WDPN31 PGTW 251500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) 
WARNING NR 03//
RMKS//
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. AS EXPECTED MODERATE EASTERLY VERTICAL WIND SHEAR (VWS) AND AN 
INVERTED, UPPER LEVEL TROUGH DIRECTLY OVERHEAD HAVE HAMPERED 
AGGRESSIVE CONSOLIDATION AND INTENSIFICATION OF TD 17W (SEVENTEEN). 
THE UPPER LEVEL RIDGE AXIS THAT HAD BEEN BUFFERING HIGHER VWS HAS 
SINCE SHIFTED NORTH, ALLOWING FOR STRONG EASTERLIES TO FILTER IN 
OVER THE SYSTEM. THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS ALSO 
BECOME MORE AND MORE EXPOSED OVER THE LAST 12 HOURS, AND IS NOW 
LOCATED MORE THAN 100 NM TO THE EAST OF THE DEEPEST CONVECTION THAT 
IS NOW AFFECTING PARTS OF THE NORTHERN PI. NONETHELESS, CONVECTION 
HAS DEEPENED OVER THE PAST 12 HOURS, THOUGH SIGNIFICANTLY WEST OF 
THE LLCC AND PERHAPS DUE TO OROGRAPHIC INFLUENCES AND/OR STRONG 
SURFACE CONVERGENCE EVIDENT IN A 250951Z QUIKSCAT IMAGE. THE SAME 
QUIKSCAT IMAGE JUSTIFIES THE LOCATION OF THE LLCC, AS WELL AS THE 30 
KNOT INITIAL INTENSITY. THE FEW AVAILABLE OBSERVATIONS FROM LUZON, 
IN AND AROUND THE MANILA REGION, REPORT SEA LEVEL PRESSURE NEAR 1005 
MB, WITH WINDS GENERALLY OUT OF THE WEST AT 05 TO 10 KNOTS. THE 
DISTURBANCE HAS CONTINUED TO TRACK GENERALLY WEST TO WEST-
NORTHWESTWARD AT 09 KNOTS ALONG THE SOUTH SIDE OF THE MID-LEVEL 
SUBTROPICAL RIDGE TO THE NORTH. 
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN FORECAST REASONING OR PHILOSOPHY. 
   B. THE SYSTEM WILL CONTINUE TO TRACK GENERALLY WESTWARD TOWARDS 
LUZON, MAKING LANDFALL SHORTLY AFTER TAU 24. THE LLCC IS EXPECTED TO 
WEAKEN SOME, BUT IMPROVED UPPER LEVEL CONDITIONS AND FAVORABLE SEA 
SURFACE TEMPERATURES WILL PROMOTE REINTENSIFICATION AS THE LLCC 
EMERGES INTO THE SOUTH CHINA SEA. ALL THE WHILE THE SYSTEM WILL 
CONTINUE TO TRACK MORE OR LESS DUE WEST UNDER THE INFLUENCE OF 
STRONG RIDGING TO THE NORTH. IN GENERAL, THE PREVIOUS 2 MODEL RUNS 
CONSISTENTLY RESOLVE A MORE ZONAL MID-LATITUDE PATTERN THROUGH THE 
NEXT 3 DAYS, WHICH SHOULD ALLOW THE MID-LEVEL SUBTROPICAL RIDGE TO 
THE NORTH TO REMAIN FIRMLY IN PLACE AND FACILITATE WESTWARD 
MOVEMENT. THE AVAILABLE CONSENSUS MEMBERS ARE ALL IN FAIRLY GOOD 
AGREEMENT WITH THIS STRAIGHT-RUNNING/WESTWARD TRACK SCENARIO, WITH 
THE EXCEPTION OF NOGAPS. NOGAPS IS STILL EXCESSIVELY DEEPENING A MID-
LATITUDE TROUGH, WHICH EFFECTIVELY BREAKS DOWN THE RIDGE TO THE 
NORTH AND STEERS THE SYSTEM FURTHER POLEWARD. 
   C. THE EXTENDED FORECAST THROUGH DAY 4 AND 5 CALLS FOR MUCH THE 
SAME PHILOSOPHY AS THE FIRST 72 HOURS. THE STORM WILL CONTINUE TO 
TRACK WESTWARD TOWARDS VIETNAM AND REINTENSIFY, BUT IS NOW EXPECTED 
TO REACH A PEAK INTENSITY OF AROUND 50 KNOTS. WARMER WATERS IN THE 
GULF OF TONKIN WILL HELP THE CYCLONE TO DEEPEN JUST OFFSHORE. BY DAY 
5 THE SYSTEM WILL COME ASHORE AND BEGIN TO WEAKEN. 
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