WDPN31 PGTW 022100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 028// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 24.0N 149.4E INITIAL INTENSITY: 105 KTS GEOGRAPHIC REFERENCE: 445 NM EAST OF IWO TO MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 52 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CIRCULAR, 30 NM WIDE EYE EMBEDDED WITHIN A SYMMETRIC CENTRAL DENSE OVERCAST (CDO) AND EXTENSIVE SPIRAL BANDS ALONG THE PERIPHERY. THE OVERALL EXTENT OF THE COLDEST CLOUD TOPS HAS DECREASED AS THE CDO ITSELF SHRINKS, THOUGH THE CONVECTION ALONG THE EYEWALL REMAINS ENERGETIC. THIS CONVECTION IS SUPPORTED BY GOOD RADIAL OUTFLOW ALOFT, INDICATING A LOW-SHEAR ENVIRONMENT. MULTIPLE RECENT PASSES BY MICROWAVE SOUNDERS BETWEEN 021040Z AND 021543Z AND THE 021613Z AMSR2 IMAGER CONFIRMS THAT AN OUTER, FRAGMENTED CONVECTIVE RING IS ATTEMPTING TO CONSOLIDATE AROUND THE EYEWALL, FORESHADOWING THE ONSET OF A FOURTH EYEWALL REPLACEMENT CYCLE (ERC). WHILE TYPHOON (TY) 12W IS TRAVERSING OVER VERY WARM SEA SURFACE TEMPERATURES (SST) OF 30-31 DEGREES CELSIUS, THE UNDERLYING SUB-SURFACE TEMPERATURES ARE COOLER, RESULTING IN A LOWER OCEAN HEAT CONTENT (OHC). THIS CONDITION INCREASES THE LIKELIHOOD OF FASTER UPWELLING OF COOLER WATER, WHICH HAS LARGELY BEEN RESPONSIBLE FOR THE DEGRADATION IN STRUCTURE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED, CLOUD-FREE EYE. AS THE CONVECTIVE STRUCTURE CONTINUES TO DEGRADE, THE INITIAL INTENSITY HAS BEEN LOWERED TO 105 KTS WITH MEDIUM CONFIDENCE, WHICH IS SUPPORTED BY THE T5.0-6.0 FIXES AND THE DECREASING OBJECTIVE ESTIMATES FROM CIMSS RANGING FROM 92 KTS TO 119 KTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: THE SOUTHWESTWARD EXTENSION OF THE DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.5 - 102 KTS RJTD: T6.0 - 115 KTS RCTP: T5.0 - 90 KTS KNES: T5.5 - 102 KTS CIMSS SATCON: 110 KTS AT 021500Z CIMSS ADT: 92 KTS AT 021800Z CIMSS AIDT: 95 KTS AT 021800Z CIMSS D-MINT: 112 KTS AT 021614Z CIMSS D-PRINT: 86 KTS AT 021800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 30-31 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY 12W IS BEING STEERED WEST-NORTHWESTWARD BY THE WESTERN EXTENSION OF A STR CENTERED NEAR 43N 175W. THIS PATTERN WILL HOLD THROUGH TAU 48, GUIDING THE CENTER TOWARD A VERY CLOSE PASSAGE TO IWO TO. AFTER TAU 48, THE PRIMARY STEERING INFLUENCE WILL TRANSITION TO A SEPARATE STR CENTERED OVER THE KOREAN PENINSULA, WHICH WILL MAINTAIN THE ESTABLISHED DIRECTION OF MOTION. AS THE TYPHOON APPROACHES THE RYUKYU ISLANDS, ITS FORWARD MOTION WILL DECREASE FROM 12-13 KTS AT TAU 48 TO 08 KTS AT TAU 120. THIS DECELERATION WILL BE CAUSED BY A LARGE CYCLONE PASSING OVER EASTERN SIBERIA, WHICH WILL FLATTEN THE STEERING RIDGE AND RESULT IN A WEAKER