WDPN31 PGTW 290300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (HINNAMNOR) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.3N 145.3E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 937 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A COMPACT,
SYMMETRICAL SYSTEM WITH SPIRAL BANDING FROM THE NORTHERN PERIPHERY
THAT HAS WRAPPED TIGHTER INTO AN OBSCURED LOW LEVEL CIRCULATION 
CENTER (LLCC). THE CENTRAL DENSE OVERCAST FEATURE, WHICH IS OBSCURING 
THE LLCC HAS A FORMATIVE EYE NEAR THE CENTER. THE INITIAL POSITION 
IS PLACED WITH HIGH CONFIDENCE BASED ON A DEFINED EYE FEATURE IN
THE 2313Z GPM 37GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 55KTS
IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON AGENCY AND AUTOMATED 
DVORAK ESTIMATES THAT REFLECT THE 6-HR STRUCTURAL IMPROVEMENT AND 
CONSISTENT WITH A FORMATIVE EYE. THE ENVIRONMENT REMAINS FAVORABLE 
WITH STRONG EQUATORWARD OUTFLOW, MODERATE VERTICAL WIND SHEAR, AND 
WARM SSTS.

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
EXTENSION TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 53 KTS AT 282208Z
   CIMSS ADT: 53 KTS AT 282340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: S HINNAMNOR WILL TRACK GENERALLY WESTWARD TOWARD 
OKINAWA UNDER THE STEERING STR. AFTER TAU 72, A SECONDARY STR OVER 
CENTRAL CHINA, EMERGING BEHIND A TRANSITORY SHORTWAVE TROUGH, AND A 
NEAR EQUATORIAL RIDGE TO THE SOUTHEAST WILL COMPETE FOR STEERING, 
FORCING THE SYSTEM TO BECOME QUASI-STATIONARY (QS) IN A COL AREA. THE 
AFOREMENTIONED FAVORABLE CONDITIONS WILL PROMOTE GRADUAL THEN RAPID 
INTENSIFICATION TO A PEAK OF 130KTS BY TAU 72. AFTERWARD, COOLING SST 
DUE TO UPWELLING INDUCED BY THE SYSTEM BEING QS IN THE COL WILL 
WEAKEN THE SYSTEM TO 105KTS BY TAU 100.

MODEL DISCUSSION: THE MAJORITY OF AVAILABLE NUMERICAL MODELS IS IN
BROAD AGREEMENT UP TO TAU 72. AFTERWARD, TWO MODELS - NVGM AND 
UKMET - RECURVE THE VORTEX TOWARD JAPAN IN RESPONSE TO THE TRANSITORY 
SHORTWAVE TROUGH. THE MAIN PACK CONTINUES WESTWARD TOWARD THE COL 
AREA. IN VIEW OF THIS, AND GIVEN THE UNCERTAINTIES IN TRACK MOTION 
INHERENT IN A COL, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK, LAID 
NEAR THE CONSENSUS OF THE MAIN PACK, AND INTENSITY FORECASTS UP TO 
TAU 72 THEN LOW CONFIDENCE AFTERWARD. 

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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