Tropical Storm SAUDEL Advisory Wed Oct 21

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (SAUDEL) WARNING NR
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 19W (SAUDEL), LOCATED APPROXIMATELY 149 NM
EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 17
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE
IMAGERY DEPICTS A PARTIALLY-EXPOSED SYSTEM WITH BROAD CONVECTIVE
BANDING WRAPPING INTO A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER
(LLCC) FROM THE NORTH. A 200737Z SSMI 85 GHZ MICROWAVE IMAGE SHOWS
DEEP CONVECTION OVER THE WESTERN SEMI-CIRCLE WITH FRAGMENTED BANDING
WRAPPING INTO A DEFINED LLCC. THE INITIAL INTENSITY IS ASSESSED AT
40
KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF T2.5-3.0 (35-45 KTS)
FROM
PGTW AND RJTD. 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 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. TS 19W WILL CONTINUE TRACKING GENERALLY WESTWARD UNDER THE
STEERING INFLUENCE OF THE STR THROUGH TAU 72. HOWEVER, THE SYSTEM IS
EXPECTED TO SLOW FROM TAU 36 TO TAU 72 AS THE STR TEMPORARILY
WEAKENS
DUE TO THE APPROACH OF A MIDLATITUDE SHORTWAVE TROUGH WHICH IS
EXPECTED TO DIG OVER SOUTHEAST CHINA. DURING THIS TIME, MODEL
GUIDANCE
AND THE 19/00Z ECMWF ENSEMBLE INDICATE A SHORT-TERM NORTH-
NORTHWESTWARD TO NORTHWESTWARD TRACK DUE TO THE LACK OF STEERING
GUIDANCE. THE NAVGEM AND ECMWF MODEL SOLUTIONS PRESENT THE MOST
AGGRESSIVE NORTH-NORTHWESTWARD TRACK SOLUTIONS AT THIS TIME,
TRACKING
TS 19W FURTHER NORTH THAN THE CURRENT JTWC TRACK FORECAST. THE JTWC
TRACK FORECAST LIES NEAR THE MULTI-MODEL CONSENSUS. THE SYSTEM IS
EXPECTED TO MAINTAIN ITS INTENSITY AS IT MAKES LANDFALL IN LUZON
NEAR
TAU 6 THEN INTENSIFY AS IT REEMERGES OVER THE SOUTH CHINA SEA NEAR
TAU
12-18. AFTERWARDS, TS 19W SHOULD STEADILY INTENSIFY TO A PEAK OF 60
KTS BY TAU 72 UNDER FAVORABLE CONDITIONS.
   C. AS THE AFOREMENTIONED SHORTWAVE TROUGH PROPAGATES EASTWARD,
THE
STR WILL REBUILD TO THE NORTH, ALLOWING TS 19W TO ACCELERATE
WESTWARD
ALONG ITS SOUTHERN PERIPHERY. ALONG THIS TRACK, THE SYSTEM WILL
MAINTAIN INTENSITY UNTIL IT BEGINS TO INTERACT WITH HAINAN ISLAND
AND
BEGINS TO WEAKEN SLIGHTLY. DUE TO THE COMPLEX STEERING ENVIRONMENT
AND
DYNAMIC SYNOPTIC PATTERN, THERE IS MODERATE CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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