WDPN32 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (VAMCO) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 25W (VAMCO), LOCATED APPROXIMATELY 503 NM 
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 
06 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED 
SATELLITE IMAGERY (EIR) INDICATES THAT THE SYSTEM IS CONTINUING TO 
CONSOLIDATE, WITH DEEP CONVECTION ACROSS THE SOUTHERN SEMI-CIRCLE AND 
SPIRAL BANDING EXTENDING ACROSS THE NORTHERN PORTION OF THE SYSTEM 
WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER (LLCC). A 091727Z ATMS 
88.2GHZ AND A 091729Z AMSR2 89GHZ MICROWAVE IMAGE FURTHER EMPHASIZE 
THE CONSOLIDATION OF THE SYSTEM OVER THE PAST SIX HOURS WITH 
CONVECTIVE BANDING FORMING ALONG THE SOUTHEASTERN PERIPHERY. THE 
INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE IN THE CENTER OF THE 
LLCC INDICATED WITHIN THE AFOREMENTIONED ATMS MICROWAVE IMAGE. THE 
INITIAL INTENSITY IS SET AT 30 KTS WITH HIGH CONFIDENCE BASED ON 
MULTI-AGENCY DVORAK INTENSITY ESTIMATES OF T1.5-T2.0 (25-30 KNOTS) 
FROM PGTW AND RJTD, AND AN ADVANCED DVORAK TECHNIQUE (ADT) ESTIMATE 
OF T2.4 (34 KTS). TD 25W CONTINUES TO TRACK NORTHWESTWARD ALONG THE 
SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE 
NORTHEAST. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS IN A 
FAVORABLE POSITION FOR INTENSIFICATION WITH LOW (5-10 KTS) VERTICAL 
WIND SHEAR (VWS), STRONG DIVERGENCE ALOFT ASSOCIATED WITH A POINT 
SOURCE OVER THE VORTEX CENTER, WARM (29-30 CELSIUS) SEA SURFACE 
TEMPERATURES (SST), AND HIGH (120-140 KJ/CM^2) OCEAN HEAT CONTENT 
(OHC) AND STRONG EQUATORWARD AND MODERATE WESTWARD OUTFLOW. 
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR TERM, TD VAMCO WILL CONTINUE TO TRACK NORTHWESTWARD 
THROUGH TAU 12 BEFORE SLOWLY TURNING ONTO A WEST-NORTHWESTWARD TRACK 
BY TAU 24 AS THE STR BUILDS AND EXTENDS TOWARDS THE WEST ALONG THE 
25TH PARALLEL, EFFECTIVELY BLOCKING ANY FURTHER POLEWARD MOVEMENT. 
THROUGH THE NEXT 48 HOURS, THE SYSTEM WILL CONTINUE TO CONSOLIDATE 
AND INTENSIFY TO 105 KTS BY TAU 48 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 FURTHER 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 48 BEFORE REEMERGING INTO THE OPEN WATERS OF THE SOUTH CHINA SEA 
BEFORE TAU 72. AS THE SYSTEM CROSSES LUZON, INTERACTION WITH THE 
RUGGED TERRAIN WILL INDUCE SIGNIFICANT WEAKENING, WITH A SUBSEQUENT 
INTENSIFICATION TO 75 KTS BY TAU 72 OVER THE SOUTH CHINA SEA. 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 90NM AT TAU 48 THROUGH WHICH INCREASES SLIGHTLY 
TO 120 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 CONTINUE TO TRACK WESTWARD 
THROUGH TAU 120 UNDER THE STEERING INFLUENCE OF THE DEEP-LAYER STR 
TO THE NORTH. 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 360NM BY TAU 120. THE DIVERGENCE 
IN MODEL SOLUTIONS DURING THIS EXTENDED PORTION OF THE JTWC FORECAST 
TRACK ARISES DUE TO UNCERTAINTY IN THE EXTENT AND TIMING OF THE WESTWARD 
BUILDING OF THE STR TO THE NORTH. 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