MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (VONGFONG) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 01W (VONGFONG), LOCATED APPROXIMATELY 505 NM EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED HIGH RESOLUTION (1-KM) AND HIGH REFRESH RATE (2-MIN) ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS COMPACT, SYMMETRICAL AND FLARING DEEP CONVECTION OVER THE ASSESSED LOW LEVEL CIRCULATION CENTER. OVER THE PAST THREE HOURS, THE SYSTEM HAS SHOWN INDICATIONS OF A NASCENT EYE FEATURE AT TIMES BUT IT HASNT YET STUCK. HOWEVER, A 1711Z AMSR2 89 GHZ MICROWAVE IMAGE DEPICTING A CLEAR CUT MICROWAVE EYE, SO THE DEVELOPMENT OF AN EYE FEATURE IN THE INFRARED CANT BE FAR OFF. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PREVIOUSLY MENTIONED AMSR2 89 GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 50 KNOTS IS HEDGED UPWARD SLIGHTLY FROM THE PGTW CURRENT INTENSITY ESTIMATE OF T3.0 (45 KNOTS) BASED ON AN ADVANCED DVORAK TECHNIQUE (ADT) ESTIMATE OF T3.2 (49 KNOTS) AND THE OVERALL IMPROVED STRUCTURE OF THE SYSTEM. TS VONGFONG IS TRAVERSING AN ENVIRONMENT FAVORABLE FOR RAPID INTENSIFICATION WITH LOW (5-10 KTS) VWS, GOOD EQUATORWARD AND POLEWARD OUTFLOW ALOFT AND WARM (29-30C) SEA SURFACE TEMPERATURES (SSTS). THE SYSTEM IS TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) CENTERED OVER THE NORTHERN MARIANA ISLANDS THAT CONTINUES TO BUILD WESTWARD. 3. FORECAST REASONING. A. WHILE THE OVERALL TRACK PHILOSOPHY HAS NOT CHANGED, THE PREVIOUS BEST TRACK POSITION FROM 1200Z HAS BEEN ADJUSTED SIGNIFICANTLY EASTWARD (~50 NM) BASED ON A REANALYSIS OF 1216Z ASCAT-A AND 1309Z ASCAT-C DATA. THIS CHANGE HAS RESULTED IN A TRACK FORECAST THAT IS FURTHER NORTH AND EAST THAN THE PREVIOUS FORECAST AND KEEPS THE SYSTEM OVER WATER LONGER, AND SIGNIFICANTLY CHANGES THE TIMING AND LOCATION OF LANDFALL. THE UPDATED TRACK ALSO RESULTS IN A SIGNIFICANT INCREASE IN THE PEAK INTENSITY, AS THE SYSTEM REMAINS OVER WATER LONGER AND WILL BE LESS IMPACTED BY TERRAIN EFFECTS. B. OVER THE NEXT 12 HOURS TS VONGFONG WILL TRACK GENERALLY NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED STR CENTERED NORTH OF GUAM, WHICH IS CURRENTLY MOVING TOWARDS THE WEST. AFTER TAU 12, THE STR WILL RECENTER NEAR 20N 130E, AND PUSH TS VONGFONG ONTO A MORE WESTERLY TRACK THROUGH 36. THEREAFTER, THE STR REORIENTS AND MOVES A BIT FURTHER TO THE EAST, ALLOWING FOR THE SYSTEM TO BEGIN TO MOVE NORTHWESTWARD BY TAU 72. THE ENVIRONMENT WILL REMAIN HIGHLY FAVORABLE FOR RAPID INTENSIFICATION THROUGH TAU 48 WITH LOW VWS (5-10 KNOTS), HIGH SSTS (29-30 CELSIUS) AND STRONG RADIAL OUTFLOW PROVIDED BY