WDPN32 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (KHANUN) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.0N 128.7E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 102 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A HIGHLY
SYMMETRIC TYPHOON WITH A ROUGHLY 20NM CRYSTAL CLEAR EYE AND TIGHTLY
WRAPPING BANDING FEATURES IN ALL QUADRANTS. A 010409Z AMSR2 89GHZ
COLOR COMPOSITE MICROWAVE IMAGE INDICATES A GENERALLY INTACT AND
THICK INNER EYEWALL WITH A MOAT-LIKE FEATURE POSSIBLY FORMING
AROUND IT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON A 20NM EYE VISIBLE IN MSI AND AMSR2 IMAGERY. THE INITIAL
INTENSITY OF 120 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A
RARE AGREEMENT AMONGST ALL AVAILABLE INTENSITY GUIDANCE. AGENCY
DVORAK INTENSITY ESTIMATES, CIMSS SATCON, ADT, D-MINT AND D-PRINT
ALL INDICATE 120 KTS WITH LITTLE VARIABILITY.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER STR
CENTERED OVER THE YELLOW SEA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 126 KTS AT 010451Z
   CIMSS ADT: 122 KTS AT 010530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: UPPER-LEVEL DRY AIR INTRUSION

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON 06W (KHANUN) IS FORECAST TO CONTINUE
TRACKING WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR
TO THE NORTH. THE SYSTEM IS FORECAST TO GRADUALLY WEAKEN OVER THE
NEXT 24 HOURS DUE TO PERSISTENT VERTICAL WIND SHEAR AND UPPER LEVEL
DRY AIR ENTRAINMENT. AFTER TAU 24, THE UPPER LEVEL STEERING PATTERN
WILL BEGIN TO SHIFT. THE STR TO THE NORTH WILL GRADUALLY SHIFT
WESTWARD AND A NEAR EQUATORIAL RIDGE (NER) TO THE SOUTH WILL
CONTINUE TO BUILD. BY TAU 48, THIS WILL SET UP A WEAK AND COMPETING
STEERING ENVIRONMENT THAT WILL LIKELY RESULT IN QUASI-STATIONARY OR
ERRATIC TRACK MOTION. DURING THIS TIME, SLOW TRACK SPEEDS COMBINED
WITH A TYPHOON STRENGTH LOW PRESSURE CENTER WILL UPWELL COPIOUS
AMOUNTS OF COOLER WATER BENEATH 06W. BY TAU 72, THIS COOLER WATER
COMBINED WITH ONGOING DRY AIR ENTRAINMENT WILL MORE RAPIDLY WEAKEN
THE SYSTEM. BY TAU 96, NOW TROPICAL STORM STRENGTH, THE RIDGES TO
THE NORTH AND SOUTH OF THE SYSTEM BOTH REORIENT TO THE WEST AND
FORCE 06W NORTHEASTWARD THROUGH THE REMAINING FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH
TAU 48, WITH ALL MEMBERS FOLLOWING THE JTWC TRACK FORECAST CLOSELY.
AFTER TAU 48 HOWEVER, TWO GROUPS BEGIN TO FORM, HWRF, EGRI AND
UKMET DRIVE THE SYSTEM INTO MAINLAND CHINA WHILE THE REMAINING
MEMBERS TAKE A SHARP TURN NORTHEASTWARD THROUGH THE FORECAST
PERIOD. FOR THIS REASON THE JTWC TRACK FORECAST IS PLACED INITIALLY
WITH MEDIUM CONFIDENCE AND WITH LOW CONFIDENCE THEREAFTER. SIMILAR
TO NUMERICAL MODEL OUTPUT, RELIABLE MODEL INTENSITY GUIDANCE IS IN
GOOD AGREEMENT INITIALLY, WITH ALL MEMBERS SLOWLY WEAKENING THE
SYSTEM THROUGH TAU 36. THE SPREAD IN MEMBER GUIDANCE GROWS AFTER
TAU 48 AS VARIOUS MEMBERS RESOLVE THE COMPLEX ENVIRONMENT AND
IMPACTS OF THE AFOREMENTIONED UPWELLING. JTWC REMAINS ON THE UPPER
END OF THE GUIDANCE ENVELOPE THROUGHOUT THE FORECAST PERIOD. FOR
THESE REASON THE JTWC INTENSITY FORECAST IS PLACED INITIALLY WITH
MEDIUM CONFIDENCE AND WITH LOW CONFIDENCE THEREAFTER.

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