WDPN31 PGTW 182100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.4N 131.9E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 290 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AREA OF
VIGOROUS DEEP CONVECTION WRAPPING INTO A RAGGED CENTRAL CORE.
TRACKING OF THE CENTER HAS BEEN DIFFICULT IN THE OVERNIGHT HOURS,
HOWEVER AN 181708Z AMSR2 IMAGE ARRIVED LATE IN THE CYCLE TO ASSIST.
THE AMSR LOW LEVEL CIRCULATION CENTER (LLCC) APPEARS BROAD AND
ILL-DEFINED, WITH DEEP CONVECTION DISPLACED TO THE NORTHEAST. THE
INITIAL INTENSITY WAS ROUNDED UP FROM THE KNES T3.0 (45 KNOTS) TO
50 KNOTS BASED ON THE AMSR WINDSPEED DATA PRODUCT. THE LARGE SIZE
OF 09W COMBINED WITH REMNANTS OF DRY AIR ARE INHIBITING THE SYSTEM
FROM INTENSIFYING AT A FASTER RATE, DESPITE AN OTHERWISE FAVORABLE
ENVIRONMENT.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK AND PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED OVER
HONSHU EXTENDING SOUTHWARD OVER THE NORTHEASTERN AND EASTERN
PERIPHERY OF THE SYSTEM.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 44 KTS AT 181110Z
   CIMSS ADT: 31 KTS AT 181740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: UNCERTAINTY IN INITIAL POSITION IS RESULTING
IN SLIGHT SHIFTS IN THE FORECAST, AND NUMERICAL GUIDANCE IS LIKELY
HAVING SIMILAR ISSUES. THE SYSTEM IS EXPECTED TO TRACK
WEST-NORTHWESTWARD TO WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE
STR THROUGH THE FORECAST PERIOD. ADDITIONAL CONSOLIDATION AND
INTENSIFICATION IS EXPECTED AS THE DEEP UPPER LOW IN THE WEST SEA
CONTINUES TO FILL AND DRIFT POLEWARD, ENHANCING POLEWARD OUTFLOW. 
GRADUAL INTENSIFICATION IS FORECAST DUE TO THE BROAD SIZE, REACHING 
A PEAK INTENSITY OF AROUND 85 KNOTS AS THE SYSTEM APPROACHES TAIWAN. 
AFTER TAU 96, INTERACTION WITH TAIWAN WILL WEAKEN THE SYSTEM 
SLIGHTLY. THE DEGREE OF WEAKENING IS HIGHLY DEPENDENT ON WHETHER THE 
ACTUAL TRACK TAKES IN-FA OVER LAND, OR KEEPS IT OVER WATER.  

MODEL DISCUSSION: CONFIDENCE IN THE TRACK FORECAST THROUGH TAU 72
IS MEDIUM GIVEN REASONABLE AGREEMENT AMONG THE MULTI-MODEL
CONSENSUS. BEYOND TAU 72 THE SPREAD GREATLY INCREASES, WITH ECMF A
NOTABLE OUTLIER ON A MORE NORTH-WESTWARD TRACK. DUE TO THE THE
PRESENCE OF 10W AND EXPECTED FUTURE DEVELOPMENT IN THE WAKE OF 09W,
THERE IS POTENTIAL FOR DIRECT CYCLONE INTERACTION, A KNOWN SOURCE
OF INCREASED NUMERICAL MODEL ERROR. THERE IS LOW CONFIDENCE IN THE
JTWC INTENSITY FORECAST WITH A LARGE SPREAD IN INTENSITY GUIDANCE. 


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