WDPN31 PGTW 231500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (SURIGAE) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.5N 137.6E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 413 NM NORTH-NORTHWEST OF ULITHI MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL DEPRESSION (TD) 25W (SURIGAE) AS A COMPLETELY OBSCURED LOW-LEVEL CIRCULATION CENTER WITH PERIPHERY LOW-LEVEL CLOUD BANDING VISIBLE FROM UNDER THE EXPANDING CANOPY. THE 231101Z PARTIAL ASCAT PASS REVEALS THE EASTERN SEMICIRCLE AND AN ASYMMETRIC WIND FIELD. THE HIGHEST 30 KT WIND SPEEDS ARE A RESPECTABLY SIZED SWATH CONFINED TO THE NORTHEASTERN QUADRANT, WHILE THE SOUTHEASTERN QUADRANT IS RELEGATED TO A SMALL STRIP OF 15-20 KT WINDS. ENVIRONMENTAL ANALYSIS REVEALS A HIGHLY FAVORABLE ENVIRONMENT, CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), VERY WARM (29-30 C) SEA SURFACE TEMPERATURES (SST), HIGH (100-120 KJ PER CM SQUARED) OCEAN HEAT CONTENT (OHC), STRONG POLEWARD OUTFLOW, AND AMPLE MOISTURE THROUGHOUT THE AIR COLUMN. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTIAL ASCAT PASS FROM 231101Z. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE CIMSS AUTOMATED INTENSITY ESTIMATES AND THE AGENCY DVORAK FIXES LISTED BELOW. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: A DEEP-LAYER SUBTROPICAL RIDGE CENTERED TO THE NORTH-NORTHEAST OF THE SYSTEM AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.0 - 30 KTS CIMSS ADT: 28 KTS AT 231140Z CIMSS AIDT: 30 KTS AT 231140Z CIMSS D-MINT: 30 KTS AT 230945Z CIMSS D-PRINT: 30 KTS AT 231140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 25W (SURIGAE) IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD WHILE IT REMAINS UNDER THE STEERING INFLUENCE OF THE DEEP-LAYER STR CURRENTLY CENTERED TO ITS NORTH-NORTHEAST. 25W IS EXPECTED TO MAINTAIN A RELATIVELY CONSISTENT TRACK SPEED THROUGH TAU 48-60, AT WHICH POINT, THE STORM IS FORECAST TO SLOW SLIGHTLY AS IT APPROACHES A WEAKNESS BETWEEN THE STEERING RIDGE AND A WEAKER MID- LAYER STR CURRENTLY CENTERED OVER CHINA. AROUND TAU 60-72, SURIGAE WILL CONTINUE TO SLOW ITS SPEED OF ADVANCE AND TURN NORTH- NORTHWESTWARD INTO THE WEAKNESS AND BEGIN TO TRACK AROUND THE SOUTHWESTERN PERIPHERY OF THE STEERING RIDGE TOWARDS THE RIDGE AXIS. BETWEEN TAU 72-96, 25W IS FORECAST TO RECURVE ABOUT THE STEERING RIDGE WHILE TRACKING CONSIDERABLY SLOWER. FROM TAU 96 THROUGH THE END OF THE FORECAST PERIOD, 25W WILL BEGIN TO ACCELERATE TO THE NORTH-NORTHEAST WHILE THE DEEP-LAYER STR MAINTAINS STEERING AUTHORITY OVER THE SYSTEM. REGARDING INTENSITY, 25W IS FORECAST TO STEADILY INTENSIFY WHILE IT CONTINUES TO CONSOLIDATE THROUGH TAU 48. AT THAT POINT, 25W MAY UNDERGO A PERIOD OF RAPID INTENSIFICATION. THE ENVIRONMENT IS EXPECTED TO BE HIGHLY FAVORABLE THROUGH THE ENTIRE FORECAST PERIOD, ESPECIALLY BETWEEN TAU 48-96. DURING THAT TIME, SURIGAE IS EXPECTED TO DEVELOP A ROBUST POLEWARD OUTFLOW CHANNEL, IN ADDITION TO DECREASING VWS AND SLOWER TRACK SPEEDS OVER HIGH OHC VALUES. 25W IS CURRENTLY FORECAST TO PEAK AT TAU 120, WITH ADDITIONAL INTENSIFICATION POSSIBLE OUTSIDE THE FORECAST PERIOD. MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE CONTINUES TO DEPICT A BIFURCATION SCENARIO BEGINNING AROUND TAU 72 AS 25W ENCOUNTERS THE WEAKNESS BETWEEN THE TWO SUBTROPICAL RIDGES. THE BIFURCATION IS SPLIT GENERALLY BETWEEN THE PHYSICS-BASED MODELS AND EXPERIMENTAL AI-BASED MODELS. SOME GLOBAL PHYSICS-BASED MODELS INDICATE 25W COULD FAIL TO RECURVE AND INSTEAD TRANSITION STEERING INFLUENCES TO THE WEAKER STR OVER CHINA AND TRACK NORTHWESTWARD INTO TAIWAN; HOWEVER, GFS, ECMWF, AND NAVGEM NOW LIE AMONGST THE AI MODELS THAT DEPICT A RECURVE SCENARIO. ALL EXPERIMENTAL AI-BASED MODELS SUPPORT THE RECURVE SCENARIO. DUE TO THE CHARACTERIZATION OF THE ENVIRONMENTAL SETUP IN GLOBAL MODELS AND THE INCREASED MODEL AGREEMENT BETWEEN AI-BASED MODELS AND THE MOST RELIABLE PHYSICS-BASED MODELS, THE RECURVE SCENARIO REMAINS THE MOST LIKELY OUTCOME. THE TRACK FORECAST CONFIDENCE IS PLACED WITH MEDIUM CONFIDENCE FROM TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-120 DUE TO THE REMAINING UNCERTAINTY SURROUNDING THE RECURVE SCENARIO. RELIABLE INTENSITY GUIDANCE IS IN STRONG AGREEMENT IN A STEADY RATE OF INTENSIFICATION THROUGH TAU 48 WHILE 25W CONTINUES TO CONSOLIDATE, FOLLOWED BY AN INCREASED RATE OF INTENSIFICATION BETWEEN TAU 48-96. THE GUIDANCE DIVERGES WITH RESPECT TO PEAK INTENSITY, RANGING ANYWHERE FROM 80 KTS (GFS) TO 130-135 KTS (COAMPS-TC AND HAFS-A) AT TAU 120. THE JTWC INTENSITY FORECAST LIES VERY CLOSE TO THE HAFS-A SOLUTION AND THE MULTI-MODEL CONSENSUS FROM TAU 0-48, AND HEDGED SLIGHTLY HIGHER THAN THE CONSENSUS TOWARDS THE MESOSCALE MODELS FROM TAU 48-120. AS A RESULT, THE JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE FROM TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-120. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN