WDPN31 PGTW 311500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KIROGI) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.0N 153.7E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 372 NM SOUTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
PERSISTENT DEEP CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION
CENTER (LLCC). ANIMATED WATER VAPOR IMAGERY DEPICTS A MODERATE
POLEWARD OUTFLOW CHANNEL ENHANCED BY AN UPPER-LEVEL LOW POSITIONED
TO THE NORTHWEST. THE INITIAL POSITION IS PLACED WITH MEDIUM 
CONFIDENCE BASED ON THE GROUPING OF AGENCY POSITION FIXES. THE INITIAL 
INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A 
CONSENSUS OF SUBJECTIVE DVORAK INTENSITY ESTIMATES AND AUTOMATED 
SATELLITE INTENSITY ESTIMATES FROM D-PRINT AND D-MINT RANGING FROM 54 
AND 53 KNOTS, RESPECTIVELY. ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY 
FAVORABLE DUE TO WARM (29-30C) SEA SURFACE TEMPERATURES (SSTS), GOOD 
POLEWARD OUTFLOW, OFFSET BY MODERATE (20-25 KNOTS) VERTICAL WIND SHEAR 
(VWS).

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T4.0 - 65 KTS

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TROPICAL STROM 11W (KIROGI) IS FORECAST TO
TRACK NORTH-NORTHWESTWARD, THEN NORTHWESTWARD ALONG THE WESTERN
PERIPHERY OF THE STR THROUGH TAU 48. AFTER TAU 48, TS 11W WILL TURN
WEST-NORTHWESTWARD AS THE STR TO THE NORTHEAST BUILDS AND EXTENDS
WESTWARD. BY TAU 72, TS 11W IS EXPECTED TO CONTINUE TO TRACK
WEST-NORTHWESTWARD, THEN GENERALLY WESTWARD TOWARD SOUTHERN KYUSHU
THROUGH THE END OF THE FORECAST. NO SIGNIFICANT ENVIRONMENTAL
CHANGES ARE EXPECTED OVER THE NEXT 12-24 HOURS OF THE FORECAST,
WITH SUPPORTIVE SSTS AND ROBUST POLEWARD OUTFLOW COMPETING WITH VWS
AND DRY AIR ENTRAINMENT. THE SYSTEM IS FORECAST TO MAINTAIN A
STEADY STATE IN TERMS OF INTENSITY BUT THEN BEGIN A STEADY WEAKENING
TREND AS OUTFLOW BECOMES LESS FAVORABLE AND DRY AIR ENTRAINMENT
INCREASES. THUS, THE UNFAVORABLE ENVIRONMENTAL FACTORS WILL RESULT
IN A GRADUAL WEAKENING TREND THROUGHOUT THE FORECAST PERIOD.   

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINS IN
GOOD AGREEMENT THROUGH TAU 72, ASIDE FROM NAVGEM, WHICH IS THE SOLE
OUTLIER TO THE RIGHT OF TRACK. AFTER TAU 72, MODEL TRACK GUIDANCE
INCREASES IN BOTH CROSS AND ALONG-TRACK SPREAD. THEREFORE, THE JTWC
TRACK FORECAST IS PLACED NEAR THE CONSENSUS MEAN 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 STEADY WEAKENING
TREND 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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