WDPN32 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI) 
WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 23W (ATSANI), LOCATED APPROXIMATELY 390 NM SOUTH 
OF KADENA AB, HAS TRACKED EAST-NORTHEASTWARD AT 04 KNOTS OVER THE 
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) 
SHOWS A QUASI-STATIONARY SYSTEM WITH FORMATIVE DEEP CONVECTIVE BANDS 
AND CYCLING CONVECTIVE ACTIVITY NEAR THE ASSESSED LOW LEVEL 
CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH FAIR 
CONFIDENCE BASED ON THE BANDING FEATURES WHICH ARE EVIDENT IN A 
031737Z ATMS MICROWAVE IMAGE. THE INITIAL INTENSITY IS ASSESSED AT 
35 KNOTS WITH FAIR CONFIDENCE BASED ON PGTW AND RJTD CURRENT 
INTENSITY ESTIMATES OF T2.5 AND A 031740Z ADVANCED DVORAK TECHNIQUE 
(ADT) ESTIMATE OF 37 KNOTS. THE OVERALL ENVIRONMENT REMAINS 
FAVORABLE FOR DEVELOPMENT WITH WARM (28 TO 29 DEGREE CELSIUS) SEA 
SURFACE TEMPERATURES (SST), LOW (5-10 KNOTS) VWS, AND MODERATE 
OUTFLOW OFFSET TO THE NORTHEAST. THE SYSTEM REMAINS ENTRENCHED IN A 
COL REGION WITH NO DOMINANT STEERING FLOW.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 23W IS EXPECTED TO FINALLY TURN BACK WEST AND THEN WEST-
NORTHWEST UNDER A WEAK STEERING ENVIRONMENT OVER THE NEXT 24 HOURS 
AS A STR LOCATED TO THE NORTHEAST BEGINS TO BUILD IN. BY TAU 36, THE 
STR BUILDS EVEN FURTHER WEST, AND WILL SERVE TO ACCELERATE TS 23W 
INTO THE LUZON STRAIT BY TAU 60, WITH A PEAK INTENSITY OF 60 KNOTS 
EXPECTED AT TAU 72. THE ENVIRONMENT IS EXPECTED TO REMAIN FAVORABLE 
THROUGH TAU 72 WITH GOOD OUTFLOW, LOW (5-10 KNOTS) VWS AND WARM (28-
29 DEGREE CELSIUS) SST VALUES. NUMERICAL MODELS ARE IN OVERALL GOOD 
AGREEMENT WITH A SPREAD OF 140NM AT TAU 72 DISCOUNTING THE NAVGEM 
SOLUTION, WHICH CONTINUES TO TAKE THE SYSTEM ON AN UNREALISTIC TRACK 
NORTH OVER TAIWAN AND INTO THE EAST CHINA SEA. THE JTWC FORECAST 
LIES NEAR THE MULTI-MODEL CONSENSUS SOLUTION THROUGH TAU 72 WITH 
FAIR CONFIDENCE DUE TO THE NEAR-TERM ERRATIC MOTION AND RESULTANT 
UNCERTAINTY IN THE TIMING OF THE TURN TO THE WEST.  
   C. AFTER TAU 72, THE SYSTEM BEGINS TO TRACK SOUTHWESTWARD AS TS 
23W TAKES STEERING FROM A SECOND STR LOCATED OVER INDOCHINA, WHICH 
HAS A MORE SOUTHWEST-NORTHEAST ORIENTATION. ADDITIONALLY, THE SYSTEM 
BEGINS TO FEEL THE IMPACT OF INCREASING VWS (15-30 KNOTS), 
DECREASING SST AND CONVERGENT FLOW ALOFT, LEADING TO A FAIRLY RAPID 
WEAKENING TREND. DYNAMIC MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT.
HOWEVER, NAVGEM TAKES THE SYSTEM INTO THE EAST CHINA SEA, WHILE THE 
AFUM SOLUTION TURNS DRAMATICALLY SOUTHWARD AFTER TAU 72. BOTH 
SOLUTIONS ARE CONSIDERED UNREALISTIC AND DISCOUNTED FROM THE MULTI-
MODEL CONSENSUS WHICH JTWC IS LAID ALONG. THERE IS OVERALL FAIR 
CONFIDENCE IN THE LATER JTWC TRACK FORECAST DUE TO THE CURRENT QUASI-
STATIONARY STATE AND THE OVERALL SPREAD IN THE GUIDANCE.// 
NNNN