WDPN31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (ONE) WARNING 
NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 01W (ONE), LOCATED APPROXIMATELY 335 NM
SOUTH-SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 18
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY
DEPICTS FLARING CONVECTION CONFINED TO THE NORTHWEST OF THE LOW LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS BASED ON A 021047Z
91 GHZ SSMIS MICROWAVE IMAGE SHOWING CONVECTION IN THE NORTHWEST
QUADRANT OF TD 01W. THE INITIAL INTENSITY ESTIMATE OF 30 KNOTS IS
HEDGED ABOVE A PGTW DVORAK ESTIMATE OF T1.0 (25 KNOTS) AND A RJTD
DVORAK ESTIMATE OF T1.5 (25 KNOTS) BUT WELL BELOW A 021128Z SATCON
ESTIMATE OF 46 KNOTS. ENVIRONMENTAL ANALYSIS SHOWS FAVORABLE VERTICAL
WIND SHEAR (10 TO 15 KNOTS). HOWEVER, STRONG EASTERLY WINDS ALOFT ARE
INHIBITING DEVELOPMENT. SEA SURFACE TEMPERATURES REMAIN FAVORABLE,
NEAR 29 DEGREES CELSIUS. TD 01W IS TRACKING WESTWARD ACROSS THE SULU
SEA UNDER THE STEERING INFLUENCE OF AN EAST-WEST ORIENTED SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 01W IS FORECAST TO CONTINUE TRACKING WESTWARD UNDER THE 
INFLUENCE OF THE STR WHICH IS LOCATED TO THE NORTH AND GRADUALLY 
INCREASE IN INTENSITY TO 35 KNOTS BY TAU 24. MODERATE VERTICAL WIND 
SHEAR WILL PREVENT ADDITIONAL INTENSIFICATION. AS TD 01W ENTERS THE 
SOUTH CHINA SEA IT WILL INITIALLY ENCOUNTER FAVORABLE SEA SURFACE
TEMPERATURES (28 TO 29 DEGREES CELSIUS). HOWEVER, AS TD 01W TRACKS
WESTWARD IT WILL ENCOUNTER COOLER SEA SURFACE TEMPERATURES WHICH WILL
LIMIT DEVELOPMENT. SEA SURFACE TEMPERATURES WILL BECOME UNFAVORABLE
(25 DEGREES CELSIUS) JUST AFTER TAU 36. SHORTLY BEFORE TAU 48, TD 01W
WILL MAKE LANDFALL OVER SOUTHERN VIETNAM AND SLOW IN FORWARD SPEED.
BY TAU 48, TD 01W WILL DISSIPATE OVER VIETNAM DUE TO LAND 
INTERACTION. NUMERICAL MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT 
THROUGH TAU 24. BEYOND TAU 24, MODEL GUIDANCE AGREEMENT HAS IMPROVED 
BUT THERE IS A LARGE SPREAD AS TD 01W APPROACHES VIETNAM. OVERALL, 
THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK DUE TO THE LARGE 
SPREAD IN MODEL SOLUTIONS AFTER TAU 24.//
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