WDPN31 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (DUJUAN) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 01W (DUJUAN), LOCATED APPROXIMATELY 747 NM 
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 04 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
INDICATES A SLOWLY-CONSOLIDATING SYSTEM WITH A PERSISTENT MASS OF 
DEEP CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC) 
WHICH IS LOCATED UNDER THE EASTERN EDGE OF THE DEEP CONVECTION. A 
182140Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE IMAGE DEPICTS SHALLOW 
BANDING WRAPPING INTO THE LLCC WITH A CURVED BAND OF DEEP CONVECTION 
OVER THE WEST AND NORTHWEST QUADRANTS. OVERALL, THERE IS FAIR 
CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS 
ASSESSED AT 45 KNOTS BASED ON DVORAK ESTIMATES OF T3.0 (45 KNOTS) 
FROM PGTW, KNES AND RCTP. ADDITIONALLY, THE 180140Z ADT ESTIMATE HAS 
INCREASED TO 3.1 (47 KNOTS). UPPER-LEVEL ANALYSIS INDICATES A 
MARGINALLY-FAVORABLE ENVIRONMENT WITH MODERATE (20 KNOTS) 
SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY ROBUST POLEWARD 
OUTFLOW, WHICH HAS ALLOWED DEEP CONVECTION TO CONSOLIDATE OVER THE 
LLCC OVER THE PAST 12 HOURS. 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 
24 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 THROUGH TAU 72 WITH LANDFALL OCCURRING NEAR TAU 48. TS 
01W WILL INTENSIFY SLOWLY TO A PEAK INTENSITY OF 55 KNOTS BY TAU 24-
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 20 KNOTS BY TAU 120. 
NUMERICAL MODEL GUIDANCE DIVERGES AND IS IN POOR AGREEMENT IN THE 
EXTENDED PERIOD WITH A LARGE SPREAD OF 565NM 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 ERRATIC 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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