WDPN32 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (MAWAR) 
WARNING NR 04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 18W (MAWAR), LOCATED APPROXIMATELY 244 NM EAST-
SOUTHEAST OF HONG KONG, HAS TRACKED NORTH-NORTHWESTWARD AT 04
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE 
IMAGERY SHOWS A FLARING CONVECTION ASSOCIATED WITH A BROAD, BUT 
SLOWLY CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC). A 011008Z 
SSMIS 91GHZ  MICROWAVE IMAGE SHOWS DEEP CONVECTION IN THE WESTERN 
SEMI-CIRCLE WITH WEAK CONVECTIVE BANDING WRAPPING INTO THE LLCC. THE 
CURRENT POSITION IS PLACED WITH LOW CONFIDENCE BASED ON THE 
DISORGANIZED STATUS OF THE SYSTEM AND VARIATIONS IN RECENT SATELLITE 
FIX LOCATIONS FROM MULTIPLE AGENCIES. THE INITIAL INTENSITY 
ASSESSMENT OF 35 KNOTS IS BASED ON THE UPPER END OF MULTIAGENCY 
DVORAK ESTIMATES RANGING FROM T2.0 TO T2.5 (30-35 KNOTS) FROM BOTH 
PGTW AND RJTD RESPECTIVELY. ENVIRONMENTAL ANALYSIS REVEALS THAT THE 
SYSTEM HAS STRONG POLEWARD AND EQUATORWARD OUTFLOW, IS IN AN AREA OF 
LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS), AND IS TRACKING THROUGH 
WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES. TS MAWAR IS CURRENTLY 
TRACKING SLOWLY NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF AN 
EXTENSION OF THE SUBTROPICAL RIDGE (STR) BUILDING IN THE PHILIPPINE 
SEA.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST TRACK PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.   
   B. TS 18W IS FORECAST TO TRACK NORTH-NORTHWESTWARD FOR THE NEXT 
72 HOURS. THE STEERING STR WILL CONTINUE TO BUILD AND TRANSITS 
NORTHWESTWARD TOWARDS TAIWAN REMAINING THE PRIMARY STEERING FEATURE 
FOR TS MAWAR. LOW VWS, WARM SSTS AND GOOD OUTFLOW WILL PERSIST UNTIL 
THE SYSTEM MAKES LANDFALL ALLOWING FOR A GRADUAL INTENSIFICATION 
WITH A PEAK OF 50 KNOTS. TS 18W WILL MAKE LANDFALL EAST OF HONG KONG 
AFTER TAU 36. ONCE OVER LAND, THE RUGGED TERRAIN OF SOUTHEASTERN 
CHINA WILL RAPIDLY WEAKEN THE SYSTEM, WITH COMPLETE DISSIPATION 
OCCURRING BY TAU 72. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT 
LENDING HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.//
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