WDPN32 PGTW 160300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (RUMBIA) WARNING NR 05// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 21W (RUMBIA), LOCATED APPROXIMATELY 262 NM NORTHWEST OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS FRAGMENTED BANDED WRAPPING INTO A BROAD AND PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). A 152306Z GPM MICROWAVE PASS REVEALS HEAVY CONVECTION ALONG THE OUTER PERIPHERY OF 21W SURROUNDING A NEARLY CALM CENTER, TYPICAL OF A MONSOON DEPRESSION STRUCTURE. THE INITIAL POSITION IS BASED ON FIXES FROM PGTW AND RJTD, AND SUPPORTED BY THE 36GHZ COLOR COMPOSITE FROM THE AFOREMENTIONED GMI DATA. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON A RANGE OF DVORAK CURRENT INTENSITY ESTIMATES FROM T2.0 TO T2.5. THE LLCC HAS BEEN VERY SLOW TO CONSOLIDATE DESPITE LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS) OVER HEAD AND MODERATELY FAVORABLE OUTFLOW CONDITIONS. TRACK MOTION HAS BEEN STEADILY NORTHWESTWARD OVER THE PAST SIX HOURS, UNDER THE STEERING INFLUENCE OF A LOW TO MID-LEVEL STEERING RIDGE BUILDING TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS RUMBIA IS EXPECTED TO CONTINUE ITS NORTHWESTWARD MOTION AND MAKE LANDFALL NEAR SHANGHAI, CHINA AFTER TAU 12. ALTHOUGH THE FORECAST PEAK OF 40 KNOTS TAKES INTO ACCOUNT THAT SLIGHT CONSOLIDATION OF THE LLCC MAY OCCUR GIVEN THE FAVORABLE UPPER LEVEL SUPPORT, THERE IS LIMITED POTENTIAL FOR FURTHER INTENSIFICATION DUE TO DECLINING SSTS ALONG THE PATH OF MOTION. NUMERICAL MODELS ARE IN GOOD AGREEMENT, AND THERE IS HIGH CONFIDENCE IN THE JTWC OFFICIAL FORECAST.// NNNN