WDPN32 PGTW 040300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (FIVE) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.7N 118.7E INITIAL INTENSITY: 25 KTS GEOGRAPHIC REFERENCE: 296 NM EAST-SOUTHEAST OF HONG KONG MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY CONSOLIDATING, ALTHOUGH STILL SOMEWHAT DISORGANIZED CIRCULATION, WITH POCKETS OF DISORGANIZED CONVECTIVE ACTIVITY ACROSS THE SOUTHERN PORTION OF THE CIRCULATION. CONVECTION HAS MANAGED TO PERSIST THROUGH THE DIURNAL MAXIMUM AND IS IN FACT, STRENGTHENING AFTER SUNRISE, A SURE SIGN OF STEADY CONSOLIDATION OF THE SYSTEM. THE LATEST MICROWAVE PASS, A 032042Z SSMIS 37GHZ IMAGE, REVEALED THAT THE LLCC REMAINS SOMEWHAT BROAD, WITH CURVED BANDS OF CONVECTION BEGINNING TO DEVELOP TO THE SOUTH OF THE ASSESSED CENTER, THOUGH CONVECTIVE ACTIVITY ON THE NORTH SIDE REMAINS BENIGN DUE TO SOME LINGERING DRY AIR. ANIMATED MSI SUGGESTS A POSSIBLE NASCENT VORTEX ABOUT 60NM TO THE SOUTHEAST OF THE ASSESSED POSITION. THIS IS LIKELY THE MID-LEVEL VORTEX, WHICH MULTIPLE MESOSCALE MODELS SHOW AS PRECESSING AROUND THE EASTERN SIDE OF THE LLCC AND THEN EVENTUALLY MERGING INTO IT. THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE BASED ON THE DISORGANIZED NATURE OF THE LLCC AND THE LACK OF CONSISTENT HIGH-RESOLUTION MICROWAVE OR SCATTEROMETER DATA. THE INITIAL INTENSITY IS ALSO ASSESSED WITH LOW CONFIDENCE, CONSISTENT WITH THE PGTW DVORAK AND DPRINT ESTIMATES. THE ENVIRONMENT IS FAVORABLE FOR INTENSIFICATION, ONCE THE VORTEX ALIGNS, WITH WARM SSTS, AND LOW VWS. CURRENTLY, THE SYSTEM IS TAPPING INTO DUAL OUTFLOW CHANNELS, ONE TOWARDS THE EQUATOR AND ANOTHER TOWARDS THE EAST, ALONG THE SOUTHERN PART OF AN EAST-WEST ORIENTED TUTT OVER TAIWAN EXTENDING TO A TUTT-CELL SOUTHEAST OF OKINAWA. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED NEAR SHANGHAI. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T1.0 - 25 KTS KNES: T2.5 - 35 KTS CIMSS D-PRINT: 26 KTS AT 040000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE DUAL-CHANNEL OTHER FACTORS: DUAL-CHANNEL OUTFLOW EQUATORWARD AND EASTWARD. ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: LOW INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TD 05W IS CURRENTLY DRIFTING SLOWLY ON A GENERAL WESTWARD TRACK ALONG THE SOUTH SIDE OF A LARGE STR CENTERED NEAR SHANGHAI. OVER THE NEXT 12 TO 24 HOURS, THE LOW-LEVEL VORTEX IS LIKELY TO TRACE AND ERRATIC TRACK, LOOPING TO THE SOUTH AS IT PRECESSES AND UNDERGOES AN AXISYMMETRIZATION WITH THE MID-LEVEL VORTEX. HOWEVER, IN THE AGGREGATE, THE CENTER WILL CONTINUE TO TRACK TOWARDS THE WEST-NORTHWEST AT A SLOW RATE OF SPEED. AFTER TAU 24, THE SYSTEM WILL TAKE A HARD RIGHT TURN AS THE STR TO THE NORTH PUSHES NORTHEASTWARD INTO THE YELLOW SEA AND THE STR CENTERED IN THE PHILIPPINE SEA BECOMES THE DOMINANT STEERING