WDPN31 PGTW 272100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (DOLPHIN) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.2N 173.7E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 549 NM SOUTHEAST OF WAKE ISLAND MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CONSOLIDATING TROPICAL STORM (TS), CHARACTERIZED BY SPIRAL BANDS WRAPPING INTO A RAGGED CENTRAL DENSE OVERCAST (CDO). VORTICAL HOT TOWERS, FEATURING CLOUD TOP TEMPERATURES AS COLD AS -86 DEGREES CELSIUS, ARE OBSERVED ROTATING WITHIN THE CDO ASSOCIATED WITH THE MID-LEVEL CIRCULATION. THE SYSTEM EXHIBITS ROBUST POLEWARD AND WESTWARD OUTFLOW, WHICH IS ENHANCED BY AN UPPER-LEVEL TROUGH POSITIONED TO THE NORTHEAST. MICROWAVE PASSES FROM AMSR2 AT 271335Z AND SSMIS AT 271636Z REVEALED AN INNER CORE THAT WAS OPEN ON ITS EASTERN SIDE AND A VORTEX THAT WAS TILTED TOWARD THE NORTHWEST WITH HEIGHT. WHILE TS 12W IS PRESENTLY BEING IMPACTED BY LOW TO MODERATE SOUTHEASTERLY SHEAR IN THE 400-300 MB LAYER, THE SYSTEM IS TRAVERSING WARM SEA SURFACE TEMPERATURES (SST) OF 28-29 DEGREES WITHIN AN ATMOSPHERE OF RICH, DEEP-LAYER MOISTURE. THESE FACTORS CONSTITUTE AN ENVIRONMENT THAT IS FAVORABLE FOR INTENSIFICATION. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE. IT IS PLACED WITHIN THE CLUSTER OF AGENCY FIXES AND NEAR THE CONVERGENCE POINT OF THE HOT TOWERS BUT NUDGED TO THE SOUTHEAST TO ACCOUNT FOR THE OBSERVED VORTEX TILT. THE INITIAL INTENSITY IS SET AT 45 KTS WITH MEDIUM CONFIDENCE BASED ON THE MAJORITY OF THE T3.0 SUBJECTIVE DVORAK FIXES AND A BLEND OF THE OBJECTIVE INTENSITY ESTIMATES FROM CIMSS RANGING FROM 37 KTS TO 54 KTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHERN FLANK OF AN EXPANSIVE SUBTROPICAL RIDGE (STR) TO THE NORTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T3.0 - 45 KTS RCTP: T3.0 - 45 KTS KNES: T3.0 - 45 KTS PHFO: T3.5 - 55 KTS CIMSS SATCON: 39 KTS AT 271640Z CIMSS ADT: 41 KTS AT 271800Z CIMSS AIDT: 37 KTS AT 271800Z CIMSS D-MINT: 40 KTS AT 271636Z CIMSS D-PRINT: 54 KTS AT 271800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-20 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD AND WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 12W IS CURRENTLY BEING STEERED ON A WESTWARD TRAJECTORY BY A STR CENTERED NEAR 30N 160E. AFTER TAU 24, THE RIDGE WILL BUILD TOWARDS THE NORTHEAST IN RESPONSE TO A SHARPENING TROUGH EJECTING FROM THE EASTERN COAST OF HONSHU. CONSEQUENTLY, THE SYSTEM WILL VEER NORTHWESTWARD AND APPROACH A WEAKNESS IN THE STR CREATED BY THE TROUGH. THE STORM'S FORWARD MOTION WILL SLOW FROM ITS CURRENT 15 KTS TO 8-10 KTS BY TAU 24 AS THE DEEP-LAYER RIDGE