WDPN32 PGTW 282100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (KHANUN) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.6N 134.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 756 NM SOUTH-SOUTHEAST OF KADENA AB,
OKINAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A POORLY
ORGANIZED MEDIUM-SIZED SYSTEM WITH CONVECTION CONCENTRATED
SOUTHWARD OF A BROAD AND PARTIALLY EXPOSED LOW LEVEL CIRCULATION
(LLC). THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED
ON THE PARTLY EXPOSED LLC. THE INITIAL INTENSITY OF 35 KTS IS BASED
ON THE UNANIMOUS DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD, AND
REFLECTS THE 6-HR SUSTAINED EIR STRUCTURE. ANALYSIS INDICATES A
MARGINALLY FAVORABLE ENVIRONMENT WITH WARM SSTS IN THE PHILIPPINE
SEA AND STRONG POLEWARD OUTFLOW ALOFT OFFSET BY MODERATE VWS AND
SUBSIDENCE ALONG THE NORTHWEST QUADRANT DUE TO PRESSURE FROM THE
SUBTROPICAL HIGH TO THE NORTHWEST.

INITIAL WIND RADII BASIS: PERSISTENCE. 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER NEAR
EQUATORIAL RIDGE (NER) CENTERED EAST OF GUAM. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS D-PRINT: 36 KTS AT 281700Z
   CIMSS D-MINT: 35 KTS AT 281646Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: SUBSIDENCE ALONG THE NORTHWEST QUADRANT. 


ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TS KHANUN WILL CONTINUE ON A
NORTH-NORTHWESTWARD TRACK UNDER THE STEERING INFLUENCE OF THE NER
EAST OF GUAM. AFTER TAU 48, A SUBTROPICAL RIDGE (STR) TO THE 
NORTHEAST WILL ASSUME STEERING AND DRIVE THE SYSTEM ON A MORE 
NORTHWESTWARD TRAJECTORY TOWARD OKINAWA, PASSING JUST WEST OF THE 
ISLAND BEFORE TAU 72 PRIOR TO DRIFTING INTO THE EAST CHINA SEA AND 
MAKING LANDFALL SOUTH OF SHANGHAI AROUND TAU 108. THE MARGINALLY 
FAVORABLE ENVIRONMENT WILL FUEL A SLOW INTENSIFICATION TO 60KTS BY 
TAU 36. AFTERWARD, INCREASING POLEWARD OUTFLOW AS THE STEERING
MECHANISM SWITCHES TO THE STR WILL PROMOTE SIGNIFICANT
INTENSIFICATION TO A PEAK OF 90KTS BY TAU 72. AFTER TAU 72, A
BUILDING STR TO THE NORTH WILL ONCE AGAIN PROMOTE SUBSIDENCE
LEADING TO GRADUAL DISSIPATION TO 80 KTS PRIOR TO LANDFALL. AFTER
LANDFALL, INTERACTION WITH THE RUGGED CHINESE INTERIOR WILL MOSTLY
BE RESPONSIBLE FOR THE RAPID EROSION, AND BY TAU 120, TC 06W WILL
BE REDUCED TO 55KTS, POSSIBLY WEAKER, AS IT TRACKS FURTHER INLAND.    

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT WITH
A GRADUAL SPREAD TO A MERE 185NM BY TAU 72 THEN TO 516 NM BY TAU
120 WITH UKMET THE NOTABLE LEFT-OF-TRACK OUTLIER. IN VIEW OF THIS,
THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK UP TO TAU 72
THEN MEDIUM CONFIDENCE AFTERWARD. 

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