WDPN32 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI) 
WARNING NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 23W (ATSANI), LOCATED APPROXIMATELY 398
NM SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED EASTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) 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 GOOD 
CONFIDENCE BASED ON THE BANDING FEATURES WHICH ARE EVIDENT IN A 
032154Z SSMIS MICROWAVE IMAGE AND MSI. THE INITIAL INTENSITY IS 
ASSESSED ABOVE PGTW AND RJTD CURRENT INTENSITY ESTIMATES OF T2.5, 
CLOSER IN LINE WITH A 032124Z SATCON ESTIMATE OF 47 KNOTS AND AN 
ADVANCED DVORAK ESTIMATE OF 45 KNOTS. ADDITIONALLY, A 040013Z 
SCATSAT PASS REINFORCES THE POSITION AND INTENSITY WITH A SWATH OF 
40-45 KNOT WINDS IN THE NORTHWEST QUADRANT. THE OVERALL ENVIRONMENT 
REMAINS FAVORABLE FOR DEVELOPMENT WITH WARM (28 TO 29 DEGREE 
CELSIUS) SEA SURFACE TEMPERATURES (SST), LOW (5-10 KNOTS) VERTICAL 
WIND SHEAR (VWS), AND MODERATE OUTFLOW OFFSET TO THE NORTH. 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 48, 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 CROSS-TRACK SPREAD OF 110NM 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 (20-30 KNOTS), 
DECREASING SST (26-27 DEGREES CELSIUS) 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 
TAIWAN, 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.// 
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