WDPN33 PGTW 040300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 21W WARNING NR 20//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION 21W (HIGOS) HAS SLOWED AS IT CROSSED
THE EXTREME EASTERN PART OF HAINAN ISLAND WHILE WEAKENING. THE
LOW LEVEL CIRCULATION HAS BECOME INCREASINGLY EXPOSED TO THE
EAST OF THE BULK OF REMAINING CONVECTION AS THE SYSTEM DEGRADES.
   B. TD 21W IS TRACKING NORTH-NORTHWESTWARD UNDER THE STEERING
INFLUENCE OF A WEAK EXTENSION OF THE LOW LEVEL STR POSITIONED TO
THE NORTHEAST AND IS CURRENTLY EMERGING BACK INTO WATER AFTER
TRANSITING OVER HAINAN. SURFACE PRESSURE OBSERVATIONS FROM HAINAN
OF 1003 MB SUPPORT A 25 KNOT CIRCULATION, WHILE A PARTIAL QSCAT
032347Z PASS INDICATES WINDS NEAR THE CENTER AS HIGH AS 30 KNOTS
(THOUGH RAIN FLAGGED). THE SYSTEM HAS BECOME INCREASINGLY DIS-
ORGANIZED DUE TO LAND INTERACTION AND MODERATE NORTHERLY VERTICAL
WIND SHEAR. MUCH OF THE LIMITED REMAINING POCKETS OF DEEP CONVECTION
ARE A CONSEQUENCE OF OROGRAPHIC LIFTING AND NOT THE CIRCULATION
ITSELF.
3. FORECAST REASONING.
   A. THE FORECAST HAS BEEN DECREASED TO 36 HOURS AND HAS BEEN
SHIFTED EASTWARD, CLOSER TO THE CHINESE COASTLINE.
   B. TD 21W WILL TRACK GENERALLY POLEWARD IN RESPONSE TO FURTHER
EROSION OF THE ALREADY WEAK EXTENSION OF THE SUBTROPICAL RIDGE
TO THE NORTH. THE TROUGH RESPONSIBLE FOR BREAKING DOWN THE
RIDGE AND PROMPTING RECURVATURE IS CURRENTLY ANALYZED OVER
CENTRAL CHINA, WITH THE MAJORITY OF THE MODEL FIELDS AND THE
FORECAST TRACK REFLECTING THE BREAK WITHIN THE NEXT 12 HOURS. SHORTLY
AFTER TAU 12, THE SYSTEM WILL TRACK ASHORE MAINLAND CHINA AS A
WEAK TROPICAL DEPRESSION. AFTER WHICH, TD 19W WILL TRACK GENERALLY
NORTHEASTWARD AND DISSIPATE PRIOR TO EMERGING INTO THE SOUTH CHINA
SEA, NEAR TAU 24. A 04000z SKEW-T SOUNDING FROM TAIWAN INDICATES
SOUTHEASTERLY FLOW FROM THE SURFACE TO 700 MB, SUGGESTING A MORE
POLEWARD (AND MORE INLAND) TRACK THAN THE MODEL TRACKERS INDICATE,
AND SUBSEQUENTLY SUPPORTS COMPLETE DISSIPATION OVER LAND AS THE
SYSTEM BEGINS TO RECURVE.
FORECAST TEAM: BRAVO//