MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (SANBA) WARNING NR 13// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 02W (SANBA), LOCATED APPROXIMATELY 67 NM WEST- NORTHWEST OF ANGAUR, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE CENTRAL DEEP CONVECTION HAS DISSIPATED SOME AND THE FLARING IS STARTING TO REVEAL A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE ANIMATED LOOP AND AN 111741Z 37GHZ SSMI MICROWAVE IMAGE. THE AFOREMENTIONED MICROWAVE IMAGE SHOWS WEAK BANDING WRAPPING INTO A CENTRAL NOTCH FEATURE. THE INITIAL INTENSITY OF 35 KNOTS IS HEDGED SLIGHTLY ABOVE CONCURRENT DVORAK INTENSITY ESTIMATES OF T2.0 (30 KNOTS) FROM PGTW AND RJTD. ENVIRONMENTAL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF MODERATE (15-20 KNOT) VERTICAL WIND SHEAR AND IS TRACKING THROUGH AN AREA OF WARM (29 CELSIUS) SEA SURFACE TEMPERATURES. UPPER LEVEL ANALYSIS REVEALS THAT THE SYSTEM HAS STRONG POLEWARD OUTFLOW ENHANCED BY MID-LATITUDE WESTERLIES. TS 02W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 02W WILL TRACK GENERALLY WEST-NORTHWESTWARD ALONG AN EXTENSION OF THE STR TOWARD THE SOUTHERN PHILIPPINES, MAKING LANDFALL AROUND TAU 30. MARGINALLY FAVORABLE ENVIRONMENTAL CONDITIONS WILL ALLOW FOR ADDITIONAL INTENSIFICATION UP TO 45 KNOTS PRIOR TO LANDFALL. ONCE OVERLAND, THE SYSTEM WILL WEAKEN SLIGHTY AND A BUILDING EXTENSION OF THE STR WILL CAUSE THE SYSTEM TO TRACK WESTWARD AND INTO THE SULU SEA. MARGINAL CONDITION OVER THE SULU SEA WILL ALLOW THE SYSTEM TO MAINTAIN WEAK TROPICAL STORM STRENGTH AS IT TRACKS SOUTH OF PUERTO PRINCESA. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72, LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST. C. AFTER TAU 72, TS SANBA WILL TRACK MORE NORTHWESTWARD, AS THE STR RECEDES AND THE SYSTEM ROUNDS THE SOUTHWESTERN PERIPHERY OF THE EXTENSION. MARGINAL CONDITIONS IN THE SOUTH CHINA SEA, THE RESULT OF A COLD SURGE, WILL CAUSE THE SYSTEM TO GRADUALLY WEAKEN TO 30 KNOTS BY TAU 120. AVAILABLE DYNAMIC MODEL GUIDANCE SPREADS SIGNIFICANTLY IN BOTH TRACK DIRECTION AND ALONG TRACK SPEED, SPECIFICALLY IN THE TURN TO THE NORTHWEST. THE LARGE SPREAD IN MODEL GUIDANCE AFTER TAU 72 LENDS LOW CONFIDENCE IN THE LONG RANGE JTWC TRACK FORECAST.// NNNN NNNN