WDPN31 PGTW 200900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING NR 028// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 02W (SURIGAE), LOCATED APPROXIMATELY 300 NM EAST- NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT 05 KTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT TY SURIGAE CONTINUES TO MAINTAIN A ROUGHLY 30-NM WIDE EYE, THOUGH AT LEAST IN THE VISIBLE AND INFRARED BANDS HAS BECOME SLIGHTLY MORE RAGGED. A 200502Z AMSR2 MICROWAVE PASS CONFIRMED A VERY WELL DEFINED AND INTENSE 30-NM EYEWALL AND THE 37GHZ IMAGE REVEALED A SMALLER AND WEAKER INNER EYEWALL AT ABOUT 15-NM FROM THE CENTER. THE INITIAL INTENSITY REMAINS STEADY AT 115 KTS, SUPPORTED BY MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T6.5 FROM PGTW, AND T6.0 FROM RJTD AND KNES, AN ADT ESTIMATE OF T6.1 AND A SATCON ESTIMATE OF 121 KTS AND IS HEDGED SLIGHTLY LOWER IN LIGHT OF A 200502Z AMSR2 WINDSPEED MEASUREMENT OF 110 KTS. TY 02W REMAINS IN A GENERALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW (8-12 KTS) AND STRONG POLEWARD AND EQUATORWARD OUTFLOW. SSTS REMAIN GENERALLY WARM, THOUGH RECENT HYCOM MODEL ANALYSIS SUGGESTS SIGNIFICANT UPWELLING, PRIMARILY TO THE SOUTH IN THE STORMS WAKE. HOWEVER, NOW THAT THE SYSTEM HAS PICKED UP FORWARD SPEED ONCE MORE, IT IS MOVING AWAY FROM THE INDUCED POOL OF COOLER WATERS AND INTO A REGION OF 27-28C WATERS. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY SURIGAE IS FORECAST TO TRACK NORTHEASTWARD ALONG THE WESTERN PERIPHERY OF A DEEP SUBTROPICAL RIDGE (STR) THROUGH TAU 36, THEN ROUND THE RIDGE AXIS AND TURN SHARPLY NORTHEAST AHEAD OF STRONG MID-LATITUDE SHORTWAVE TROUGH MOVING IN FROM THE WEST. BY TAU 72, SURIGAE WILL BE ON A NEAR EASTWARD COURSE, STEADILY ACCELERATING AS IT BEGINS TO INTERACT WITH THE SUBTROPICAL JET ALOFT. THERE IS NO SIGNIFICANT CHANGE EXPECTED IN THE UPPER-LEVEL ENVIRONMENT, WITH LOW VWS AND STRONG POLEWARD OUTFLOW PERSISTING THROUGH TAU 36. THE PRIMARY INTENSITY FACTORS ARE THUS THE RELATIVELY MARGINAL SSTS (27C) AND THE LARGE SIZE OF THE CORE AND THE TWO FACTORS TOGETHER SUPPORT A STEADY OR GRADUAL DECREASE IN INTENSITY THOUGH TAU 12 AND THEN STEADIER WEAKENING THROUGH TAU 36. ONCE THE SYSTEM MAKES THE TURN NORTHEAST BY TAU 48, STEADY WEAKENING IS FORECAST AS THE SYSTEM ENCOUNTERS STEADILY COOLER SSTS, AT OR BELOW 26C, AND DRAMATICALLY INCREASED MID-LEVEL SHEAR. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 AND THE JTWC FORECAST TRACK IS SET WITH HIGH CONFIDENCE. THE INTENSITY FORECAST IS SET ON THE HIGH END OF THE GUIDANCE ENVELOPE AND CLOSELY TRACKS THE HWRF SOLUTION WITH MODERATE CONFIDENCE. C. IN THE LATER PORTION OF THE FORECAST, TY SURIGAE WILL CONTINUE TO ACCELERATE EAST-NORTHEASTWARD AHEAD OF AN ADVANCING MAJOR SHORTWAVE TROUGH AND ALONG THE NORTHERN PERIPHERY OF THE STR TO THE SOUTHEAST. MOST AVAILABLE GUIDANCE SUGGESTS THAT TC 02W WILL NOT BE CAPTURED BY THE PASSING SHORTWAVE, WHICH WILL MISS THE SYSTEM TO THE NORTH, BUT WILL CONTINUE TRACKING EASTWARD AS IT WEAKENS. THE PRIMARY IMPACT OF THE SHORTWAVE WILL BE TO IMPART A STRONG WESTERLY FLOW ALOFT, INCREASING VWS TO ABOVE 50 KTS. THE SYSTEM WILL TRANSIT GENERALLY ALONG THE 26C ISOTHERM, BUT DUE TO THE VERY HIGH SHEAR AND THE CONVERGENT NATURE OF THE WESTERLY FLOW ALOFT, WILL STEADILY WEAKEN THROUGH TAU 120. AS TY 02W MOVES EASTWARD ALONG THE BAROCLINIC ZONE AND DEVELOPS A FRONTAL STRUCTURE, IT IS FORECAST TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 96. NUMERICAL MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT THOUGH BEGINS TO SHOW SIGNIFICANT SPREAD IN BOTH ALONG AND CROSS-TRACK UNCERTAINTY AFTER TAU 96 DUE TO THE UNCERTAINTY SURROUNDING THE IMPACT OF THE SHORTWAVE TROUGH. THE JTWC FORECAST TRACK IS SET JUST SOUTH FROM THE PREVIOUS FORECAST AND LIES JUST NORTH OF THE MULTI-MODEL CONSENSUS WITH MODERATE CONFIDENCE.// NNNN