WDPN31 PGTW 130300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W WARNING NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 26W, LOCATED APPROXIMATELY 325 NM 
EAST-SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS.  THE POSITION HAS 
BEEN ADJUSTED SLIGHTLY SOUTHWARD FROM THE PREVIOUS WARNING BASED ON 
NEW ANIMATED MULTISPECTRAL SATELLITE IMAGERY. THE CURRENT INTENSITY 
IS BASED ON DVORAK CI VALUES OF 1.5 FROM PGTW AND RJTD AND LOCAL 
SURFACE PRESSURE OBSERVATIONS SHOWING ABOUT 1004 MB, WHICH ROUGHLY 
EQUATES TO A 25 KNOT SYSTEM THROUGH TROPICAL CYCLONE WIND PRESSURE 
RELATIONSHIPS. THE LOW-LEVEL CIRCULATION CENTER HAS TURNED TO THE 
WEST-SOUTHWEST UNDER THE INFLUENCE OF LOW-LEVEL, EAST-NORTHEASTERLY 
FLOW ASSOCIATED WITH A COLD SURGE ANALYZED ACROSS THE WESTERN 
PORTION OF THE SOUTH CHINA SEA. INCREASING INTERACTION WITH THE DRY, 
COOL AIR ASSOCIATED WITH THE SURGE AND PERSISTENT EASTERLY VERTICAL 
WIND SHEAR HAVE BEEN DETRIMENTAL TO THE OVERALL STRUCTURE OF TD 26W. 
3. FORECAST REASONING.
   A. THE FORECAST PHILOSOPHY FOR TD 26W REMAINS UNCHANGED FROM THE 
LAST PROGNOSTIC REASONING.
   B. TD 26W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A LOW-LEVEL 
SUBTROPICAL RIDGE AND HAS STARTED TO TURN MORE WEST-SOUTHWESTWARD AS 
IT HAS COME UNDER GREATER INFLUENCE OF STRONG NORTHEASTERLY FLOW 
ALONG THE COAST OF VIETNAM. PERSISTENT VERTICAL WIND SHEAR WILL 
CONTINUE TO HAMPER DEVELOPMENT OF TD 26W. MODEL GUIDANCE IS IN 
INCREASING AGREEMENT REGARDING TRACK AND INTENSITY, INDICATING A 
WEST-SOUTHWESTWARD TURN AND DISSIPATION BELOW THE 25 KNOT WARNING 
THRESHOLD WITHIN THE NEXT 24 HOURS.//
NNNN