RETREATS TO THE NORTHEAST, RESULTING IN A WEAKER STEERING GRADIENT. THE ENVIRONMENT IS BECOMING EXCEPTIONALLY FAVORABLE FOR VERY SIGNIFICANT INTENSIFICATION. THE SYSTEM WILL MOVE OVER EVEN WARMER WATERS WITH SST OF 31-32 DEGREES CELSIUS AND HIGH OCEAN HEAT CONTENT OF 100-130 KJ PER CM2. CONCURRENTLY, THE MID-LEVEL SHEAR WILL ABATE WITHIN 24 HOURS. FURTHERMORE, UNTIL TAU 48-60, THE SYSTEM WILL MOVE IN PHASE WITH A 200 MB SUBTROPICAL JET TO THE NORTHEAST, WHICH WILL ENHANCE UPPER-LEVEL DIVERGENCE. AS THE INNER CORE BECOMES WELL-DEFINED, THESE CONDITIONS WILL SUPPORT RAPID INTENSIFICATION (RI) FOR THE FIRST 12 HOURS. AFTER TAU 24, THE COMBINATION OF EASING SHEAR AND EXCEPTIONALLY WARM SST WILL FUEL A PERIOD OF NEAR-EXTREME RAPID INTENSIFICATION (ERI) UP TO AT LEAST 145 KTS. AFTER THE STORM ACHIEVES PEAK INTENSITY, THE POTENTIAL FOR EYEWALL REPLACEMENT CYCLES (ERC) WILL INCREASE, LEADING TO LESS PREDICTABLE FLUCTUATIONS. THESE ERC EVENTS WILL LEAD TO AN EXPANSION OF THE WIND FIELD IN THE EXTENDED FORECAST PERIOD. MODEL DISCUSSION: THE TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 48 WITH A CROSS-TRACK SPREAD OF 65 NM. NAVGEM WAS EXCLUDED FROM THIS ANALYSIS BECAUSE IT UNREALISTICALLY DEPICTS A SHARP TURN TOWARDS THE NORTH, WHEREAS EVERY OTHER TRACKER IS CLUSTERED TOGETHER. THE AI AND PHYSICS-BASED MODELS ARE INTERMINGLED WITHIN THIS CORE CLUSTER, WHICH RAISES CONFIDENCE IN THE OVERALL TRACK PHILOSOPHY. IN THE EXTENDED PERIOD, JGSM EMERGES AS THE EQUATORWARD OUTLIER, AND THE SPREAD EXPANDS TO 265 NM. NOTABLY, THE GUIDANCE ENVELOPE HAS BEEN SHIFTING SOUTHWARD FROM CYCLE TO CYCLE, AND THE 271800Z SOLUTIONS WERE NO EXCEPTION. THE JTWC FORECAST TRACK INITIALLY ALIGNS WITH THE MULTI-MODEL CONSENSUS. FROM TAU 48 TO TAU 120, THE FORECAST TRACK IS HEDGED SOUTH OF THE CONSENSUS TO ALIGN MORE CLOSELY WITH THE TIGHTLY GROUPED SOLUTIONS OF THE GFS, ECMWF, HAFS-A, AND EXPERIMENTAL GOOGLE DEEPMIND MODELS. THE INTENSITY AIDS DEPICT A HIGH RATE OF INTENSIFICATION COMMENCING IMMINENTLY. THE CHALLENGE BECOMES DETERMINING THE RATE OF INTENSIFICATION AND THE ULTIMATE PEAK INTENSITY. A FEW OF THE RELIABLE INTENSITY AIDS DEPICT AN EVEN MORE EXTREME RATE OF DEVELOPMENT THAN THE PREDICTED 50-KT INCREASE FROM TAU 24 TO TAU 48. THE COAMPS-TC AND THE INTERPOLATED HAFS-A SOLUTIONS POINT TO A PEAK OF 155 KTS, WHILE THE NON-INTERPOLATED HAFS-A RUNS HAVE BEEN CONSISTENTLY AT 170 KTS OR HIGHER. THEREFORE, THE JTWC INTENSITY FORECAST, WHICH ALREADY AGGRESSIVELY STRENGTHENS TS 12W AND IS SET AT THE UPPER END OF THE GUIDANCE ENVELOPE, MAY BE CONSERVATIVE. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN