WDPN31 PGTW 211500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W (KROVANH) 
WARNING NR 007//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 26W (KROVANH), LOCATED APPROXIMATELY 339 
NM EAST-SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED 
INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FAIRLY BROAD BUT 
DISORGANIZED LOW-LEVEL CIRCULATION (LLC) WITH MULTIPLE VORTICES 
ROTATING CYCLONICALLY AROUND THE LLC, PARTICULARLY IN THE SOUTH AND 
SOUTHEAST QUADRANTS, WITH FLARING CONVECTION NEAR THE ASSESSED 
CENTER. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED 
ON A 211238Z ASCAT-A BULLSEYE, WHICH CONFIRMED THE ELONGATED NATURE 
OF THE CIRCULATION, AND THE MULTIPLE VORTICES. THE INITIAL INTENSITY 
IS ASSESSED WITH FAIR CONFIDENCE AND IS HEDGED HIGHER THAN THE PGTW 
T1.0 (25 KTS) SUBJECTIVE DVORAK INTENSITY ESTIMATE BUT SLIGHTLY 
LOWER THAN AN ADT ESTIMATE OF T2.3 (33 KNOTS) BASED ON THE 
AFOREMENTIONED SCATTEROMETER DATA. THE ASCAT PASS INDICATED THAT THE 
WIND FIELD ASSOCIATED WITH THE NORTHEAST SURGE EVENT REMAINS WELL 
ESTABLISHED, WITH 35 KNOT WINDS EXTENDING SOUTH ALONG THE COAST OF 
VIETNAM TO ROUGHLY 10 DEGREES NORTH, AND 25-30 KNOT WINDS EXTENDING 
FURTHER OFFSHORE AND STARTING TO WRAP AROUND THE LLC FROM THE NORTH 
TO SOUTHWEST QUADRANTS. THE OVERALL ENVIRONMENT REMAINS MARGINAL, 
WITH MODERATE TO HIGH (20-25 KTS) VWS BEING OFFSET BY STRONG, 
DIVERGENT, POLEWARD OUTFLOW AND WARM (28-29C) SSTS. THE SYSTEM IS 
TRACKING SLOWLY WEST-SOUTHWESTWARD ALONG THE SOUTHEAST PERIPHERY OF 
A LOW-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHWEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TD 26W IS FORECAST TO CONTINUE TRACKING WEST-SOUTHWEST THROUGH 
TAU 12, THEN WEST THROUGH THE REMAINDER OF THE FORECAST, ALONG THE 
SOUTHERN PERIPHERY OF THE LOW-LEVEL STR TO THE NORTH. VWS HAS 
SLACKENED SLIGHTLY OVER THE PAST FEW HOURS, NOW ROUGHLY 20 KNOTS 
FROM THE EAST, AND IS FORECAST TO CONTINUE TO SLACKEN THROUGH TAU 
24. HOWEVER, UPPER-LEVEL OUTFLOW IS EXPECTED TO WEAKEN AT THE SAME 
TIME, SERVING TO OFFSET THE DECREASED WIND SHEAR. THE COMPETING AND 
OFFSETTING FACTORS WILL ULTIMATELY LEAD TO A PERIOD OF STEADY 
INTENSITY THROUGH TAU 24. VWS IS FORECAST TO INCREASE AGAIN AFTER 
TAU 24, AND COMBINED WITH CONVERGENCE UPPER-LEVEL FLOW, WILL 
STEADILY WEAKEN THE SYSTEM, LEADING TO DISSIPATION OVER WATER SOUTH 
OF VIETNAM BY TAU 48. NUMERICAL MODEL GUIDANCE GENERALLY AGREES WITH 
THE OVERALL SCENARIO, AND WITH THE EXCEPTION OF THE NAVGEM SOLUTION, 
SUPPORTS THE JTWC FORECAST WITH OVERALL FAIR CONFIDENCE.//
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