WDPN31 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W (KROVANH) 
WARNING NR 005//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 26W (KROVANH), LOCATED APPROXIMATELY
414 NM EAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WEST-
SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
MULTISPECTRAL SATELLITE IMAGERY DEPICTS A BROAD LOW-LEVEL 
CIRCULATION (LLC) WITH MULTIPLE VORTICES ROTATING CYCLONICALLY 
AROUND THE LLC. BASED ON A 202316Z SSMIS 91GHZ COMPOSITE IMAGE, THE 
CENTER IS ILL-DEFINED, HOWEVER, THE CONVECTIVE BANDING OVER THE 
NORTHEAST QUADRANT OF THE SYSTEM HAS IMPROVED SLIGHTLY BUT REMAINS 
FRAGMENTED. CONSEQUENTLY, THERE IS LOW CONFIDENCE IN THE INITIAL 
POSITION. THE INITIAL INTENSITY REMAINS ASSESSED AT 30 KNOTS BASED 
ON THE OVERALL WEAK CONVECTIVE STRUCTURE, AND T1.0-1.5 (25 KNOTS) 
DVORAK SUBJECTIVE ESTIMATES AND A 210040Z ADT OBJECTIVE ESTIMATE OF 
2.4 (34 KNOTS). UPPER-LEVEL ANALYSIS REVEALS A MARGINAL ENVIRONMENT 
WITH HIGH (25 KNOTS) VERTICAL WIND SHEAR OFFSET BY STRONG POLEWARD 
OUTFLOW. SST VALUES (28-29C) REMAIN CONDUCIVE. THE SYSTEM IS 
TRACKING SLOWLY WEST-SOUTHWESTWARD ALONG THE SOUTHEAST PERIPHERY OF 
A LOW-LEVEL SUBTROPICAL RIDGE POSITIONED TO THE NORTHWEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TD 26W IS EXPECTED TO TRACK WEST-SOUTHWESTWARD TO WESTWARD 
ALONG THE SOUTHERN FLANK OF THE LOW-LEVEL STR THROUGH TAU 48. THE 
SYSTEM IS FORECAST TO INTENSIFY SLIGHTLY OVER THE NEXT 12 HOURS 
AS VWS DECREASES SLIGHTLY WITH PERSISTENT POLEWARD OUTFLOW. AFTER 
TAU 12, TD 26W SHOULD WEAKEN STEADILY AS IT TRACKS AWAY FROM THE 
STRONG SURGE FLOW AND UPPER-LEVEL DIVERGENCE DECREASES. THE SYSTEM 
IS FORECAST TO DISSIPATE SOUTH OF VIETNAM BY TAU 48. EXCLUDING THE 
ECMWF TRACKER, WHICH LOSES THE CIRCULATION AFTER TAU 36 AND JUMPS 
NORTHWESTWARD ERRONEOUSLY, THE BULK OF NUMERICAL MODEL GUIDANCE 
SUPPORTS THE JTWC FORECAST TRACK, HOWEVER, THERE IS LOW OVERALL 
CONFIDENCE IN THE TRACK DUE TO HIGH UNCERTAINTY IN THE INITIAL 
POSITION.//
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