WDPN31 PGTW 201500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (IN-FA) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.6N 129.0E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 131 NM SOUTH-SOUTHEAST OF KADENA AB, JAPAN
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DENSE
CONVECTION SURROUNDING A 13 NM DIAMETER EYE AND ROBUST POLEWARD
OUTFLOW ALOFT. THE CONTINUED PRESENCE OF THE EYE FEATURE LENDS HIGH
CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS
ASSESSED AT 75 KTS WITH HIGH CONFIDENCE BASED ON THE HIGH DEGREE OF
AGREEMENT IN MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES AND
CIMSS SATCON AND ADVANCED DVORAK TECHNIQUE CURRENT INTENSITY
ESTIMATES. DESPITE THE PRESENCE OF ROBUST POLEWARD OUTFLOW,
ANALYSIS OF THE ANIMATED SATELLITE IMAGERY REVEALS A CONTINUED LACK
OF EQUATORWARD OUTFLOW DUE TO UPPER LEVEL RIDGING TO THE WEST.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP LAYER STR
POSITIONED TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 79 KTS AT 201009Z
   CIMSS ADT: 75 KTS AT 201210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TY IN-FA WILL CONTINUE A WESTWARD TRACK
THROUGH TAU 48 UNDER THE INFLUENCE OF THE STEERING RIDGE. FAVORABLE
ENVIRONMENTAL CONDITIONS, ALONG WITH INCREASINGLY ROBUST POLEWARD
OUTFLOW, WILL ALLOW TY IN-FA TO INTENSIFY, POSSIBLY RAPIDLY, TO 105
KTS BY TAU 48 AT WHICH TIME IT WILL HAVE PASSED SOUTH OF OKINAWA,
JAPAN. THEREAFTER, A REORIENTATION IN THE STEERING RIDGE DUE TO
INTERACTION WITH A MIDLATITUDE TROUGH WILL LEAD TY IN-FA TO BEGIN
ROUNDING THE STR ON A GENERALLY NORTHWESTWARD TRACK. THE SYSTEM
WILL THEN GRADUALLY WEAKEN TO 90 KTS BY TAU 72 DUE TO AN EROSION OF
THE FAVORABLE UPPER LEVEL PATTERN. TY IN-FA WILL TRACK ALONG THE
NORTHERN TIP OF TAIWAN AND MAKE LANDFALL UPON MAINLAND CHINA
BETWEEN TAUS 92 AND 120. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK AND INTENSITY GUIDANCE IS
IN GENERALLY GOOD AGREEMENT THROUGH TAU 48. ALL MEMBERS OF THE JTWC
MULTI-MEMBER CONSENSUS AGREE ON A GENERALLY WESTWARD TRACK THROUGH
TAU 48 WITH THE EXCEPTION OF THE GALWEM SOLUTION THAT CONTINUES TO
PROVIDE A SOUTHWESTWARD TRACK THROUGH THAT TIME. THEREAFTER, ALL
MODELS AGREE ON A SUBSEQUENT RECURVE AROUND THE STEERING RIDGE.
MODEL SOLUTIONS DIVERGE, HOWEVER, ON THE DEGREE OF THIS RECURVATURE
DUE TO UNCERTAINTY IN THE INTERACTION OF AN INCOMING MIDLATITUDE
TROUGH WITH THE STEERING RIDGE. THE GFS (BOTH DETERMINISTIC AND
ENSEMBLE MEAN) SOLUTIONS PROVIDE TRACKS THAT LIE NORTH OF TAIWAN
THROUGH THE REMAINDER OF THE FORECAST PERIOD. THIS IS IN CONTRAST
TO THE GALWEM, UKMET (BOTH DETERMINISTIC AND ENSEMBLE) AND NAVGEM
SOLUTIONS THAT BRING THE VORTEX OVER TAIWAN WITH A MORE GRADUAL
RECURVEATURE. THE OVERALL TIGHT AGREEMENT IN MODEL GUIDANCE LENDS
HIGH CONFIDENCE IN THE EARLY TAUS (0-72 HRS) OF THE JTWC FORECAST
TRACK AND MEDIUM CONFIDENCE THEREAFTER.

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