AN UPPER-LEVEL POINT SOURCE OVER TOP OF THE SYSTEM. THE SYSTEM IS EXPECTED TO REACH PEAK INTENSITY OF 95 KNOTS BY TAU 48 AS IT APPROACHES THE SOUTHEAST TIP OF LUZON. NUMERICAL MODEL GUIDANCE ARE IN FAIR AGREEMENT THROUGH TAU 72 WITH THE MAJORITY (INCLUDING ECMWF, GFS, NAVGEM AND JGSM) ALL FAVORING A TRACK THAT REMAINS OFFSHORE OR JUST BRUSHES THE CENTRAL PHILIPPINE ISLANDS, WHILE THE UKMET AND ITS ENSEMBLE ARE THE SOLE SOLUTIONS THAT FAVOR A MORE SOUTHERLY TRACK ACROSS THE CENTRAL PHILIPPINES AND INTO THE SOUTH CHINA SEA. MODEL SPREAD AT TAU 72 IS 195NM BETWEEN OUTLIERS (EGRR AND NAVGEM). THE JTWC FORECAST TRACK THROUGH TAU 72 FAVORS THE AFOREMENTIONED CLUSTER OF MODEL SOLUTIONS WHICH LIE ON THE NORTHERN SIDE OF THE TRACK ENVELOPE WITH MODERATE CONFIDENCE. C. AFTER TAU 72 TS VONGFONG WILL MOVE FIRST NORTHWESTWARD, THEN NORTH AND FINALLY NORTHEASTWARD AS IT RECURVES AROUND THE RIDGE AXIS. TRACK SPEED WILL SLOW AS IT REACHES THE RIDGE AXIS, SIMULTANEOUS TO MOVING OVER NORTHERN LUZON, AND THEN ACCELERATE INTO THE PHILIPPINE SEA AFTER ROUNDING THE AXIS AND EMERGING OVER WATER AROUND TAU 100. A SECOND LANDFALL IS EXPECTED IN CENTRAL LUZON AROUND TAU 84. AS THE SYSTEM SKIRTS SOUTHEAST LUZON, THE INTENSITY IS FORECAST TO REMAIN STEADY AS IT TRACKS OVER COASTAL WATERS AND FEELS SOME EFFECTS OF THE TERRAIN OFFSET BY THE CONTINUED STRONG OUTFLOW, PARTICULARLY POLEWARD AS THE OUTFLOW PATTERN BEGINS TO TAP INTO THE STRONG WESTERLY FLOW TO THE NORTH. AS THE SYSTEM TRACKS OVER CENTRAL LUZON BY TAU 96 IT WILL UNDERGO SIGNIFICANT WEAKENING DUE PRIMARILY TO INTERACTION WITH THE MOUNTAINOUS TERRAIN. ONCE BACK OVER OPEN WATERS, INCREASING VWS AND COOLER WATERS WILL SERVE TO OFFSET STRONG, DIVERGENT OUTFLOW RESULTING IN IT MAINTAINING STRONG TROPICAL STORM STRENGTH AS IT RAPIDLY MOVES NORTHEASTWARD EAST OF TAIWAN. MODEL GUIDANCE BEYOND TAU 72 DIVERGES SIGNIFICANTLY, WITH TWO BASIC SCENARIOS. THE EGRR AND ECMWF FAVOR TAKING THE SYSTEM INTO THE SOUTH CHINA SEA AND KEEPING IT BELOW 20N LATITUDE THROUGH TAU 120. THE OTHER SOLUTION FAVORED BY THE REMAINDER OF AVAILABLE MODEL TRACKS, RECURVES THE SYSTEM AROUND THE RIDGE AXIS AND TRACKS IT NORTHEAST PARALLEL THE RYUKU ISLANDS, VARYING IN THE SPEED OF ADVANCE BUT GENERALLY AGREEING ON THE TRACK. THE SPREAD IN THE GUIDANCE AT TAU 120 IS 965 NM WITH MOST OF THIS COMPRISING ALONG- TRACK SPREAD. THE JTWC FORECAST LIES NEAR THE MULTI-MODEL CONSENSUS TRACK BUT SLOWER THAN THE CONSENSUS TRACK SPEED. THE HIGH DEGREE OF UNCERTAINTY IN THE TRACK SPREAD AND SHARPNESS OF THE RECURVE LENDS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.// NNNN NNNN