Tropical Storm SAUDEL Advisory mié, 21-10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (SAUDEL) WARNING NR
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 19W (SAUDEL), LOCATED APPROXIMATELY 196 NM
NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 16 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY AND A 20/2321Z SSMIS 91GHZ IMAGE INDICATE A CONSOLIDATING
SYSTEM WITH CONVECTIVE BANDING WRAPPING INTO A RAGGED LOW LEVEL
CIRCULATION CENTER. THE INITIAL INTENSITY IS ASSESSED AT 45 KNOTS
BASED ON A PGTW DVORAK INTENSITY ESTIMATE OF 3.0/3.5 (45/55 KNOTS).
NEAR-RADIAL UPPER LEVEL OUTFLOW, LOW (10-15 KT) VERTICAL WIND SHEAR
(VWS), AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES CONTRIBUTE
TO AN OVERALL FAVORABLE ENVIRONMENT FOR CONTINUED DEVELOPMENT. TS
19W IS TRACKING ALONG THE SOUTHEASTERN PERIPHERY OF A WEAKENING
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHWEST. 500MB ANALYSES
OVER THE PAST TWO DAYS SHOW A RECEDING WESTERN STR (HIGH CENTER JUST
NORTHEAST OF HAINAN ISLAND) WITH A BREAK LOCATED EAST OF TAIWAN.
ADDITIONALLY, THE MAJOR SHORTWAVE TROUGH PREDICTED BY THE MODELS TO
DIG INTO SOUTHEAST CHINA IS IN FACT DIGGING INTO SOUTHEAST CHINA;
THE SHORTWAVE TROUGH IS LOCATED ABOUT 110E WITH COLD AIR ADVECTION
INTO THE NORTHERN PERIPHERY OF THE STR, WHICH WILL SERVE TO FURTHER
WEAKEN THE STEERING STR OVER THE NEXT DAY.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 19W WILL CONTINUE TO TRACK GENERALLY WESTWARD UNDER THE
STEERING INFLUENCE OF THE STR THROUGH TAU 12. HOWEVER, THE SYSTEM IS
EXPECTED TO SLOW AND GRADUALLY TURN WEST-NORTHWESTWARD TO
NORTHWESTWARD AS THE STR WEAKENS AND A COL REGION FORMS NORTH OF THE
SYSTEM. THERE IS SIGNIFICANT UNCERTAINTY IN THIS STAGE OF THE
FORECAST WITH A QUICKLY EVOLVING SYNOPTIC PATTERN AND DYNAMIC
SHORTWAVE TROUGH APPROACHING. THE BULK OF THE NUMERICAL GUIDANCE IS
IN FAIR AGREEMENT WITH SOME DIFFERENCES IN THE TIMING / DURATION OF
THE SHORT-TERM POLEWARD TURN. AFTER TAU 48, THE SHORTWAVE TROUGH IS
FORECAST TO PROPAGATE EASTWARD AND THE STR TO REBUILD, WHICH WILL
ALLOW THE SYSTEM TO RESUME ITS WESTWARD TRACK. TS 19W SHOULD
STEADILY INTENSIFY TO A PEAK OF 60 KTS BY TAU 48 UNDER CONTINUED
FAVORABLE CONDITIONS.
   C. IN THE EXTENDED FORECAST, THE SYSTEM WILL ACCELERATE WESTWARD
AND GRADUALLY WEAKEN AS IT INTERACTS WITH HAINAN ISLAND AND EASTERN
VIETNAM. DUE TO THE COMPLEX STEERING ENVIRONMENT AND DYNAMIC
SYNOPTIC PATTERN, THERE IS MODERATE CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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