MECHANISM. OVER THE REMAINDER OF THE FORECAST PERIOD, THE STR TO THE SOUTHEAST MOVES WEST, WHILE THE RIDGE TO THE NORTH PUSHES EAST OVER KOREA RESULTING IN A NORTH-SOUTH ORIENTED RIDGE AXIS EXTENDING FROM KOREA TO EAST OF THE PHILIPPINES. TD 05W WILL TRACK NORTH-NORTHEASTWARD ALONG THE WEST SIDE OF THIS RIDGE COMPLEX THROUGH TAU 96. AROUND THE TIME THE SYSTEM MAKES LANDFALL ALONG THE EAST COAST OF MAINLAND CHINA (NEAR TAU 96), THE PRIMARY STEERING INFLUENCE SHIFTS ONCE MORE TO THE STR OVER KOREA AND THE SYSTEM WILL PUSH INLAND OVER EASTERN CHINA THROUGH TAU 120. TD 05W IS FORECAST TO INTENSIFY AT ROUGHLY THE CLIMATOLOGICAL RATE FOR THE FIRST 24 HOURS, AS THE VORTEX BECOMES VERTICALLY ALIGNED. THE PACE OF INTENSIFICATION INCREASES FROM TAU 24 AS THE TUTT STRENGTHENS TO THE NORTHEAST OF TAIWAN, ENHANCING THE POLEWARD OUTFLOW CHANNEL. WHILE THE FORECAST CALLS FOR A PEAK OF 75 KNOTS AT TAU 48, THE ACTUAL PEAK IS LIKELY TO OCCUR AROUND TAU 60, AND COULD BE 10-15 KNOTS HIGHER, AS THE SYSTEM MOVES INTO THE SOUTHERN ENTRANCE TO THE TAIWAN STRAIT. WHILE PASSING THROUGH THE STRAIT, EASTERLY DOWNSLOPE WINDS OFF TAIWAN WILL DISRUPT THE VORTEX, LEADING TO A GENERAL WEAKENING TREND PASS THROUGH THE TAIWAN STRAIT. BY THE TIME IT LEAVES THE STRAIT, THE SYSTEM WILL HAVE WEAKENED BELOW TYPHOON STRENGTH AS IT EXPERIENCES INCREASED SHEAR AND DECREASED OUTFLOW ALOFT. AFTER LANDFALL, THE SYSTEM WILL RAPID WEAKEN WHILE MOVING FURTHER INLAND. MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS SPLIT, WITH ROUGHLY HALF OF THE GUIDANCE SUPPORTING A WEST OF TAIWAN TRACK AND HALF SUPPORTING AN EAST OF TAIWAN SCENARIO. ECMWF, ECEPS, EC-AIFS, GALWEM AND THE CONSENSUS MEAN ALL SUPPORT THE JTWC TRACK UP THE WEST SIDE OF TAIWAN AND THROUGH THE TAIWAN STRAIT. THE GFS AND GEFS MEANWHILE CLIP THE SOUTHERN TIP OF TAIWAN AND TRACK INTO THE SOUTHERN EAST CHINA SEA TO THE WEST OF OKINAWA. ENSEMBLE SPREAD IS SIGNIFICANT, THOUGH ALL MEMBERS OF THE GEFS TRACK EAST OF TAIWAN AND ALL BUT FIVE MEMBERS OF THE ECEPS TRACK WEST OF TAIWAN, WITH SOME STRONG MEMBERS PUSHING INLAND EAST OF HONG KONG. THE JTWC FORECAST IS POSITIONED CLOSE TO THE EC-AIFS TRACK THROUGH THE FORECAST PERIOD WITH LOW CONFIDENCE. INTENSITY GUIDANCE IS SOMEWHAT SURPRISINGLY IN GOOD AGREEMENT, AS THE MAJORITY OF THE MESOSCALE GUIDANCE FAVORS THE WEST OF TAIWAN TRACK. THE HWRF TAKES THE SYSTEM OVER TAIWAN AND THUS SHOWS RAPID WEAKENING AFTER TAU 48, BUT THE REMAINDER OF THE GUIDANCE ALL SHOW A PEAK OCCURRING AT TAU 48, WITH A RANGE BETWEEN 60 AND 95 KNOTS. THE HIGHER-END MODELS INCLUDE THE RIDE AND RICN RAPID INTENSIFICATION (RI) MODELS, BOTH OF WHICH ARE TRIPPED. THE JTWC FORECAST IS POSITIONED ON TOP OF THE CONSENSUS THROUGH TAU 24 THEN INCREASES AT A FASTER RATE THROUGH THE PEAK. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN