Tropical Storm SAUDEL Advisory 10月21日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (SAUDEL) WARNING NR
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 19W (SAUDEL), LOCATED APPROXIMATELY 123 NM
NORTH-NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED SATELLITE IMAGERY
AND RADAR IMAGERY INDICATE THAT TS 19W'S CENTER IS NOW LOCATED OVER
WATER WEST OF BAGUIO AFTER TRACKING ACROSS LUZON; CONVECTIVE
STRUCTURE IS IMPROVING WITH FRAGMENTED BANDING WRAPPING INTO A
RAGGED LOW LEVEL CIRCULATION CENTER (LLCC). A 201753Z AMSR2 89GHZ
MICROWAVE IMAGE REVEALS A PARTIALLY EXPOSED, BROAD LLCC WITH
FRAGMENTED OUTER BANDING AND DISORGANIZED CENTRAL CONVECTION. THE
INITIAL INTENSITY HAS DECREASED SLIGHTLY TO 40 KNOTS BASED ON DVORAK
INTENSITY ESTIMATES RANGING FROM T2.5 TO T3.0 (35-45 KNOTS). NEAR-
RADIAL UPPER LEVEL OUTFLOW, LOW (10-15 KT) VERTICAL WIND SHEAR
(VWS), AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST)
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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