WDPN32 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (AMPIL) 
WARNING NR 06//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 12W (AMPIL), LOCATED APPROXIMATELY 414 NM 
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA HAS TRACKED EAST-NORTHEASTWARD 
AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL 
SATELLITE IMAGERY DEPICTS A LARGE SYSTEM, APPROXIMATELY 500NM 
DIAMETER, WITH AN EXTENSIVE BAND OF PERSISTENT DEEP CONVECTION OVER 
THE SOUTHERN SEMICIRCLE WRAPPING INTO THE NORTHEAST QUADRANT OF A 
BROAD, PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC). A 
182142Z SSMIS 37GHZ IMAGE PROVIDES EVIDENCE THAT THE SYSTEM IS 
SLOWLY CONSOLIDATING WITH IMPROVED CONVECTIVE BANDING, HOWEVER, THE 
LLCC REMAINS ELONGATED (APPROXIMATELY 90-100NM DIAMETER). 
CONSEQUENTLY, THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION. 
UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE, COMPLEX 
ENVIRONMENT WITH TWO TUTT CELLS POSITIONED OVER THE NORTHERN 
SEMICIRCLE HINDERING DEVELOPMENT, AND STRONG DIFFLUENT FLOW OVER THE 
SOUTHERN SEMICIRCLE FUELING EXTENSIVE DEEP CONVECTION. SST VALUES 
(28-29C) REMAIN FAVORABLE WHILE OCEAN HEAT CONTENT VALUES ARE LOW 
AND UNFAVORABLE. DUE TO THE ASYMMETRIC NATURE OF THE CONVECTIVE 
STRUCTURE AND LACK OF DEEP CONVECTION OVER THE LLCC, DVORAK 
INTENSITY ESTIMATES REMAIN LOW AND RANGE FROM T1.5 TO T2.5 (25 TO 35 
KNOTS). THE INITIAL INTENSITY IS HEDGED ABOVE THE HIGHER ESTIMATE OF 
35 KNOTS BASED ON THE IMPROVED CONVECTIVE STRUCTURE AND A 182143Z 
SATCON ESTIMATE OF 47 KNOTS. TS 12W IS LOCATED NORTHWEST OF THE NEAR-
EQUATORIAL RIDGE (NER) AND SOUTH OF A STRONG EAST-WEST ORIENTED 
SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. 
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE. 
   B. TS 12W IS FORECAST TO TRACK GENERALLY POLEWARD ALONG THE 
WESTERN PERIPHERY OF THE NER UNTIL TAU 24 AT WHICH TIME THE SYSTEM 
WILL TRANSITION TO THE STEERING INFLUENCE OF THE STR. DUE TO THE 
MARGINALLY-FAVORABLE UPPER-LEVEL ENVIRONMENT, WHICH IS FORECAST TO 
PERSIST, TS AMPIL IS EXPECTED TO INTENSIFY AT A SLOWER-THAN-
CLIMATOLOGICAL RATE OF 10 KNOTS PER DAY THROUGH TAU 48. THE SYSTEM 
SHOULD PEAK AT TAU 48 TO 60 KNOTS. WITH THE EXCEPTION OF HWRF, THE 
SOLE OUTLIER WELL TO THE NORTH, NUMERICAL MODEL GUIDANCE IS IN GOOD 
AGREEMENT WITH A 115NM SPREAD IN SOLUTIONS AT TAU 48. THE BULK OF 
THE GUIDANCE INDICATES A TRACK OVER AND TO THE SOUTH OF OKINAWA, 
WHICH IS THE MORE LOGICAL TRACK CONSIDERING THE ORIENTATION AND 
STRENGTH OF THE STR. THERE IS, HOWEVER, UNCERTAINTY IN THE TIMING OF 
THE NORTHWESTWARD TRACK CHANGE AND THE TRACK SPEEDS DURING THIS 
TRANSITION, THEREFORE, CONFIDENCE IS MODERATE THROUGH TAU 72. 
SURFACE WINDS ARE FORECAST TO REMAIN EXTENSIVE AND ROBUST OVER THE 
NORTHERN SEMICIRCLE DUE TO THE STRONG GRADIENT ASSOCIATED WITH THE 
SYSTEM AND ADJACENT SURFACE HIGH. 
   C. AFTER TAU 72, TS 12W IS FORECAST TO ACCELERATE NORTHWESTWARD 
UNDER THE STEERING INFLUENCE OF THE STR AND IS EXPECTED TO MAKE 
LANDFALL NEAR TAU 84 ALONG THE EAST COAST OF CHINA, SOUTH OF 
SHANGHAI. THE SYSTEM WILL CONTINUE TO TRACK INLAND WHILE WEAKENING 
STEADILY. NUMERICAL MODEL GUIDANCE DIVERGES AFTER TAU 72 WITH A 
520NM SPREAD IN SOLUTIONS AT TAU 120 (300NM IF HWRF IS EXCLUDED), 
INDICATING INCREASING UNCERTAINTY AS TO THE EXACT LANDFALL LOCATION. 
OVERALL, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST (I.E., HIGH 
UNCERTAINTY) DUE TO THE AFOREMENTIONED ISSUES AS WELL AS SIGNIFICANT 
UNCERTAINTY IN THE INITIAL LOCATION.//
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