WDPN31 PGTW 182100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (DUJUAN) WARNING 
NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 01W (DUJUAN), LOCATED APPROXIMATELY 775 NM
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 02 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY REVEALS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER 
(LLCC) POSITIONED UNDER THE SOUTHEAST EDGE OF AN AREA OF EXPANSIVE 
DEEP CONVECTION. UNFORTUNATELY, THERE ARE NO USEFUL MICROWAVE IMAGES 
TO HELP LOCATE THE CENTER, THEREFORE, THERE IS FAIR CONFIDENCE IN 
THE INITIAL POSITION, WHICH APPEARS TO BE QUASI-STATIONARY OR SLOW 
MOVING. THE INITIAL INTENSITY REMAINS ASSESSED AT 35 KNOTS BASED ON 
A DVORAK ESTIMATES OF T2.5 (35 KNOTS) FROM ALL AGENCIES. UPPER-LEVEL 
ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH MODERATE 
(20 KNOTS) SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY 
DIFFLUENT EASTERLY FLOW AND ROBUST POLEWARD OUTFLOW. SST VALUES 
REMAIN CONDUCIVE AT 29-30C. TS 01W IS TRACKING ALONG THE SOUTHWEST 
PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO 
THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE IN THE FORECAST PHILOSOPHY FROM 
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 01W IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT SOUTH OF 
A BREAK IN THE SUBTROPICAL RIDGE (STR) ASSOCIATED WITH A MAJOR 
SHORTWAVE TROUGH CURRENTLY OVER AND SOUTH OF JAPAN. IN GENERAL, THE 
SYSTEM WILL TRACK SLOWLY WESTWARD TO WEST-NORTHWESTWARD THROUGH TAU 
36 UNTIL THE MAJOR TROUGH SHIFTS EASTWARD AND ZONAL FLOW 
PREDOMINATES. THIS WILL ALLOW THE STR TO RE-BUILD NORTHEAST AND 
NORTH OF THE SYSTEM, WHICH WILL ALLOW THE SYSTEM TO ACCELERATE WEST-
NORTHWESTWARD WITH LANDFALL OCCURRING NEAR TAU 48. WITH THE 
EXCEPTION OF THE UKMET DETERMINISTIC AND UKMET ENSEMBLE MEAN 
SOLUTIONS, NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT WITH A 
175NM SPREAD IN SOLUTIONS AT TAU 72. TS 01W WILL INTENSIFY STEADILY 
TO A PEAK INTENSITY OF 50 KNOTS BY TAU 36 UNDER GENERALLY FAVORABLE 
CONDITIONS, ESPECIALLY STRONG POLEWARD OUTFLOW. HOWEVER, THERE IS 
SOME UNCERTAINTY IN THE PEAK INTENSITY DUE TO THE PERSISTENT 
MODERATE VWS.    
   C. AFTER TAU 72, TS 01W WILL CONTINUE TO TRACK ACROSS THE 
PHILIPPINE ARCHIPELAGO, AND BY TAU 96, WILL REACH THE SOUTH CHINA 
SEA OFF THE ISLAND OF MINDORO. INTERACTION WITH THE ISLANDS AND 
INCREASED VWS WILL WEAKEN THE SYSTEM DOWN TO 25 KNOTS BY TAU 120. 
NUMERICAL MODEL GUIDANCE DIVERGES AND IS IN POOR AGREEMENT IN THE 
EXTENDED PERIOD WITH A LARGE SPREAD OF 530NM AT TAU 120 (MINUS UKMET 
AND UKMET ENSEMBLE MEAN). THESE SOLUTIONS ARE RECURVING THE SYSTEM 
NORTHEASTWARD, WHICH IS UNLIKELY DUE TO THE STRONG LIKELIHOOD OF A 
RE-BUILDING STR AND ZONAL UPPER-LEVEL FLOW OVER THE EAST CHINA SEA. 
DUE TO THE QUASI-STATIONARY MOTION AND THE LARGE SPREAD IN MODEL 
SOLUTIONS, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH 
IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS.//
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