Tropical Storm SAUDEL Advisory 10月20日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (NINETEEN)
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 19W (NINETEEN), LOCATED APPROXIMATELY
297 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD
AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS A SLOWLY CONSOLIDATING SYSTEM WITH BROAD
CONVECTIVE BANDING WRAPPING INTO A RAGGED LOW-LEVEL CIRCULATION
CENTER (LLCC). A 191710Z AMSR2 89GHZ COLOR COMPOSITE MICROWAVE IMAGE
INDICATES SHALLOW BANDING WRAPPING INTO AN EXPOSED, DEFINED LLCC
WITH MULTIPLE FRAGMENTED BANDS OVER THE NORTHERN AND WESTERN
SEMICIRCLES. THIS MICROWAVE IMAGE SUPPORTS THE INITIAL POSITION WITH
GOOD CONFIDENCE. THE INITIAL INTENSITY REMAINS ASSESSED AT 30 KNOTS
BASED ON DVORAK INTENSITY ESTIMATES OF T2.0 (30 KNOTS) FROM PGTW AND
RJTD. UPPER-LEVEL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT WITH NEAR-
RADIAL OUTFLOW AND LOW VERTICAL WIND SHEAR. SST VALUES (29-30C)
REMAIN CONDUCIVE. TD 19W IS TRACKING WEST-NORTHWESTWARD ALONG THE
SOUTHWEST PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTHEAST WITH AN EXTENSION OF THE STR TO THE
NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 19W WILL CONTINUE TRACKING WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE STR THROUGH TAU 72, HOWEVER, THE SYSTEM IS
EXPECTED TO SLOW FROM TAU 48 TO TAU 72 AS THE STR WEAKENS
TEMPORARILY. THIS WEAKENING OF THE STR IS DUE TO AN APPROACHING
BROAD MIDLATITUDE SHORTWAVE TROUGH, WHICH IS FORECAST TO DIG OVER
SOUTHEAST CHINA. NUMERICAL MODEL GUIDANCE AND THE 19/12Z ECMWF
ENSEMBLE INDICATE POTENTIAL FOR THIS SLOW-DOWN WITH A POSSIBLE SHORT-
TERM NORTH-NORTHWESTWARD TO NORTHWESTWARD TURN. TD 19W IS FORECAST
TO INTENSIFY TO TROPICAL STORM STRENGTH PRIOR TO MAKING LANDFALL
ALONG THE EAST COAST OF LUZON NEAR TAU 18 AND WILL INTENSIFY AS IT
REEMERGES OVER THE SOUTH CHINA SEA AFTER TAU 24. THE SYSTEM IS
EXPECTED TO INTENSIFY MORE SIGNIFICANTLY AFTER TAU 24 TO AN
INTENSITY OF 55 KNOTS BY TAU 72 UNDER FAVORABLE CONDITIONS.
   C. IN THE EXTENDED PERIOD, THE AFOREMENTIONED SHORTWAVE TROUGH
WILL PROPAGATE EASTWARD ALLOWING THE STR TO REBUILD TO THE NORTH.
CONSEQUENTLY, TD 19W WILL ACCELERATE WESTWARD THROUGH TAU 120 WHILE
INTENSIFYING TO A PEAK INTENSITY OF 60 KNOTS BY TAU 96. SLIGHT
WEAKENING IS ANTICIPATED NEAR TAU 120 AS THE SYSTEM BEGINS TO
INTERACT WITH HAINAN ISLAND. DUE TO THE COMPLEX, EVOLVING SYNOPTIC
PATTERN, THERE IS MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK.//
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