WDPN31 PGTW 271500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (NESAT) WARNING NR 17//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 20W (NESAT), LOCATED APPROXIMATELY 180 NM 
NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 12 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY 
SHOWS A WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED 
WITH CENTRAL DEEP CONVECTION AND A STRONG CONVECTIVE BAND TO THE 
SOUTH. THE INITIAL POSITION IS BASED ON THE IR IMAGERY AND 
EXTRAPOLATED FROM A 270958Z 37GHZ SSMIS, WHICH DEPICTS AN ELONGATED 
LLCC. THE INITIAL INTENSITY IS BASED ON THE PGTW, KNES, AND RJTD 
DVORAK ESTIMATES RANGING FROM 65 TO 90 KNOTS. WATER VAPOR IMAGERY 
DEPICTS EXCELLENT EQUATORWARD OUTFLOW AND LIMITED POLEWARD OUTFLOW.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY.
   B. TY 20W IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF A 
DEEP LAYER SUBTROPICAL STEERING RIDGE, WHICH IS EXPECTED TO REMAIN 
THE MAIN STEERING INFLUENCE THROUGHOUT THE FORECAST PERIOD. TY 20W 
IS FORECAST TO INTENSIFY AS IT TRACKS OVER WARM WATER AND MAINTAINS 
GOOD OUTFLOW. AFTER TAU 48, TY 20W WILL WEAKEN AS IT CROSSES OVER 
HAINAN.
  C. AFTER TAU 72, TY 20W WILL CONTINUE TO WEAKEN AS IT MAKES 
LANDFALL OVER NORTHERN VIETNAM AND BEGIN TO DISSIPATE AS A 
SIGNIFICANT TROPICAL CYCLONE OVER LAND. NUMERICAL MODEL GUIDANCE IS 
IN GOOD AGREEMENT. THEREFORE, THIS FORECAST IS IN GOOD AGREEMENT 
WITH MODEL CONSENSUS.//
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