WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.3N 125.6E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 335 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS ERODING
DEEP CONVECTION OVER THE NORTHERN SEMICIRCLE DUE TO INCREASING
NORTHEASTERLY VERTICAL WIND SHEAR (VWS). HOWEVER, THE SYSTEM HAS
RETAINED A CLOUD-FILLED EYE AND FRAGMENTED SPIRAL BANDING OVER THE
WESTERN SEMICIRCLE. A 011303Z AMSR2 89GHZ MICROWAVE IMAGE STILL
SHOWS A ROUND 12NM MICROWAVE EYE FEATURE WITH THE BULK OF THE CORE
CONVECTION OVER THE SOUTHERN SEMICIRCLE AND EXTENSIVE DEEP
CONVECTIVE BANDING AROUND THE WESTERN AND SOUTHERN PERIPHERIES. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AMSR2
IMAGE. DVORAK DATA-T ESTIMATES HAVE CONTINUED TO DECREASE AND RANGE
FROM T5.5 TO T6.0 (102-115 KNOTS) WITH CURRENT INTENSITY ESTIMATES
RANGING FROM 6.5 TO 7.0 (127 TO 140 KNOTS). ADT ESTIMATES HAVE
DECREASED QUICKLY TO 115 KNOTS. THE INITIAL INTENSITY OF 120 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF ALL THE
ESTIMATES. 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: PERSISTENCE 

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: T6.5 - 127 KTS
   CIMSS ADT: 115 KTS AT 011140Z

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: TY 12W IS FORECAST TO SLOW AND STALL THROUGH
THE NEXT 24 HOURS WITH ERRATIC, QUASI-STATIONARY MOTION EXPECTED. THE 
SYSTEM WILL WEAKEN PRIMARILY DUE TO COOL UPWELLING WATER TO AROUND 90 
KNOTS. AFTER TAU 24, 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, TY 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. TY 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 100NM SPREAD IN SOLUTIONS THROUGH TAU 72. THE OVERALL 
CONFIDENCE IN THIS PORTION OF 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 010600Z ECMWF 
(EPS) AND GFS (GEFS) ENSEMBLE GUIDANCE, WHICH SHOWS SOME SOLUTIONS 
CLOSER TO OKINAWA AS TY 12W TRACKS POLEWARD. AFTER TAU 72, THERE ARE 
MAJOR DIFFERENCES IN ALONG-TRACK SPEEDS WITH GFS INDICATING A FAST 
TRACK INTO NORTHEAST CHINA, HOWEVER, EXAMINATION OF THE GFS FIELDS 
INDICATES THE TRACKER IS MERGING THE SYSTEM INTO A STRONG BAROCLINIC 
SYSTEM. THE BULK OF THE DETERMINISTIC AND PROBABILISTIC GUIDANCE 
INDICATES THE SYSTEM WILL TRACK INTO THE CENTRAL SEA OF JAPAN, 
HOWEVER, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK DUE TO THE 
ALONG-TRACK DIFFERENCES. 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: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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