WDPN34 PGTW 161500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (RUMBIA) WARNING NR 
07//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 21W (RUMBIA), LOCATED APPROXIMATELY 103 NM EAST-
SOUTHEAST OF SHANGHAI, CHINA, HAS TRACKED WEST-NORTHWESTWARD AT
07 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON 
RECENT INFRARED SATELLITE IMAGERY FIX FROM PGTW AND A LOW-LEVEL 
CIRCULATION CENTER FEATURE EVIDENT IN 160930Z SSMIS MICROWAVE 
SATELLITE IMAGERY. THE INTENSITY OF 40 KNOTS IS BASED ON 30-35 KNOT 
SUBJECTIVE DVORAK INTENSITY ESTIMATES, 35-40 KNOT WINDS EVIDENT IN 
EARLIER ASCAT DATA, STRUCTURE EVIDENT IN SATELLITE IMAGERY AND A 
160930Z AUTOMATED SATELLITE INTENSITY CONSENSUS ESTIMATE OF 46 
KNOTS. TS 21W HAS CONTINUED TO CONSOLIDATE OVER THE PAST SIX HOURS, 
WITH A NEW FLARE OF DEEP CONVECTION EVIDENT NEAR THE CIRCULATION 
CENTER. IMPROVED ORGANIZATION HAS BEEN SUPPORTED BY DEVELOPMENT OF 
RIDGING ALOFT AND FORMATION OF A POLEWARD OUTFLOW CHANNEL. THE 
STRONGEST WINDS AND PRIMARY CONVECTIVE BANDING REMAIN SITUATED ALONG 
THE EASTERN PORTION OF THE BROAD CIRCULATION. TS 21W IS TRACKING 
WEST-NORTHWESTWARD UNDER THE INFLUENCE OF A DEEP-LAYER STEERING 
RIDGE 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 WILL CONTINUE TRACKING WEST-NORTHWESTWARD UNDER THE 
INFLUENCE OF THE STEERING RIDGE TO THE NORTH THROUGHOUT THE FORECAST 
PERIOD. THE SYSTEM IS EXPECTED TO MAKE LANDFALL JUST SOUTH OF 
SHANGHAI WITHIN THE NEXT 12 HOURS AND DISSIPATE INLAND BY TAU 36. 
ADDITIONAL INTENSIFICATION IS POSSIBLE PRIOR TO LANDFALL, BUT WILL 
BE LIMITED BY DECREASING ALONG-TRACK SEA SURFACE TEMPERATURES AND 
INITIAL LAND INTERACTION. NUMERICAL MODELS REMAIN IN GOOD AGREEMENT, 
RESULTING IN HIGH CONFIDENCE IN THE TRACK FORECAST.//
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