WDPN31 PGTW 110900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 25.0N 140.0E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 72 NM WEST OF IWO TO MOVEMENT PAST 6 HOURS: WESTWARD AT 04 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A QUASI-STATIONARY, NEARLY FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OF THE TROPICAL DEPRESSION (TD) 06W. RECENT FLARING CONVECTION HAS BEEN IMMEDIATELY SHEARED OFF TO THE SOUTHEAST. A 110621Z F18 SSMIS MICROWAVE IMAGE SUITE REVEALS A CONSOLIDATING STRUCTURE OF THE LOWER LEVELS, WITH ASYMMETRICAL CONVECTING BANDING AND ASSOCIATED WIND FIELD, AS ALSO ANALYZED USING A 110332Z GCOMW1 AMSR2 WIND SPEED PRODUCT. LACK OF PERSISTENT CENTRAL CONVECTION CAN BE ATTRIBUTED TO THE PRESENCE OF AN UPPER LEVEL TROUGH DIRECTLY ABOVE THE SYSTEM. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A NEARLY FULLY EXPOSED LLCC PRESENT IN THE ANIMATED VISIBLE SATELLITE IMAGERY, WHILE THE INITIAL INTENSITY OF 30 KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON THE AGENCY DVORAK FIXES, AUTOMATED AIDS LISTED BELOW, AS WELL AS A RECENT SURFACE OBSERVATION FROM IWO TO REPORTING 15-20 KTS SOUTHERLY WINDS. ADDITIONAL ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY FAVORABLE CONDITIONS WITH MODERATE TO HIGH DEEP-LAYER MOISTURE, LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM (28-29 C) SEA SURFACE TEMPERATURES, AND AN UPPER-LEVEL DIFFLUENCE REGION TO THE SOUTH AMPLIFYING EQUATORWARD PORTION OF THE OUTFLOW. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: COMPETING STEERING BETWEEN RIDGING TO THE NORTHWEST AND A WEAK SUBTROPICAL RIDGE (STR) TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T1.0 - 25 KTS KNES: T1.5 - 25 KTS CIMSS ADT: 30 KTS AT 110600Z CIMSS D-PRINT: 26 KTS AT 110610Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE EQUATORWARD OTHER FACTORS: UPPER LEVEL TROUGH LOCATED OVER THE SYSTEM 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 06W HAS RECENTLY BECOME QUASI-STATIONARY IN RESPONSE TO ITS LOCATION WITHIN A COL REGION, BETWEEN TWO AREAS OF RIDGING TO THE NORTHWEST AND NORTHEAST. AS A RESULT, TRANSLATION SPEEDS OVER THE NEXT 24-36 HOURS ARE EXPECTED TO BE LOW, WHILE THE STEERING PATTERN DEVELOPS. WHILE THE SYSTEM IS HEADING NORTH AND NORTHEASTWARD, AROUND TAU 36, RIDGING TO THE WEST IS EXPECTED TO WEAKEN AND MOVE WESTWARD, WHILE THE STR EXTENSION TO THE EAST WILL BUILD AND MOVE WESTWARD AS WELL. AS A RESULT, TD 06W IS FORECAST TO BEGIN ACCELERATING AND TRACKING NORTHWARD AROUND TAU 36, WHILE SLIGHTLY INTENSIFYING, REACHING PEAK WIND SPEEDS OF AROUND 50 KTS BY TAU 48. AT THE SAME TIME, FURTHER DEVELOPMENT WILL BE HINDERED BY DRY AIR ENTRAINMENT, EXPECTED TO START SIGNIFICANTLY IMPACTING THE CORE OF THE VORTEX. AROUND TAU 78, TD 06W WILL BEGIN INTERACTING WITH A PASSING LONGWAVE TROUGH, AND EVENTUALLY BECOME EMBEDDED WITHIN THE ASSOCIATED BAROCLINIC FLOW. EXTRATROPICAL TRANSITION IS THEREFORE FORECAST TO BEGIN SHORTLY AFTER OR AROUND TAU 72 AND COMPLETE BY TAU 96. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR AGREEMENT OVERALL, WITH ALL CONSENSUS MEMBERS AGREEING ON SLOW INITIAL SPEED OVER WATER AND A GENERALLY NORTHWARD TRACK, FOLLOWED BY A NORTHEASTWARD TURN. CROSS-TRACK SPREAD AT TAU 48 IS HOWEVER EXPANDING TO 165 NM, FROM 100 NM AT TAU 36. AFTER TAU 72, GALWEM AND UKMET ENSEMBLE BECOME THE OUTLIERS, PREDICTING A NORTHWESTWARD TURN, WHILE THE REMAINING MEMBERS OF THE MULTI-MODEL CONSENSUS AGREE ON A NORTHWARD TRACK, WITH A NORTHEASTWARD TURN SHORTLY THEREAFTER. JTWC FORECAST IS THEREFORE ASSESSED WITH MEDIUM CONFIDENCE FOR THE SHORT TERM, FOLLOWED BY LOW CONFIDENCE TOWARDS THE END OF THE CURRENT PERIOD, AND IS LAID SLIGHTLY ON THE WESTERN SIDE OF THE MULTI-MODEL CONSENSUS. MEANWHILE, THE INTENSITY GUIDANCE IS IN OVERALL FAIR AGREEMENT, WITH ALL MEMBERS PREDICTING INITIAL GRADUAL INTENSIFICATION, FOLLOWED BY WEAKENING BEGINNING AROUND TAU 60. PEAK INTENSITY SPREAD IS CURRENTLY AT 20 KTS, WITH THE DETERMINISTIC GFS BEING THE LEAST AGGRESSIVE, AND HAFS PROJECTING STRONGEST WINDS AROUND 55 KTS, NEAR TAU 60. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN