WDPN31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 12W (HINNAMNOR)    
WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.8N 125.5E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 309 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 52 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SLIGHT
WEAKENING AND ELONGATION OF THE CONVECTIVE CORE WITH WARMING CLOUD
TOP TEMPERATURES AND A COOLING EYE TEMPERATURE NEAR -2C.
CONSEQUENTLY, THE DVORAK DATA-T ESTIMATES HAVE DECREASED TO T6.5
(127 KNOTS) WITH CURRENT INTENSITY ESTIMATES PERSISTING AT 7.0 (140
KNOTS). THE INITIAL INTENSITY OF 135 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE AND WAS REDUCED SLIGHTLY TO REFLECT THE WEAKENING TREND
EVIDENT IN EIR. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS A 10NM ROUND EYE, WHICH SUPPORTS THE INITIAL POSITION WITH
HIGH CONFIDENCE. SUBSEQUENT MSI AFTER 010600Z INDICATES THE SYSTEM
CONTINUES TO SLOW SIGNIFICANTLY AND THE EYE IS BECOMING CLOUD-
FILLED AS THE SYSTEM CONTINUES TO WEAKEN AND STALL. ENVIRONMENTAL 
CONDITIONS HAVE DEGRADED WITH INCREASING EASTERLY VWS AND DECREASING 
POLEWARD OUTFLOW DUE TO CONVERGENCE ASSOCIATED WITH AN UPPER-LEVEL 
TROUGH TO THE NORTHEAST AND AN UPPER-LEVEL RIDGE TO THE NORTHWEST. 

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT WITH A
SUBTROPICAL RIDGE (STR) TO THE WEST, ANOTHER STR TO THE EAST AND
NORTHEAST, AND A NEAR-EQUATORIAL RIDGE TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T7.0 - 140 KTS 
   KNES: T7.0 - 140 KTS 
   CIMSS SATCON: 141 KTS AT 010501Z
   CIMSS ADT: 140 KTS AT 010540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 25-30 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: UPWELLING COOLER WATER

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: STY 12W IS FORECAST TO SLOW AND STALL THROUGH 
THE NEXT 24-36 HOURS WITH ERRATIC, QUASI-STATIONARY MOTION EXPECTED. 
THE SYSTEM WILL WEAKEN PRIMARILY DUE TO COOL UPWELLING WATER TO 
AROUND 100 KNOTS. AFTER TAU 36, A MIDLATITUDE SHORTWAVE TROUGH IS 
EXPECTED TO DIG OVER CENTRAL CHINA, WHICH WILL WEAKEN THE WESTERN STR 
AND ALLOW THE SUBTROPICAL RIDGE TO THE EAST TO ASSUME THE PRIMARY 
STEERING INFLUENCE. CONSEQUENTLY, STY 12W WILL ACCELERATE NORTHWARD 
ALONG THE WESTERN PERIPHERY OF THE STR THROUGH TAU 72. RE-
INTENSIFICATION IS ANTICIPATED AS POLEWARD OUTFLOW IMPROVES INTO THE 
STRONG WESTERLIES OVER THE KOREAN PENINSULA WITH FAVORABLE SST VALUES 
NEAR 30C. STY 12W WILL RECURVE TOWARD SOUTH KOREA AND WESTERN JAPAN 
AS IT TRACKS AROUND THE STR AXIS AND BEGINS TO INTERACT WITH THE 
MIDLATITUDE WESTERLIES. THE SYSTEM WILL COMMENCE EXTRA-TROPICAL 
TRANSITION NEAR CHEJU-DO AND WILL RAPIDLY TRANSITION INTO AN EXTRA-
TROPICAL LOW IN THE SEA OF JAPAN.     

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT 
WITH A 125-150NM SPREAD IN SOLUTIONS THROUGH THE FORECAST PERIOD, 
HOWEVER, THE OVERALL CONFIDENCE IN THE JTWC FORECAST TRACK IS 
ASSESSED AT MEDIUM DUE TO UNCERTAINTY IN THE TRACK MOTION DURING THE 
QUASI-STATIONARY PHASE. THIS UNCERTAINTY IS REFLECTED IN THE 010000Z 
ECMWF (EPS) AND GFS (GEFS) ENSEMBLE GUIDANCE, WHICH SHOWS SOME 
SOLUTIONS CLOSER TO OKINAWA AS STY 12W TRACKS POLEWARD. THERE IS 
MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST THROUGH TAU 72 WITH  
A LARGE SPREAD IN INTENSITY GUIDANCE. AFTER TAU 72, THE INTENSITY 
FORECAST IS MORE UNCERTAIN DUE TO THE EXTRA-TROPICAL TRANSITION AND 
INTERACTION WITH LAND.    

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