WDPN32 PGTW 100300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (VAMCO) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 25W (VAMCO), LOCATED APPROXIMATELY 444 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT TS 25W HAS CONSOLIDATED INTO A WELL DEFINED SYSTEM, WITH DEEP FLARING CONVECTION ALONG THE SOUTHERN SEMI-CIRCLE AND SPIRAL BANDING EXTENDING ACROSS THE NORTHERN PORTION OF THE SYSTEM WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED UPON THE BANDING FEATURES PRESENT IN A 092217Z SSMIS 37GHZ IMAGE. THE INITIAL INTENSITY IS ASSESSED AT 35 KTS WITH HIGH CONFIDENCE BASED ON MULTI- AGENCY DVORAK INTENSITY ESTIMATES OF T2.0 (30 KNOTS) FROM PGTW AND RJTD, AND AN ADVANCED DVORAK TECHNIQUE (ADT) CURRENT INTENSITY ESTIMATE OF T2.8 (38 KTS). TS 25W IS TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM REMAINS IN A FAVORABLE POSITION FOR INTENSIFICATION WITH LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS) AND STRONG DIVERGENCE ALOFT ASSOCIATED WITH A POINT SOURCE OVER THE VORTEX CENTER. ADDITIONALLY, SEA SURFACE TEMPERATURES (SST) REMAIN WARM (29-30 CELSIUS) AND OCEAN HEAT CONTENT (OHC) REMAINS HIGH (120-140 KJ/CM^2). 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. IN THE NEAR TERM, TS VAMCO WILL CONTINUE TO TRACK NORTHWESTWARD THROUGH TAU 12 AND TURN WEST-NORTHWESTWARD BY TAU 24 AS THE STR BUILDS AND EXTENDS TOWARDS THE WEST ALONG THE 25TH PARALLEL, EFFECTIVELY BLOCKING THE POLEWARD MOVEMENT. THE SYSTEM WILL CONTINUE TO CONSOLIDATE AND INTENSIFY TO 90 KTS BY TAU 36 DUE TO A HIGHLY FAVORABLE ENVIRONMENT WITH CONTINUED LOW (5-10 KTS) VWS, HIGH SST AND OHC, AND IMPROVING DIVERGENCE ALOFT. DUE TO THE HIGHLY FAVORABLE ENVIRONMENT, THERE IS A DISTINCT POSSIBILITY OF RAPID INTENSIFICATION DURING THIS TIME. THE SYSTEM IS THEN FORECAST TO CROSS LAMON BAY AND MAKE LANDFALL ALONG THE CENTRAL LUZON COAST DUE EAST OF MANILA NEAR TAU 36 BEFORE REEMERGING INTO THE OPEN WATERS OF THE SOUTH CHINA SEA NEAR TAU 48. WHILE THE SYSTEM CROSSES LUZON BETWEEN TAU 36 AND TAU 48, INTERACTION WITH THE RUGGED TERRAIN WILL INDUCE WEAKENING DUE TO FRICTIONAL EFFECTS. AFTER TAU 48, TS VAMCO WILL ENTER THE SOUTH CHINA SEA (SCS) AND SUBSEQUENTLY INTENSIFY 75 KTS BY TAU DUE TO A FAVORABLE ENVIRONMENT AT THIS TIME. DYNAMIC TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT THROUGH THE TURN WESTWARD, WITH SOME SLIGHT DIFFERENCES IN THE SHARPNESS OF THE TURN LEADING TO A SPREAD OF 82 NM AT TAU 48 THROUGH WHICH INCREASES SLIGHTLY TO 86 NM BY TAU 72. THE TIGHT AGREEMENT IN THE MODEL SOLUTIONS LENDS OVERALL GOOD CONFIDENCE IN THE INITIAL PORTION OF THE JTWC FORECAST TRACK WITH IS PLACED NEAR THE JTWC MULTI-MODEL CONSENSUS. C. AFTER TAU 72, THE SYSTEM WILL TRACK GENERALLY NORTHWESTWARD THROUGH TAU 120 UNDER THE STEERING INFLUENCE OF THE DEEP-LAYER STR WHICH WILL RETREAT SLIGHTLY NORTHEAST DURING THIS TIME. AS THE SYSTEM TRACKS OVER THE SOUTH CHINA SEA IT WILL BEGIN TO WEAKEN AFTER TAU 72 DUE TO DECREASING SST AND SIGNIFICANTLY LOWER OHC, ULTIMATELY FALLING TO AN INTENSITY OF 60 KTS BY TAU 120. NUMERICAL MODEL GUIDANCE DEPICTS INCREASING UNCERTAINTY AFTER TAU 72 WITH CROSS-TRACK SPREAD INCREASING TO 210 NM BY TAU 120. THIS SLIGHT DIVERGENCE IN MODEL SOLUTIONS DURING THIS EXTENDED PORTION OF THE JTWC FORECAST TRACK ARISES DUE TO UNCERTAINTY IN THE EXTENT AND TIMING OF THE REPOSITIONING OF THE AFOREMENTIONED STEERING RIDGE. SPECIFICALLY, THE DETERMINISTIC NAVGEM AND AFUM SOLUTIONS, ALONG WITH THE UKMET ENSEMBLE SOLUTION, DEPICT A RECURVATURE SCENARIO WITH THE VORTEX TRAVELING WEST-NORTHWESTWARD TO NORTHWESTWARD AND THE REMAINING MODEL MEMBERS PROVIDING A GENERALLY WESTWARD SOLUTION. THIS INCREASING DIVERGENCE IN MODEL SOLUTIONS LENDS OVERALL POOR CONFIDENCE IN THIS EXTENDED PORTION OF THE JTWC FORECAST TRACK WHICH IS LAID SLIGHTLY SOUTH OF THE MULTI-MODEL CONSENSUS.// NNNN