WDPN31 PGTW 100300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (TALIM) WARNING 
NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 20W (TALIM), LOCATED APPROXIMATELY 302 NM WEST-
NORTHWEST OF NAVAL STATION GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 
11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY SHOWS EXPOSED LOW LEVEL FLOW, WITH CLOUD LINES IN THE 
NORTHERN PORTION OF THE CIRCULATION FLOWING SOUTHWARDS INTO THE 
STILL OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC).  DEEP 
CONVECTION HAS BECOME MORE SYMMETRICAL OVER THE PAST SIX HOURS, 
THOUGH IT IS CURRENTLY MOSTLY CONFINED TO THE SOUTH OF THE LLCC. A 
092102Z SSMIS 89GHZ MICROWAVE  IMAGE CONFIRMS THE  WELL DEFINED LOW 
LEVEL BANDING INTO THE LLCC , WITH MOST CONVECTION ALONG THE 
WESTERN TO SOUTHERN PERIPHERY, THOUGH SOME NASCENT CONVECTION WAS 
REFORMING OVER THE LLCC AT THIS TIME. THE INITIAL POSITION IS 
PLACED WITH MODERATE CONFIDENCE BASED ON THE PREVIOUSLY MENTIONED 
MICROWAVE IMAGERY, ANALYSIS OF THE LOW LEVEL CLOUD LINES AND 
AUTOMATED DVORAK TECHNIQUE (ADT) FIX POSITIONS OVER THE PREVIOUS 
SIX HOURS.  THE INITIAL INTENSITY REMAINS AT 40 KNOTS BASED ON 
DVORAK INTENSITY ESTIMATES OF T2.5 (35 KNOTS) FROM PGTW, OBJECTIVE 
INTENSITY ESTIMATES OF T3.0 (45 KNOTS) AND THE SHEARED APPEARANCE 
OF THE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES THE SYSTEM IS IN A 
SOMEWHAT MARGINAL AREA.  VERTICAL WIND SHEAR HAS INCREASED TO THE 
MODERATE RANGE (15-20 KNOTS) FROM THE NORTH, APPLYING SOME PRESSURE 
AND LIMITING THE OPPORTUNITY FOR CONSOLIDATION. OUTFLOW REMAINS 
MARGINAL, WITH A SINGLE EQUATORWARD CHANNEL. TS 20W IS TRACKING 
WEST-NORTHWEST WARD UNDER THE INFLUENCE OF AN EXTENSION OF A DEEP-
LAYER SUB-TROPICAL RIDGE (STR) CENTERED NEAR OKINAWA. 
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY 
FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS TALIM WILL CONTINUE TRACKING WEST-NORTHWEST IN THE 
PHILIPPINE SEA THROUGH TAU72 UNDER THE STEERING INFLUENCE OF THE 
EXTENSION OF THE DEEP STR WHICH WILL REMAIN CENTERED NEAR OKINAWA 
FOR THE FIRST 24 HOURS OF THE FORECAST. THE CENTER OF THE UPPER-
LEVEL STR WILL TRANSIT EASTWARDS TO BECOME ENTRENCHED TO THE 
NORTHEAST OF TS 20W BY TAU 36. AS THE STR MOVES EASTWARD, THE 
UPPER-LEVEL FLOW FROM THE NORTH WILL SERVE TO INCREASE PRESSURE AND 
SHEAR OVER THE SYSTEM, OFFSETTING THE VERY WARM WATERS AND MARGINAL 
OUTFLOW AND RESULTING IN ONLY SLOW INTENSIFICATION. BEYOND TAU 36, 
AS THE STR CONTINUES TO MOVE EAST, OUTFLOW IMPROVES, ALLOWING FOR 
THE SYSTEM TO RAPIDLY INTENSIFY, PEAKING AT 115 KNOTS BY TAU 72. 
MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT SINCE THE PREVIOUS 
FORECAST, WITH ALL MODELS EXCEPT THE ECMWF ENSEMBLE AND THE 
JAPANESE MODELS AGREEING ON A LANDFALL OVER CENTRAL TAIWAN BETWEEN 
TAUS 72 AND 96.   
   C. IN THE EXTENDED FORECAST, TS 20W WILL PASS OVER CENTRAL 
TAIWAN AND REEMERGE IN THE TAIWAN STRAIT BY TAU 96, THEN CONTINUE 
TO A SECOND LANDFALL OVER SOUTHEASTERN CHINA BEFORE TAU 120. THE 
SYSTEM WILL TURN SLIGHTLY MORE NORTHWESTWARD AFTER TAU 96, IN 
RESPONSE TO THE DEVELOPMENT OF A WEAKNESS IN THE STEERING STR. TS 
TALIM WILL WEAKEN SIGNIFICANTLY AFTER LANDFALL IN TAIWAN, BUT 
REMAIN A STRONG TYPHOON AFTER REEMERGENCE INTO THE TAIWAN STRAIGHT. 
AFTER SECOND LANDFALL IN CHINA, THE SYSTEM RAPIDLY DECAYS OVER 
LAND. DYNAMIC MODEL GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT IN 
THE LATER TAUS WITH ALL INDICATING A SECOND LANDFALL ALONG THE 
SOUTHEAST CHINA COASTLINE WITH A SPREAD OF ONLY 200 NM. THE 
FORECAST TRACK IS CONSISTENT WITH THE PREVIOUS TRACK AND SLIGHTLY 
NORTH AND SLOWER OF THE MULTI-MODEL CONSENSUS. WITH THE INCREASING 
AGREEMENT IN THE MODELS IN THE LATER PORTION OF THE FORECAST, THERE 
IS OVERALL HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// 
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