WDPN31 PGTW 211500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (SAUDEL) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS. 
   TROPICAL STORM (TS) 19W (SAUDEL), LOCATED APPROXIMATELY 217 NM 
WEST-NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
SOUTHWESTWARD AT 10 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED 
ENHANCED INFRARED SATELLITE IMAGERY SHOWS PERSISTENT DEEP CONVECTION 
OVERHEAD THE LOW LEVEL CIRCULATION CENTER (LLCC) WITH CONVECTIVE 
BANDING WRAPPING INTO THE CENTER. A 211033Z SSMIS 91 GHZ MICROWAVE 
IMAGERY DEPICTS A WELL-DEFINED LLCC WITH THE MAJORITY OF THE 
ASSOCIATED DEEP CONVECTION LOCATED OVER THE WESTERN SEMICIRCLE WHILE 
THE 211033Z SSMIS 37 GHZ MICROWAVE IMAGE REVEALS A TIGHTENING 
MICROWAVE EYE FEATURE. BOTH IMAGES SUPPORT THE INITIAL POSITION WITH 
HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AS 50 KTS BASED 
ON PGTW/RJTD/KNES DVORAK CURRENT INTENSITY ESTIMATES OF T3.0-3.5 (45-
55 KTS) AND A 211306Z ASCAT-B IMAGE REVEALING A SWATH OF 45-49 KT 
WINDS LOCATED TO THE SOUTHWEST. OVERALL, THE ENVIRONMENT SURROUNDING 
TS 19W IS FAVORABLE FOR CONTINUED DEVELOPMENT DUE TO LOW (10-15 KTS) 
VERTICAL WIND SHEAR (VWS), WARM (29-30 CELSIUS) SEA SURFACE 
TEMPERATURES (SST), AND NEAR-RADIAL UPPER-LEVEL OUTFLOW. A SHORTWAVE 
TROUGH CURRENTLY DIGGING OVER SOUTHEAST CHINA HAS BEGUN TO WEAKEN 
THE STEERING SUBTROPICAL RIDGE (STR), THUS TS 19W IS ENTERING A 
WEAKENED STEERING ENVIRONMENT WITH A COL FORMING TO THE NORTH. 
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR TERM, THE SYSTEM WILL BEGIN TO SLOWLY TURN TO A 
WEST-NORTHWESTWARD THEN NORTHWESTWARD TRACK AS THE SHORTWAVE TROUGH 
FURTHER WEAKENS THE STR AND THE AFOREMENTIONED COL FORMS NORTH OF 
THE SYSTEM. THERE IS SOME UNCERTAINTY DURING THIS PORTION OF THE 
FORECAST DUE TO VARIATIONS IN THE TIMING OF THE SHORTWAVE TROUGH 
APPROACH. THE MAJORITY OF THE NUMERICAL MODEL GUIDANCE IS IN FAIR 
AGREEMENT WITH SOME DIFFERENCES REGARDING THE TIMING AND DURATION OF 
THE POLEWARD TURN. AFTER TAU 36, THE SHORTWAVE TROUGH IS EXPECTED TO 
PROPAGATE EASTWARD WHICH WILL CAUSE THE STR TO REBUILD AND TS 19W TO 
RESUME ITS WESTWARD TRACK ALONG THE SOUTHERN PERIPHERY OF THE STR. 
CONTINUED FAVORABLE ENVIRONMENTAL CONDITIONS INDICATE TS 19W SHOULD 
INTENSIFY TO A PEAK OF 60 KTS BY TAU 36. THE SYSTEM SHOULD MAINTAIN 
THIS INTENSITY UNTIL IT BEGINS TO INTERACT WITH HAINAN ISLAND WHICH 
WILL CAUSE THE SYSTEM TO WEAKEN SLIGHTLY BY TAU 72.
   C. IN THE EXTENDED FORECAST, TS 19W WILL CONTINUE TO STEADILY 
WEAKEN AS IT TRACKS WESTWARD UNDER THE STEERING INFLUENCE OF THE 
STR. LANDFALL IS EXPECTED BY TAU 96 AND THEN THE SYSTEM WILL WEAKEN 
AS IT TRAVERSES THE RUGGED TERRAIN OF VIETNAM. OVERALL, THERE IS 
MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK DUE TO THE COMPLEX 
STEERING ENVIRONMENT AND DYNAMIC SYNOPTIC PATTERN.//
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