WDPN31 PGTW 201500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (OMAIS) WARNING NR 033// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.2N 129.5E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 448 NM SOUTH-SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT TD 16W HAS DEVELOPED A CENTRAL COLD COVER (CCC) TYPE FEATURE OVER THE PAST SIX HOURS. CLOUD TOP TEMPERATURES WITHIN THE CCC HAVE DROPPED SIGNIFICANTLY, WITH THE MAJORITY OF THE CONVECTIVE TOPS NEAR -75C WITH A FEW OVERSHOOTING TOPS BELOW -80C. THIS IS BASICALLY THE SAME PATTERN SEEN OVER THE PAST COUPLE OF DAYS DURING THE LOCAL OVERNIGHT HOURS. THE DEVELOPMENT OF THE SYMMETRICAL CCC IS INDICATIVE OF A DECREASE IN OVERALL SHEAR, AND THE HWRF MODEL SKEW-T INDICATES THE MID-LEVEL SHEAR HAS ALSO DECREASED AND BECOME ALIGNED WITH THE DEEP-LAYER SHEAR VECTOR, ALL ALLOWING FOR AN IMPROVEMENT IN CORE STRUCTURE. A 201040Z ASCAT-A PASS PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION, IN THE NORTHWESTERN CORNER OF THE CCC. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE, SUPPORTED BY THE ASCAT-A PASS, AND IN LINE WITH AGENCY DVORAK ESTIMATES AND SLIGHTLY BELOW THE ADT ESTIMATE. THE ASCAT PASS DID SHOW SOME HIGHER WINDS OF 35 KNOTS IN NARROW BAND TO THE SOUTHEAST OF THE CENTER, IN THE STRONGEST GRADIENT, WHILE THE WINDS IN THE REMAINDER OF THE EASTERN HEMISPHERE WERE NEAR 25 KNOTS AND LESS THAN 15 KNOTS ACROSS THE WESTERN HEMISPHERE. THE FORWARD MOTION HAS SLOWED SIGNIFICANTLY AND JOGGED TO THE WEST OVER THE PAST SIX HOURS, AS THE LOW TO MID-LEVEL HOLDS FAST TO THE NORTH. CONSISTENT WITH THE PREVIOUS ANALYSIS, A SHARP UPPER-LEVEL TROUGH LIES ALONG A LINE FROM SOUTHERN HONSHU TO THE LUZON STRAIGHT, WITH STRONG NORTHEASTERLY FLOW BEHIND IT. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: EXTENSION OF THE DEEP SUBTROPICAL RIDGE (STR) CENTERED EAST OF HONSHU. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.0 - 30 KTS KNES: T1.5 - 25 KTS CIMSS ADT: 34 KTS AT 201150Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK RADIAL 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. HOWEVER THE TRACK SHIFTS WEST BY APPROXIMATELY 60 NM. FORECAST DISCUSSION: TD 16W HAS TAKEN A TURN TO THE WEST AND SLOWED DOWN OVER THE PAST SIX HOURS AS AN EXTENSION OF THE STR REMAINS FIRMLY ENTRENCHED TO THE NORTH. THE OVERALL TRACK PHILOSOPHY HAS NOT CHANGED, BUT THE SYSTEM IS NOT EXPECTED TO TURN POLEWARD UNTIL AFTER THE RIDGE TO THE NORTH WEAKENS, WHICH IS FORECAST TO OCCUR OVER THE NEXT 24 HOURS. IN THE MEANTIME, THE SYSTEM IS EXPECTED TO TRACK WEST-NORTHWEST, WHILE GRADUALLY TURNING MORE NORTHWARD THROUGH TAU 48. IT IS EXPECTED TO ROUND THE RIDGE AXIS JUST AFTER TAU 48, AND THEN RAPIDLY ACCELERATE NORTHEASTWARD ALONG THE TIGHT GRADIENT BETWEEN THE STR AND AN APPROACHING TROUGH. DEPENDING ON THE EXACT TIMING OF THE WEAKENING OF THE RIDGE TO THE NORTH, IT IS POSSIBLE THE TRACK MAY MOVE FURTHER TO THE WEST. AS DISCUSSED, THE OVERALL ENVIRONMENT HAS IMPROVED WITH SLACKENING SHEAR AND CONTINUED RADIAL OUTFLOW. THE SYSTEM IS CURRENTLY MOVING INTO AN AREA OF HIGH OHC, WHICH IS MORE OF A FACTOR NOW THAT IT HAS SLOWED. THE OVERALL CONDUCIVE ENVIRONMENT IS EXPECTED TO CONTINUE FOR ANOTHER 24 HOURS, ALLOWING THE SYSTEM TO INTENSIFY TO A PEAK OF 40 KNOTS BY TAU 24. CONDITIONS WILL RAPIDLY DETERIORATE AFTER TAU 36 AS THE SYSTEM MOVES UNDER STRONG NORTHEASTERLY FLOW ALOFT AND EXPERIENCES RAPIDLY INCREASING VWS AND CONVERGENCE ALOFT, AND BEGIN TO WEAKEN AS IT CROSSES THE RYUKUS. ONCE IT TURNS NORTHEASTWARD, THE COMBINATION OF PERSISTENT STRONG WESTERLY FLOW ALOFT AND COOL SSTS WILL LEAD TO DISSIPATION BETWEEN TAUS 72 AND 96. MODEL DISCUSSION: TRACK GUIDANCE REMAINS SPLIT INTO TWO DISTINCT CAMPS, WITH NAVGEM, GALWEM AND UKMET ENSEMBLE TRACKING CLOSELY TOGETHER WELL TO THE SOUTH, OVER ISHIGAKIJIMA AND NOT TURNING NORTHEAST UNTIL JUST EAST OF SHANGHAI. THE REMAINDER OF THE CONSENSUS MODELS INCLUDING EGRR, GFS, ECMWF AND THEIR ENSEMBLES ARE TIGHTLY CLUSTERED ABOUT THE JTWC FORECAST TRACK THROUGH TAU 48, WITH INCREASING ALONG TRACK SPREAD THEREAFTER. THE JTWC FORECAST LIES ALONG THE SOUTHERN EDGE OF THE THIS GROUPING THROUGH TAU 36, THEN SHIFTS TO FOLLOW MOST CLOSELY THE GFS THROUGH THE REMAINDER OF THE FORECAST PERIOD. OVERALL CONFIDENCE IS LOW THROUGHOUT THE FORECAST, DUE TO THE UNCERTAINTY SURROUNDING THE NEAR-TERM MOTION VECTOR THROUGH TAU 36, THEN THE ALONG TRACK SPREAD IN THE EXTENDED TAUS. INTENSITY GUIDANCE IS FAIRLY CONSISTENT, WITH HWRF CONTINUING TO BE THE HIGH END OUTLIER, WITH THE REMAINDER OF THE CONSENSUS MEMBERS CLUSTERED AROUND A PEAK OF 40 TO 45 KNOTS, BUT ALL MODELS HOLD THE INTENSITY ABOVE 40 KNOTS UNTIL AFTER TAU 84, WHICH IS HIGHLY UNLIKELY. THE JTWC FORECAST CLOSELY TRACKS THE SHIPS-GFS GUIDANCE, JUST BELOW THE CONSENSUS MEAN THROUGH TAU 36 THEN WELL BELOW ALL GUIDANCE THEREAFTER. OVERALL CONFIDENCE IN THE INTENSITY FORECAST IS MEDIUM THROUGH THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN