WDPN31 PGTW 211500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR 03// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 12.1N 145.3E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 99 NM SOUTH-SOUTHEAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 10 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SOMEWHAT DISORGANIZED SYSTEM, STILL STRUGGLING TO CONSOLIDATE UNDER PERSISTENT SOUTHERLY SHEAR. THE MOST RECENT MICROWAVE PASS FROM 210831Z SHOWED THE SHEARED NATURE OF THE SYSTEM AT THAT TIME, WITH CONVECTION SHEARING IN A LINEAR FORMATION TO THE NORTHEAST OF THE LOW LEVEL CIRCULATION CENTER (LLCC). HOWEVER, EIR SUBSEQUENT TO THE 1200Z HOUR CONFIRM ANOTHER FLARE UP OF DEEP CONVECTION NEAR OR OVER THE ASSESSED LLCC, BUT IT REMAINS TO BE SEEN IF THIS WILL BE MAINTAINED IN LIGHT OF THE SOUTHERLY SHEAR WHICH HAS BEEN INHIBITING DEVELOPMENT THUS FAR. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANALYSIS OF THE OUTER LOW-LEVEL BANDS EVIDENT IN THE SHORTWAVE INFRARED IMAGERY, AS WELL ANIMATED RADAR VELOCITY AND REFLECTIVE DATA FROM ANDERSEN AFB. THE INITIAL INTENSITY REMAINS AT 30 KTS, ASSESSED WITH MEDIUM CONFIDENCE BASED ON PGTW AND KNES DVORAK ESTIMATES OF T2.0, AND ADT ESTIMATE OF T2.2. ADDITIONALLY, THE RADAR VELOCITY ESTIMATES INDICATED WINDS OF 35-40 KTS AT APPROXIMATELY 10,000 FEET, WHICH PROVIDES GOOD SUPPORT FOR A 30 KT SURFACE WIND. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: DEEP LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 36 KTS AT 210903Z CIMSS ADT: 32 KTS AT 211140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM 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 06W IS FORECAST TO CONTINUE TRACKING WEST- NORTHWEST, SLOWLY TURNING STEADILY MORE NORTHWARD THROUGH TAU 72, AS IT TRAVERSES THE SOUTHWESTERN PERIPHERY OF THE DEEP STR CENTERED FAR TO THE NORTHEAST. FORWARD TRACK SPEED IS EXPECTED TO SLOW AFTER TAU 24 AS THE SYSTEM MOVES INTO A SLIGHTLY WEAKER STEERING PATTERN ON APPROACH TO THE RIDGE AXIS. TD 06W IS EXPECTED TO ROUND THE RIDGE AXIS SHORTLY AFTER TAU 72, AND THEN WILL STEADILY ACCELERATE NORTHEASTWARD THROUGH THE END OF THE FORECAST PERIOD. AS THE SYSTEM MOVES NORTH OF THE 30TH PARALLEL, IT WILL BEGIN TO INTERACT WITH THE MEIYU BOUNDARY, AND AN UPPER-LEVEL MAJOR SHORTWAVE TROUGH MOVING SOUTH OVER JAPAN AND BEGIN TO TRANSITION TO AN EXTRATROPICAL SYSTEM. IN THE NEAR-TERM, AS THE SYSTEM CONTINUES TO STRUGGLE WITH THE LOW TO MODERATE SOUTHERLY SHEAR AND SOME WEAKLY SUBSIDENT FLOW TO THE WEST, IT IS EXPECTED TO MAINTAIN TROPICAL DEPRESSION STRENGTH WHILE PASSING SOUTH OF GUAM. AFTER TAU 12, AS THE UPPER-LEVEL OUTFLOW ENVIRONMENT IMPROVES AND THE TRACK TAKES IT OVER WARMER AND HIGHER OHC WATERS, TD 06W IS EXPECTED TO INTENSIFY AT ROUGHLY THE CLIMATOLOGICAL RATE, PEAKING AT 50 KTS AT TAU 72 THROUGH TAU 96. THEREAFTER, INCREASING VWS COMBINED WITH DECREASING SSTS WILL CONSPIRE TO INDUCE STEADY WEAKENING THROUGH THE REMAINDER OF THE FORECAST PERIOD. MODEL DISCUSSION: DYNAMIC MODEL GUIDANCE REMAINS IN RELATIVELY GOOD AGREEMENT, AT LEAST THROUGH TAU 72, WITH THE CENTER OF TD 06W PASSING SOUTH OF GUAM WITH A SPREAD OF 63 NM AT TAU 24, INCREASING TO 110NM BY TAU 48. THE JTWC TRACK LIES ON THE POLEWARD SIDE OF THE GUIDANCE ENVELOPE THROUGH TAU 36, CONSISTENT WITH THE PREVIOUS SIX HOUR TRACK MOTION. FOR THE REMAINDER OF THE FORECAST PERIOD, THE JTWC TRACK REMAINS CONSISTENT WITH THE PREVIOUS TRACK THROUGH TAU 72, THEN BECOMES SLIGHTLY FASTER AND EAST OF THE MULTI-MODEL CONSENSUS MEAN. GUIDANCE SPREAD INCREASES TO OVER 800 NM BY TAU 120 AS THE ECMWF AND PARTICULARLY THE NAVGEM TRACKERS DEPICT AN UNREASONABLE ACCELERATION IN THE FORWARD TRACK SPEED, WHILE THE UKMET ENSEMBLE DEPICTS A MUCH SLOWER TRACK, FARTHER TO THE WEST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN