WDPN31 PGTW 111500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (SANBA)
WARNING NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 17W (SANBA), LOCATED APPROXIMATELY 725 NM
EAST OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT 12
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY 
SHOWS THE SYSTEM HAS BECOME MORE ORGANIZED AS CONVECTIVE BANDING
DEEPENED AND WRAPPED TIGHTER INTO THE LOW LEVEL CIRCULATION CENTER.
THE INITIAL POSITION IS EXTRAPOLATED FROM A 111050Z SSMI-S MICROWAVE
IMAGE WITH POOR CONFIDENCE. THE INITIAL INTENSITY IS BASED ON DVORAK
ESTIMATES RANGING FROM 35 TO 42 KNOTS FROM PGTW AND RJTD. UPPER LEVEL
ANALYSIS INDICATES THE SYSTEM IS JUST TO THE SOUTH OF A RIDGE AXIS IN
AN AREA OF LIGHT (05-10 KNOT) VERTICAL WIND SHEAR. IT HAS MAINTAINED
A MESOSCALE ANTICYCLONE THAT IS RESPONSIBLE FOR THE RADIAL OUTFLOW
THAT IS EVIDENT ON ANIMATED WATER VAPOR IMAGERY. THE SAME ANIMATION
ALSO SHOWS AN ENHANCED POLEWARD CHANNEL FEEDING INTO A TROPICAL
UPPER TROPOSPHERIC TROUGH TO THE NORTHEAST. THE CYCLONE IS TRACKING
ALONG THE WESTERN PERIPHERY OF A NEAR-EQUATORIAL RIDGE TO THE EAST.  
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 17W IS EXPECTED TO CONTINUE TRACKING NORTHWARD AND STEADILY
INTENSIFY AS UPPER LEVEL CONDITIONS, IN ADDITION TO WARM SEA SURFACE
TEMPERATURES (28-30 CELSIUS), PERSIST. THERE IS A POSSIBILITY THAT TS
17W WILL INTENSIFY AT A HIGHER THAN NORMAL RATE. 
   C. AFTER TAU 72, A BUILDING SUBTROPICAL RIDGE EAST OF JAPAN WILL
ASSUME STEERING WITH NO SIGNIFICANT CHANGE IN THE TRAJECTORY OF THE
FORECAST TRACK. FAVORABLE ENVIRONMENTAL CONDITIONS WILL PERSIST
RESULTING IN CONTINUED STEADY INTENSIFICATION, PEAKING AT 100 KTS BY
TAU 96. THE AVAILABLE NUMERICAL MODEL GUIDANCE HAS COME INTO BETTER
AGREEMENT WITH JGSM AS THE RIGHT OUTLIER DURING THE FIRST HALF OF THE
FORECAST. A MINOR ADJUSTMENT TO THE LEFT OF CONSENSUS IS REFLECTED IN
THE TRACK FORECAST TO OFFSET THE UNLIKELY RIGHTWARD BIAS OF JGSM. THE
CONFIDENCE IN THIS FORECAST IS HIGH.    //
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