WDPN31 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (IN-FA) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.7N 129.7E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 149 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP
CONVECTION, ROBUST POLEWARD OUTFLOW IN THE UPPER LEVELS AND A
RAGGED, 35 NM DIAMETER EYE THAT LENDS HIGH CONFIDENCE IN THE
INITIAL POSITION. THE HIGH DEGREE OF AGREEMENT IN THE MULTIAGENCY
DVORAK CURRENT INTENSITY ESTIMATES LENDS HIGH CONFIDENCE IN THE
INITIAL INTENSITY, WHICH IS PLACED HIGHER THAN OBJECTIVE DVORAK AND
SATCON ESTIMATES FROM CIMSS. ANIMATED WATER VAPOR IMAGERY DEPICTS A
SLIGHT DEGREE OF DRY AIR ENTRAINMENT ALONG THE SOUTHERN AND
SOUTHEASTERN PERIPHERY OF THE SYSTEM.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 53 KTS AT 200412Z
   CIMSS ADT: 39 KTS AT 200230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 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 72 UNDER THE INFLUENCE OF THE STEERING RIDGE. THE
SYSTEM WILL INTENSIFY ONLY SLIGHTLY OVER THE NEXT 6 HOURS DUE TO A
SLIGHT INCREASE IN VWS AND THE ENTRAINMENT OF DRY AIR ALONG THE
SOUTHERN AND SOUTHEASTERN PERIPHERY OF THE SYSTEM. AFTER TAU 6, A
REPOSITIONING OF THE UPPER LEVEL RIDGE POSITIONED TO THE NORTH OF
THE SYSTEM WILL ALLOW FOR ENHANCED POLEWARD OUTFLOW. THIS
REPOSITIONING, ALONG WITH DECREASING VWS AND CONTINUED WARM SST,
WILL ALLOW TY IN-FA TO INTENSIFY, POSSIBLY RAPIDLY, TO 95 KTS BY
TAU 48 AT WHICH TIME IT WILL HAVE PASSED SOUTH OF OKINAWA, JAPAN.
THE SYSTEM WILL THEN GRADUALLY WEAKEN TO 85 KTS BY TAU 72 DUE TO AN
EROSION OF THE FAVORABLE UPPER LEVEL PATTERN. THEREAFTER, TY IN-FA
WILL BEGIN A NORTHWESTWARD TRACK AS IT BEGINS TO ROUND THE STEERING
RIDGE. THIS TRACK WILL BRING IT ALONG THE NORTHERN TIP OF TAIWAN
AND INTO MAINLAND CHINA BETWEEN TAUS 92 AND 120. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK AND INTENSITY GUIDANCE IS
IN GENERALLY GOOD AGREEMENT THROUGH TAU 72. ALL MEMBERS OF THE JTWC
MULTI-MEMBER CONSENSUS AGREE ON A GENERALLY WESTWARD TRACK THROUGH
TAU 72 WITH THE EXCEPTION OF THE GALWEM SOLUTION THAT PROVIDES A
SOUTHWESTWARD TRACK THROUGH THAT TIME. THEREAFTER, ALL MODELS AGREE
ON A SUBSEQUENT RECURVE AROUND THE STEERING RIDGE. THE DEGREE OF
THIS RECURVATURE, HOWEVER, RESULTS IN A HIGH DEGREE OF MODEL
SPREAD AFTER TAU 72. THE NAVGEM AND GFS (BOTH DETERMINISTIC AND
ENSEMBLE MEAN) SOLUTIONS BOTH 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
ECMWF (BOTH DETERMINISTIC AND ENSEMBLE) SOLUTIONS THAT BRING THE
VORTEX OVER TAIWAN WITH A MORE GRADUAL RECURVEATURE. THIS DIVERGENCE 
IN MODEL SOLUTIONS IS THE RESULT OF UNCERTAINTY IN THE TIMING AND 
DEGREE OF INTERACTION BETWEEN THE STEERING RIDGE AND AN INCOMING 
UPPER LEVEL TROUGH PROPAGATING FROM THE WEST. MODELS ALSO GENERALLY 
AGREE ON A SLIGHT PERIOD OF LOW INTENSIFICATION OVER THE NEXT 6 
HOURS 
WITH SUBSEQUENT GRADUAL OR POSSIBLY RAPID INTENSIFICATION THEREAFTER 
THROUGH TAU 48. THE OVERALL TIGHT AGREEMENT IN MODEL GUIDANCE LENDS 
HIGH CONFIDENCE IN BOTH TRACK AND INTENSITY IN THE EARLY TAUS (0-72 
HRS) 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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