WDPN31 PGTW 200300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING NR 027// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 02W (SURIGAE), LOCATED APPROXIMATELY 350 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWARD AT 03 KTS OVER THE PAST SIX HOURS. SURIGAE CONTINUES TO DISPLAY A LARGE CORE, WITH A 200140Z GMI MICROWAVE PASS SHOWING AM INTENSE 65 NM DIAMETER PRIMARY EYEWALL. A WEAKER INNER EYEWALL OF 30 NM DIAMETER REMAINS EVIDENT IN MICROWAVE AND ENHANCED INFRARED (EIR) IMAGERY, THOUGH IT HAS SHOWN SIGNS OF CONTINUED DEGRADATION IN RECENT HOURS AS THE CENTRAL WARM SPOT IN EIR IMAGERY EXPANDS. THE CURRENT INTENSITY IS HELD CONSTANT AT 115 KT, SUPPORTED BY DVORAK ESTIMATES OF T6.0 FROM RJTD AND T6.0/6.5 FROM PGTW. SURIGAE’S ENVIRONMENT CONTINUES TO BE GENERALLY FAVORABLE, WITH EXPANSIVE CIRRUS OUTFLOW REFLECTING THE LOW VERTICAL WIND SHEAR (VWS) OF UNDER 10 KTS. BACKGROUND SEA SURFACE TEMPERATURE (SST) REMAINS WARM, AROUND 28C, BUT COUPLED HWRF/HYCOM ANALYSIS INDICATES THAT THE TYPHOON’S CIRCULATION IS AT LEAST PARTIALLY OVERLAPPING A WAKE OF COOLED WATER ALONG THE STORM TRACK, INDUCED BY SURIGAE’S SLOW FORWARD MOTION. THIS IS LIKELY THE PRIMARY INHIBITOR CURRENTLY CAPPING SURIGAE’S INTENSITY. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. ABSENT ANY SIGNIFICANT ATMOSPHERIC INHIBITORS, THE PRIMARY GOVERNORS OF INTENSITY DURING THE NEXT 48 HOURS ARE VORTEX STRUCTURE AND UNDERLYING SST. THE HIGH-RESOLUTION HWRF MODEL IS CONSISTENTLY PREDICTING SURIGAE'S LARGE CORE SIZE TO PERSIST AS MODERATE OCEAN COOLING BENEATH THE TYPHOON RESISTS EYEWALL CONTRACTION. BOTH OF THESE REALITIES FAVOR STEADY OR GRADUALLY DECREASING INTENSITY FOR THE NEXT 48 HOURS UNTIL SURIGAE RECURVES NORTHEASTWARD, ENCOUNTERING COOLER SST AND HIGHER VWS, AT WHICH POINT STEADY WEAKENING IS EXPECTED. THE INTENSITY FORECAST IS IN BEST AGREEMENT WITH HWRF ON THE HIGH SIDE OF THE MODEL CONSENSUS, PRIMARILY DUE TO THE CONTINUING PERSISTENCE OF SURIGAE’S INTENSITY, DEFYING THE MORE RAPID WEAKENING PREDICTED BY OTHER MODELS. COAMPS-TC IS 15-20 KTS WEAKER THROUGH 48 HOURS, BUT SEEMINGLY DUE TO UNREALISTICALLY EXTREME OCEAN COOLING IN THAT MODEL. THE TRACK FORECAST IS ESSENTIALLY UNCHANGED FROM THE PREVIOUS ONE THROUGH 72 HOURS, WITH A NORTHEASTWARD TURN EXPECTED IN ABOUT 48 HOURS, FOLLOWING THE PERIPHERY OF AN UPPER-LEVEL RIDGE TO THE EAST OF THE TYPHOON AS A MID-LATITUDE SHORTWAVE TROUGH APPROACHES FROM EASTERN CHINA. THIS WILL INDUCE ACCELERATION IN FORWARD SPEED AS SURIGAE BEGINS INTERACTING WITH THE SUBTROPICAL JET (STJ). CONFIDENCE IN THIS PORTION OF THE FORECAST TRACK REMAINS HIGH. C. DURING THE 96-120 HOUR PERIOD, SURIGAE IS EXPECTED TO ACCELERATE EAST-NORTHEASTWARD AS A SHORTWAVE TROUGH CROSSES THE RYUKYU ISLANDS AND IMPARTS STRONG WESTERLY FLOW ON THE CYCLONE. MOST MODELS CURRENTLY ANTICIPATE THAT THE TYPHOON WILL NOT PHASE FAVORABLY WITH THIS SHORTWAVE, AND WILL LAG BEHIND AS THE SHORTWAVE CONTINUES EASTWARD. THUS, HIGH VWS AND COOLING SST ARE EXPECTED TO CAUSE STEADY WEAKENING THROUGH 120 HOURS TO BELOW TYPHOON INTENSITY. SURIGAE WILL BE INTERACTING WITH A PRONOUNCED LOW-LEVEL THERMAL GRADIENT DURING THIS TIME, WHICH IS EXPECTED TO INDUCE THE ONSET OF EXTRATROPICAL TRANSITION AS THE CYCLONE ACQUIRES FRONTAL STRUCTURE. THIS COMPLEX EVOLUTION INTRODUCES UNCERTAINTY IN EXACTLY HOW QUICKLY THE CYCLONE WILL WEAKEN, AS WELL AS HOW SWIFTLY IT WILL MOVE EASTWARD. THE TRACK FORECAST HAS BEEN NUDGED SLIGHTLY SOUTHWARD FROM THE PREVIOUS ONE AT 96-120 HOURS ALONG WITH THE MULTI-MODEL CONSENSUS TREND, AND IS OF MODERATE CONFIDENCE.// NNNN