WDPN31 PGTW 030300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (KROSA) WARNING NR 21// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 29W (KROSA), LOCATED APPROXIMATELY 128 NM SOUTH-SOUTHEAST OF HONG KONG, HAS TRACKED SOUTHWARD AT 01 KNOT OVER THE PAST SIX HOURS. THE SYSTEM IS QUASI-STATIONARY AND APPEARS TO BE MAKING A TIGHT LOOPING MOTION BASED ON ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A SERIES OF CLOSELY-SPACED POSITION FIXES FROM VARIOUS AGENCIES. THE CENTRAL CONVECTION HAS REMAINED VIRTUALLY UNCHANGED AS THE SYSTEM IS TRAPPED IN A COL ZONE AT THE WESTERN EDGE OF THE STEERING SUBTROPICAL RIDGE (STR). THE CYCLONE IS IN AN AREA OF WEAK TO MODERATE (10-20 KNOT) VERTICAL WIND SHEAR (VWS); HOWEVER, ANIMATED WATER VAPOR IMAGERY DEPICTS RADIAL OUTFLOW WITH A STRONG POLEWARD COMPONENT, WHICH CONTINUES TO FUEL THE REMNANT DEEP CONVECTION. THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION BASED ON THE MSI ANIMATION. THE INITIAL INTENSITY OF 80 KNOTS IS AVERAGED FROM DVORAK INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. AN EXTENSION OF THE STR BUILDING-IN FROM THE INDOCHINA PENINSULA IS EXPECTED TO ASSUME STEERING AND DEFLECT TYPHOON KROSA TO A SOUTHWESTWARD TRAJECTORY OVER THE NEXT 12-24 HOURS. BY TAU 72, THE SYSTEM WILL HAVE MADE LANDFALL AND DISSIPATED OVER SOUTH VIETNAM, SOUTH OF HUE. THE STEADY WEAKENING PRIOR TO LANDFALL WILL BE CAUSED BY INCREASING VWS AND THE INFLUX OF COOLER CONTINENTAL DRY AIR FROM CHINA. NUMERIC MODEL GUIDANCE REMAINS IN GENERALLY TIGHT AGREEMENT, HOWEVER, GIVEN THE UNCERTAINTY ASSOCIATED WITH CYCLONES IN A QUASI-STATIONARY STATE, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST. // NNNN