WDPN31 PGTW 310900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KIROGI) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.0N 154.3E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 432 NM SOUTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 11W CONTINUES TO PROGRESS NORTHWARD WITH INCREASED
TRACK SPEED AS DEEP CONVECTION OBSCURES THE LOW-LEVEL CIRCULATION
CENTER (LLCC) AS SEEN ON THE ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI). ANIMATED WATER VAPOR IMAGERY DEPICTS A MODERATE 
POLEWARD OUTFLOW CHANNEL ENHANCED BY AN UPPER-LEVEL LOW POSITIONED TO 
THE NORTHWEST. A 310242Z AMSR2 89GHZ MICROWAVE IMAGE DEPICTS DEEP
CONVECTIVE BANDING ON THE NORTHERN SEMICIRCLE WRAPPING INTO A
DEFINED MICROWAVE EYE FEATURE. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON A COMBINATION WITH AGENCY DVORAK
POSITION FIXES. A 310240Z AMSR2 WINDSPEED IMAGE SHOWS A 55-60 KNOT
SWATH ON THE NORTHWESTERN SEMICIRCLE. THE INITIAL INTENSITY OF 60 
KNOTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AMSR2 WINDSPEED 
IMAGE, AND AGENCY DVORAK INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE
(STR) POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   CIMSS ADT: 69 KTS AT 310210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 11W WILL CONTINUE TO TRACK GENERALLY
NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE 
(STR) POSITIONED TO THE EAST THROUGH TAU 72. AFTER TAU 72, THE STR 
WILL SHIFT AND EXTEND WESTWARD, CAUSING 11W TO TRACK WEST-
NORTHWESTWARD SOUTH OF KYUSHU BY THE END OF THE FORECAST PERIOD. THE 
SYSTEM HAS CONTINUED TO STRENGTHEN DUE TO FAVORABLE ROBUST POLEWARD 
OUTFLOW FROM AN UPPER-LEVEL TROUGH TO THE WEST IN ADDITION TO WARM SEA 
SURFACE TEMPERATURES (SST). HOWEVER, HIGHER VERTICAL WIND SHEAR (VWS), 
LESS FAVORABLE OUTFLOW, AND DRY AIR ENTRAINMENT ARE EXPECTED TO 
INCREASE OVER THE NEXT 24-36 HOURS. THUS, THE ENVIRONMENT WILL BECOME
INCREASINGLY LESS FAVORABLE THROUGHOUT THE FORECAST PERIOD,
RESULTING IN A GRADUAL WEAKENING TREND.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT THROUGH TAU 72, ASIDE FROM NAVGEM, WHICH IS THE SOLE
OUTLIER TO THE RIGHT OF TRACK. AFTER TAU 72 AND FOR THE REMAINING
TRACK FORECAST, THE MODEL GUIDANCE INCREASES IN BOTH CROSS AND
ALONG-TRACK SPREAD. THEREFORE, THE JTWC TRACK FORECAST IS PLACED
WITH HIGH CONFIDENCE THROUGH TAU 72, WITH MEDIUM CONFIDENCE
THROUGHOUT THE REMAINDER OF THE FORECAST. THE INTENSITY GUIDANCE IS
IN OVERALL GOOD AGREEMENT, WITH MOST MEMBERS INDICATING A GRADUAL
WEAKENING TREND BEGINNING AFTER TAU 24 CONTINUING THROUGH THE
FORECAST PERIOD. FOR THIS REASON, THE JTWC INTENSITY FORECAST IS
PLACED WITH OVERALL MEDIUM CONFIDENCE.

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