WDPN32 PGTW 091500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (CHANTHU) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.1N 126.0E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 303 NM EAST-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT SYSTEM WITH AN EYE-LIKE FEATURE THAT HAS WEAKENED SLIGHTLY 
OVER THE PAST SIX HOURS. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE EYE-LIKE FEATURE IN EIR. THE INITIAL 
INTENSITY IS BASED ON MULTI-AGENCY DVORAK INTENSITY ESTIMATES AND 
ADT WHICH ALL INDICATE THE SYSTEM IS CURRENTLY WEAKENING.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T7.0 - 140 KTS 
   KNES: T6.5 - 127 KTS
   CIMSS ADT: 109 KTS AT 091140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON (TY) 19W IS BEGINNING A MORE
NORTHWESTWARD TRACK AS IT BEGINS TO ROUND THE WESTERN EDGE OF THE
SUBTROPICAL RIDGE. AFTER TAU 48, THE SYSTEM WILL CROSS TAIWAN AS IT
TRACKS NORTHWARD AND EVENTUALLY CRESTS THE SUBTROPICAL RIDGE AXIS.
AFTER TAU 96, THE SYSTEM WILL TURN NORTH-NORTHEASTWARD ON THE
POLEWARD SIDE OF THE SUBTROPICAL RIDGE. TY 19W WILL REMAIN IN A
FAVORABLE ENVIRONMENT FOR THE EARLY PART OF THE FORECAST, SUSTAINING
IT ABOVE 100 KTS UNTIL ABOUT TAU 48, AT WHICH POINT LAND
INTERACTION WITH TAIWAN WILL BEGIN TO WEAKEN IT. THE SYSTEM WILL 
WEAKEN TO 85 KTS AS IT EXITS INTO THE TAIWAN STRAIT AROUND TAU 72.
AFTERWARDS, INCREASING VERTICAL WIND SHEAR AND DECREASING SEA
SURFACE TEMPERATURES WILL FURTHER WEAKEN THE SYSTEM TO 70 KTS BY
TAU 120.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT IN REGARDS
TO THE RECURVATURE TRACK FORECAST SOLUTION WITH ONLY A 150 NM
CROSS-TRACK SPREAD AT TAU 120. OF NOTE, OVER THE PAST 24 HOURS, THE
MODELS HAVE WALKED THE TRACK EASTWARD IN THE LATER TAUS, MAKING IT
MORE PROBABLE THE SYSTEM COULD IMPACT THE KOREAN PENINSULA OR
MAINLAND JAPAN. THERE IS ALSO GOOD AGREEMENT IN THE INTENSITY
GUIDANCE, AND THE FORECAST INTENSITY IS CONSISTENT WITH THE
MULTI-MODEL CONSENSUS. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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