WDPN31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (ONE) WARNING 
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 01W (DAJUAN), LOCATED APPROXIMATELY 787 NM 
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 
05 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
REVEALS A FULLY EXPOSED, WELL-DEFINED LOW LEVEL CIRCULATION CENTER 
(LLCC), WITH FLARING DEEP CONVECTION WITH OVERSHOOTING TOPS SHEARED 
TO THE WEST OF THE LLCC, LENDING HIGH CONFIDENCE TO THE INITIAL 
POSITION. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS WITH HIGH 
CONFIDENCE BASED ON DVORAK CURRENT INTENSITY ESTIMATES BETWEEN T2.0 
(30 KTS, RJTD AND KNES) AND T2.5 (35 KTS, PGTW) AND AN ADT ESTIMATE 
OF 2.5 (35 KTS). UPPER-LEVEL ANALYSIS INDICATES A MARGINAL 
ENVIRONMENT WITH MODERATE (15-20 KNOTS) EASTERLY VERTICAL WIND SHEAR 
(VWS) OFFSET BY ROBUST DIFFLUENT POLEWARD OUTFLOW. SST VALUES REMAIN 
CONDUCIVE AT 29-30C. TS 01W IS MOVING SLOWLY WESTWARD IN A GENERALLY 
WEAK STEERING PATTERN, COCOONED WITHIN A COL AREA BETWEEN A 
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST AND A SECOND TO THE 
SOUTHWEST.
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) RESULTING FROM THE PRESENCE 
OF A MAJOR 
SHORTWAVE TROUGH EXTENDING FROM JAPAN TO EAST OF TAIWAN. OVER THE 
NEXT 36 HOURS, THE SHORTWAVE TROUGH WILL MOVE TO THE NORTHEAST AND 
FILL, ALLOWING FOR THE STR TO THE EAST TO BUILD IN TO THE NORTHEAST 
OF TS 01W, ALLOWING THE SYSTEM TO MOVE SLOWLY WESTWARD THROUGH TAU 
36. AFTER TAU 48, THE STR AXIS REORIENTS SLIGHTLY TO A MORE 
NORTHWEST-SOUTHEAST ORIENTATION, AND IN RESPONSE TS 01W WILL TURN TO 
A MORE WEST-NORTHWEST TRACK THROUGH TAU 72. LANDFALL IS EXPECTED 
NEAR TAU 60 ALONG THE FAR NORTHEAST COAST OF MINDANAO. NUMERICAL 
MODEL GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 48, WITH INCREASING 
UNCERTAINTY BY TAU 72. THE UKMET DETERMINISTIC AND ENSEMBLE 
SOLUTIONS CONTINUE TO SHOW AN UNLIKELY POLEWARD TRACK TO THE EAST OF 
THE PHILIPPINES, WHILE THE GFS SOLUTION SHOWS AN EQUALLY UNLIKELY 
DUE TO WEST TRACK. DISCOUNTING THE OUTLIERS, THE REMAINDER OF THE 
CONSENSUS MEMBERS LIE CLOSE TO THE CONSENSUS MEAN, WITH A 150NM 
SPREAD IN SOLUTIONS AT TAU 72. AS DISCUSSED EARLIER, VWS IS 
CURRENTLY DOMINATING THE SYSTEM. HOWEVER, VWS IS EXPECTED TO WEAKEN 
SLIGHTLY OVER THE NEXT DAY OR SO, WHICH WILL ALLOW THE SYSTEM TO 
REESTABLISH CORE CONVECTION, ENABLING A SLOW BUT STEADY 
INTENSIFICATION TO A PEAK OF 50 KNOTS BY TAU 48. THERE IS 
CONSIDERABLE UNCERTAINTY HOWEVER IN THE INTENSIFICATION FORECAST DUE 
TO THE STEADY EASTERLY VWS AND HOW MUCH THE STRONG POLEWARD OUTFLOW 
WILL OFFSET THIS SHEAR. 
   C. THE SYSTEM IS FORECAST TO CONTINUE TRACKING ALONG THE WESTERN 
BOUNDARY OF THE DEEP-LAYER STR LOCATED TO THE EAST THROUGH THE 
EXTENDED FORECAST PERIOD. BY TAU 72 THE SYSTEM IS EXPECTED TO BE IN 
THE BOHOL SEA, AND WILL TRACK NORTHWESTWARD OVER THE MAJOR ISLANDS 
OF THE SOUTHWEST PHILIPPINES, REEMERGING INTO THE INTO THE NORTHERN 
SULU SEA BY TAU 96, AND INTO THE SOUTH CHINA SEA BEFORE TAU 120. THE 
COMBINED EFFECTS OF TERRAIN INTERACTION, INCREASING VWS, DECREASED 
UPPER-LEVEL OUTFLOW AND THE ENTRAINMENT OF DRIER AIR WILL WEAKEN THE 
SYSTEM TO 25 KNOTS BY TAU 120. EVEN WHEN DISCOUNTING THE UKMET, 
UKMET ENSEMBLE SHOWING THE UNLIKELY POLEWARD TRACK, AND THE GFS 
DEPICTING A STRAIGHT WESTERLY TRACK, NUMERICAL MODEL GUIDANCE IS IN 
POOR AGREEMENT AFTER TAU 72, WITH A 450NM SPREAD IN MODEL SOLUTIONS 
BY TAU 120. THE JTWC FORECAST TRACK REMAINS CONSISTENT WITH THE 
PREVIOUS FORECAST AND LIES NEAR THE ECMWF SOLUTION. OVERALL, THERE 
IS POOR CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH LIES SOUTH OF 
THE MULTI-MODEL CONSENSUS, NEAR THE ECMWF SOLUTION.//
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