YU FRONTAL BOUNDARY WILL RESULT IN MODERATE NORTHERLY SHEAR AND DECREASE THE SYSTEMS INTENSITY TO 45KTS BY TAU 96. TD 06W WILL APPROACH COOLER SSTS OF 24- 25C, WEAKEN, AND SIMULTANEOUSLY BEGIN UNDERGOING AN EXTRATROPICAL TRANSITION, AND DECREASE TO 30 KTS BY TAU 120. GIVEN THE SMALL SIZE OF THE CYCLONE THAT IS FORECAST TO PERSIST, POTENTIAL INTERACTION WITH THE MEI-YU BOUNDARY INDUCES LOWER CONFIDENCE IN THE TRACK FORECAST AFTER 72 HOURS. MODEL DISCUSSION: THE JTWC TRACK FORECAST GENERALLY LIES SLIGHTLY TO THE RIGHT AND SLOWER THAN THE MULTI-MODEL CONSENSUS, IN PART DUE TO THE LEFTWARD OUTLIERS AFUM AND UKMET ENSEMBLE WHICH DO NOT PROPERLY RESOLVE THE SMALL TROPICAL CYCLONE VORTEX, AS WELL AS THE SPEEDY OUTLIER NAVGEM. THE JTWC INTENSITY FORECAST IS SLIGHTLY BELOW THE MULTI-MODEL CONSENSUS AFTER 48 HOURS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN