WDPN31 PGTW 271500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (DOLPHIN) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.6N 175.2E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 601 NM EAST-SOUTHEAST OF WAKE ISLAND MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 19 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A COMPACT SYSTEM, WITH WELL-DEFINED SPIRAL RAINBANDS WRAPPING INTO A QUICKLY CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC). A LACK OF RECENT MICROWAVE IMAGERY AND SCATTEROMETER PASSES PRECLUDES A DEFINITIVE ANALYSIS OF THE INNER-CORE STRUCTURE. HOWEVER, THE VORTICAL HOT TOWERS (VHTS) SEEN IN THE EIR ARE STRUGGLING TO CONSOLIDATE AND WRAP INTO THE EASTERN SEMICIRCLE OF THE CIRCULATION, INDICATIVE OF LOW TO MODERATE EASTERLY VERTICAL WIND SHEAR (VWS) SLIGHTLY ELEVATED ABOVE CIMSS ANALYZED VALUES. ENVIRONMENTAL FLOW IS CHARACTERIZED BY DEEP EASTERLIES BASED ON THE LATEST CIRA DERIVED MOTION VECTOR (DMV) ANALYSIS, WHICH SUPPORTS THE PRESENCE OF LOW-TO- MODERATE EASTERLY SHEAR IMPACTING THE SYSTEM. THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE, PLACED NEAR THE CENTROID OF RECENT DVORAK POSITION FIXES. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BIASED TOWARDS THE HIGHER T3.0 FIX FROM PHFO AND THE CONGRUENT D-PRINT ESTIMATE. THE ENVIRONMENT IS OPTIMAL FOR RAPID INTENSIFICATION (RI) TO EXTREME RAPID INTENSIFICATION (ERI), WITH MINIMAL DEEP-LAYER SHEAR, STRONG POLEWARD AND EQUATORWARD OUTFLOW ALOFT, VERY WARM SSTS (29-30C) AND HIGH OCEAN HEAT CONTENT (OHC). INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK. CURRENT STEERING MECHANISM: SOUTHERN FLANK OF AN EXPANSIVE SUBTROPICAL RIDGE (STR) COMPLEX TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS PHFO: T3.0 - 45 KTS CIMSS ADT: 41 KTS AT 271140Z CIMSS AIDT: 36 KTS AT 271140Z CIMSS D-PRINT: 47 KTS AT 271140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 0-5 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG POLEWARD AND EQUATORWARD OTHER FACTORS: HIGH OCEAN HEAT CONTENT (OHC). ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM (TS) 12W (DOLPHIN) HAS BEGUN TO GRADUALLY TURN ONTO A MORE WESTWARD TRAJECTORY OVER THE PAST SIX HOURS, UNDER THE STEERING INFLUENCE OF THE SOUTHEASTERN FLANK OF A LARGE STR TO THE NORTHWEST. OVER THE NEXT 24 TO 36 HOURS, AN EXPANSIVE, DEEP-LAYER UPPER-LEVEL CYCLONE WILL MOVE SOUTHWESTWARD AND TAKE UP POSITION NEAR 30N 175E, INDUCING A WEAKNESS IN THE STR PATTERN AND RESULTING IN A WEAKENING STEERING GRADIENT. IN RESPONSE, TS 12W WILL DECELERATE WHILE MAINTAINING A GENERAL WESTWARD TRACK. BY TAU 36, A SECOND STR AXIS CENTERED WEST OF HAWAII WILL BUILD WESTWARD, EVENTUALLY CUTTING OFF THE LARGE UPPER-LEVEL LOW AND CONNECTING WITH THE STR CENTER EAST OF JAPAN. THIS WILL PRESENT A NORTHWEST-SOUTHEAST ORIENTED STEERING RIDGE TO THE NORTHEAST OF TS 12W. SIMULTANEOUSLY, A DEEP MID-LATITUDE TROUGH, REACHING ALL THE WAY DOWN TO 30N, WILL TRACK EAST OF JAPAN. THE COMBINATION OF THESE FACTORS WILL INDUCE TS 12W TO TURN ONTO A NORTHWESTWARD TRACK AFTER TAU 36, CONTINUING THROUGH THE END OF THE FORECAST PERIOD. REGARDING INTENSITY, AS MENTIONED ABOVE, THE ENVIRONMENT IS OPTIMAL TO SUPPORT RI OR ERI. THE VORTEX MUST FULLY CONSOLIDATE AND SYMMETRIZE FIRST, WHICH IS EXPECTED IMMINENTLY. ONCE VORTEX ALIGNMENT IS ACHIEVED, THE SYSTEM WILL COMMENCE A PERIOD OF ERI, EXPECTED TO REACH SUPER TYPHOON STRENGTH (130 KTS) BY TAU 60 AND A PEAK INTENSITY OF 140 KTS OR HIGHER BY TAU 72. BEYOND TAU 72, THE INTENSITY FORECAST IS HIGHLY UNCERTAIN. BOTH THE HWRF AND HAFS-A EXPLICITLY PREDICT AN EYEWALL REPLACEMENT CYCLE (ERC) BEGINNING IMMEDIATELY AFTER TAU 72, RESULTING IN BOTH A TEMPORARY WEAKENING OF THE SYSTEM AND AN EXPANSION OF THE OUTER WIND FIELD. HOWEVER, THE EXACT TIMING OF POSSIBLE ERCS AND THEIR STRUCTURAL IMPACTS ARE TOO FAR IN THE FUTURE TO RELIABLY PREDICT AT THIS POINT, AND SIGNIFICANT INTENSITY FLUCTUATIONS ARE POSSIBLE. MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72. CROSS-TRACK SPREAD IS MINIMAL (70NM) UP TO TAU 72, WITH JGSM AND GALWEM MARKING THE SOUTHERN EDGE OF THE ENVELOPE, WHILE THE ECENS AND GEFS ENSEMBLE MEANS ARE POSITIONED ON THE NORTHERN EDGE. THE JTWC FORECAST IS PLACED ALONG THE NORTHERN SIDE OF THE INNER GROUPING OF MODEL TRACKERS, CONSISTENT WITH THE EXPERIMENTAL AI (FNV3) AND ECMWF GUIDANCE, WITH HIGH CONFIDENCE. BEYOND TAU 72, THE GUIDANCE ENVELOPE GRADUALLY EXPANDS TO 230NM, PRIMARILY DRIVEN BY A DEPARTURE OF THE JGSM TRACKER TO A MORE WEST-NORTHWESTWARD TRACK. ENSEMBLE GUIDANCE CONTINUES TO SUPPORT A HIGH CONFIDENCE TRACK FORECAST THROUGH TAU 72, WITH INCREASING UNCERTAINTY IN THE EXTENDED RANGE FORECAST. BY TAU 120, THE EXPERIMENTAL JTWC SUPER-ENSEMBLE SHOWS A VERY LARGE SPREAD IN INDIVIDUAL ENSEMBLE MEMBERS, EXTENDING ACROSS A WIDE SWATH OF THE WESTERN PACIFIC. THE EXTENDED RANGE JTWC FORECAST IS PLACED NEAR THE AI CONSENSUS TRACKER AND THE MULTI-MODEL CONSENSUS MEAN, ON THE NORTHERN SIDE OF THE ENVELOPE, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE REMAINS IN GOOD AGREEMENT, WITH THE NOTABLE EXCEPTION OF THE NAVGEM-DERIVED COAMPS-TC AND BOTH DECAY SHIPS OUTPUTS, WHICH ARE SKEWED UNREALISTICALLY LOW DUE TO A LOSS OF ACCURATE SST INPUTS. THE REMAINDER OF THE MESOSCALE MODELS ALL DEPICT STEADY TO RAPID INTENSIFICATION TO A PEAK OF 130-150 KTS. THE JTWC FORECAST IS CONSISTENT WITH THE EXPERIMENTAL AI MODEL GUIDANCE, THE RIDE AND CTR1 RI AIDS, AND IS SLIGHTLY HIGHER THAN THE HWRF MODEL. CONFIDENCE IS LOW IN THE EXTENDED RANGE DUE TO UNCERTAINTY SURROUNDING THE TIMING, DURATION, AND MAGNITUDE OF POTENTIAL ERCS. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN