WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (ETAU) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 24W (ETAU), LOCATED APPROXIMATELY 350 NM
EAST-SOUTHEAST OF DA NANG, VIETNAM, HAS TRACKED WESTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH CONVECTIVE BANDING OVER 
THE WESTERN SEMICIRCLE WRAPPING INTO THE SOUTHWEST QUADRANT OF A 
DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). A 082029Z SSMIS 91GHZ 
COMPOSITE IMAGE REVEALS SHALLOW BANDING OVER THE EASTERN SEMICIRCLE 
WRAPPING INTO THE LLCC, WHICH SUPPORTS THE INITIAL POSITION WITH 
FAIR CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 35 KTS BASED 
ON PGTW/RJTD DVORAK INTENSITY ESTIMATES OF T2.5 (35 KNOTS). UPPER-
LEVEL ANALYSIS INDICATES A GENERALLY FAVORABLE ENVIRONMENT WITH LOW 
(10 KNOTS) EASTERLY VERTICAL WIND SHEAR AND ENHANCED POLEWARD 
OUTFLOW. SST VALUES REMAIN CONDUCIVE AT 27-28C. TS 24W IS TRACKING 
ALONG THE SOUTHERN PERIPHERY OF A LOW- TO MID-LEVEL SUBTROPICAL 
RIDGE (STR) ENTRENCHED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 24W IS EXPECTED TO TRACK QUICKLY WESTWARD UNDER THE 
STEERING INFLUENCE OF THE AFOREMENTIONED STR THROUGH THE FORECAST 
PERIOD, MAKING LANDFALL OVER EASTERN VIETNAM NEAR TAU 24. AFTER TAU 
24, THE SYSTEM WILL TRACK INLAND AND DISSIPATE OVER MOUNTAINOUS 
TERRAIN BY TAU 48. NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT 
WITH A SPREAD OF 53NM AT LANDFALL LENDING HIGH CONFIDENCE IN THE 
JTWC FORECAST TRACK. THE 08/1200Z ECMWF ENSEMBLE INDICATES GREATER 
SPREAD AND UNCERTAINTY AT LANDFALL WITH A 90NM SPREAD IN SOLUTIONS 
(LANDFALL CENTER LOCATION FROM 12.5N TO 14.0N).//
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