WDPN32 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (THIRTY) WARNING NR 
10//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 30W (THIRTY), LOCATED APPROXIMATELY 507 NM EAST OF 
HO CHI MINH CITY, VIETNAM, HAS TRACKED WESTWARD AT 16 KNOTS OVER THE 
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) 
DEPICTS A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH 
THE BULK OF THE DEEP CONVECTION LOCATED TO THE NORTH OF THE LLCC. 
THE EIR INDICATES SUBTLE IMPROVEMENTS IN THE CURVATURE OF THE 
CONVECTIVE BANDING, WHICH IS ALSO EVIDENT IN A 051025Z CORIOLIS 
IMAGE THAT REVEALS CURVED BANDS ALONG THE WESTERN FLANK. THE INITIAL 
POSITION IS BASED ON THE EIR ANIMATION AND EXTRAPOLATED FROM THE 
CORIOLIS IMAGE WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS 
ASSESSED AT 35 KNOTS BASED ON THE SLOWLY CONSOLIDATING STRUCTURE AS 
WELL AS DVORAK INTENSITY ESTIMATES FROM PGTW AND KNES. UPPER LEVEL 
ANALYSIS INDICATES A GENERALLY FAVORABLE ENVIRONMENT WITH WEAK (05 
TO 10 KNOT) VERTICAL WIND SHEAR AND GOOD POLEWARD OUTFLOW. TD 30W IS 
CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF THE DEEP-LAYERED 
SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 30W IS EXPECTED TO MAINTAIN A WESTWARD TO WEST-
NORTHWESTWARD TRACK ALONG THE SOUTHERN EDGE OF THE STR THROUGH THE 
FORECAST PERIOD. TS 30W WILL CONTINUE TO INTENSIFY OVER THE SOUTH 
CHINA SEA WHERE MARGINALLY FAVORABLE UPPER LEVEL CONDITIONS, IN 
ADDITION TO PERENNIALLY WARM WATERS ALONG THE TRACK, WILL FUEL 
MODEST INTENSIFICATION, PEAKING AT 55 KNOTS BY TAU 24. SHORTLY AFTER 
TAU 24, THE SYSTEM WILL MAKE LANDFALL AGAIN, THIS TIME OVER SOUTHERN 
VIETNAM, NEAR THE CITY OF NHA TRANG. TS 30W WILL BEGIN TO ERODE AS 
IT DRAGS ACROSS VIETNAM AND SOUTHERN CAMBODIA THROUGH TAU 48. PRIOR 
TO TAU 72, THE SYSTEM WILL BRIEFLY DRIFT ACROSS THE NORTHERN PORTION 
OF THE GULF OF THAILAND AND CROSS THE MALAY PENINSULA INTO THE 
ANDAMAN SEA, MAINTAINING AN INTENSITY OF 30 KNOTS.
   C. AFTER TAU 72, TS 30W TRACK INTO THE BAY OF BENGAL AS A WEAK TD 
AND BEGIN TO SLOWLY INTENSIFY TO 35 KTS BY TAU 120. THIS IS 
CONSISTENT WITH THE LATEST DYNAMIC MODEL FIELDS, WHICH ARE BEGINNING 
TO INDICATE MODEST REDEVELOPMENT OF THE SYSTEM IN THE BAY OF BENGAL 
AFTER TAU 96. WITH THE EXCEPTION OF JENI AND JGSM, THE JTWC MULTI-
MODEL CONSENSUS MEMBERS SHOW FAIRLY TIGHT AGREEMENT THROUGHOUT THE 
FORECAST TRACK. THE JTWC FORECAST TRACK IS LAID CLOSE TO THE MULTI-
MODEL CONSENSUS AND IS CONSISTENT WITH THE PREVIOUS WARNING. THERE 
IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK BASED ON THE TIGHT 
AGREEMENT IN THE DYNAMIC AND ENSEMBLE GUIDANCE; HOWEVER, UNCERTAINTY 
REMAINS FAIRLY HIGH WITH RESPECT TO THE REDEVELOPMENT SCENARIO AFTER 
TAU 72.//
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