STEERING GRADIENT. TY 12W IS NOW ON A GRADUAL WEAKENING TREND THAT WILL PERSIST THROUGHOUT ITS JOURNEY WESTWARD. WHILE SOME ENVIRONMENTAL FACTORS FOR TY 12W WILL BE FAVORABLE, SPECIFICALLY VERY WARM SST AND LOW VERTICAL WIND SHEAR, THE ERC AND LOWER OHC WILL BE THE MAIN LIMITING FACTORS, LEADING TO SLOW DEGRADATION OF THE CONVECTIVE STRUCTURE. THE ERC WILL DEGRADE THE INNER CORE AS THE OUTER RING CONSOLIDATES, AND THE LOWER OHC WILL BE INCAPABLE OF SUPPORTING A STORM OF HIGH INTENSITY. IT IS WORTH NOTING THAT, BECAUSE OF THE LARGE INNER CORE, THE ERC WILL BE SLOW AND MORE SUSCEPTIBLE TO INTERRUPTIONS FROM ENVIRONMENTAL EFFECTS. SHOULD THE ERC BEGIN IN EARNEST, IT FACES A HIGHER LIKELIHOOD OF BECOMING A PARTIAL OR STALLED EVENT AND LIKELY WILL NOT COMPLETE PRIOR TO TAU 60. CONSEQUENTLY, A PROLONGED WEAKENING TREND IS PREDICTED OUT TO TAU 96. THE ERC WILL LEAD TO STRUCTURAL CHANGES THAT WILL EXPAND THE WIND FIELD EVEN FURTHER, CAUSING HAZARDS TO EXTEND FAR FROM THE STORM CENTER. MODEL DISCUSSION: THE TRACK GUIDANCE IS VERY TIGHTLY PACKED THROUGH TAU 120, WITH THE AI MODEL CONSENSUS POSITIONED NEAR THE GLOBAL AND MESOSCALE PHYSICS-BASED MODELS. HAFS-A AND HWRF ANCHOR THE POLEWARD SIDE OF THE UNCERTAINTY ENVELOPE, WHILE NAVGEM AND JGSM BOUND THE EQUATORWARD EDGE. THE JTWC FORECAST TRACK IS VERY SIMILAR TO THE PREVIOUS, ALIGNED NEAR THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. A PRIMARY FORECAST CHALLENGE RELATES TO THE TRANSLATION SPEED OF TY 12W IN THE EXTENDED PERIOD. THE ALONG-TRACK SPREAD INCREASES FROM 125 NM AT TAU 72 TO 280 NM BY TAU 120. THIS SPREAD IS ATTRIBUTED TO DIFFERING MODEL SOLUTIONS CORRESPONDING TO THE EVOLUTION OF THE STR OVER THE KOREAN PENINSULA. FASTER MODELS LIKE ECMWF SHOW A STRONGER, MORE PERSISTENT RIDGE, WHILE THE SLOWER SOLUTIONS LIKE GFS DEPICT A MORE SIGNIFICANT FLATTENING OF THE RIDGE. THE CONSENSUS POINTS AT TAU 96 AND TAU 120 LIE NEARLY HALFWAY BETWEEN THESE TWO SCENARIOS. THE SPREAD IS ALSO QUITE LARGE AMONG THE INTENSITY AIDS. COAMPS-TC REMAINS THE LONE OUTLIER IN DEPICTING SIGNIFICANT INTENSIFICATION TO 140 KTS. THIS SOLUTION WAS DISCOUNTED. EVERY OTHER RELIABLE INTENSITY AID SHOWS SLOW TO STEADY WEAKENING THROUGH TAU 96. THE JTWC INTENSITY FORECAST ALIGNS WITH THIS WEAKENING SCENARIO WITH MEDIUM CONFIDENCE FOR THE FIRST 72 HOURS. A NOTABLE DEVELOPMENT HAS EMERGED AT TAU 120. HAFS-A PREDICTS RAPID INTENSIFICATION OF TY 12W BEGINNING AT TAU 96, BRINGING THE SYSTEM BACK OVER 100 KTS BY TAU 120 AS THE SYSTEM GRAZES OKINAWA. THIS SUGGESTS A POTENTIAL FOR THE ERC TO FINISH AND THE INNER CORE TO TIGHTEN UP. FOR NOW, THE JTWC ALIGNS WITH THE STEADY-STATE TRENDS OF THE EXPERIMENTAL GOOGLE DEEPMIND, HWRF, AND GFS SOLUTIONS. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN