WDPN32 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (KHANUN) WARNING NR 
037//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.8N 127.6E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 79 NM NORTH OF KADENA AB
   MOVEMENT PAST 6 HOURS: EASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A LARGE
TROPICAL STORM FORCE CIRCULATION WITH DEEP CONVECTIVE BANDING
FEATURES IN ALL QUADRANTS. A 050143Z ASCAT-C SCATTEROMETERY PASS
REVEALS A SIZABLE CIRCULATION WITH AN RMW APPROACHING 80NM AND AN
ASYMMETRIC WIND FIELD UNFORTUNATELY FAVORING THE SOUTHEASTERN
QUADRANT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON MSI AND ASCAT-C DATA. THE INITIAL INTENSITY OF 55 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE PREPONDERANCE OF
EVIDENCE, INCLUDING AGENCY DVORAK INTENSITY ESTIMATES, CIMSS
D-PRINT AND SATCON SUPPORTING THE JTWC INITIAL INTENSITY, WHILE
CIMSS ADT AND AIDT REMAIN MUCH LOWER.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NEAR-EQUATORIAL RIDGE (NER) TO THE
SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 61 KTS AT 050220Z
   CIMSS ADT: 32 KTS AT 050530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: IMPROVING SST GRADIENT ALONG THE DIRECTION OF
MOTION

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: TROPICAL STORM (TS) 06W (KHANUN) IS FORECAST
TO CONTINUE TRACKING GENERALLY EASTWARD OVER THE NEXT 36 HOURS
UNDER THE STEERING INFLUENCE OF THE NER TO THE SOUTH. AS TRACK
SPEEDS INCREASE, UPWELLING BECOMES MUCH LESS OF A FACTOR, THOUGH
LOW VERTICAL WIND SHEAR AND WARMING SSTS WILL STILL STRUGGLE TO
FUEL ANY SUBSTANTIAL INTENSIFICATION DUE IN PART TO THE SYSTEMS
LARGE RMW AND SHALLOW CORE CONVECTION. BY TAU 48, THE NER TO THE
SOUTH SHIFTS NORTHEASTWARD AND FORCES 06W TO EXECUTE A NORTHWARD
COURSE CHANGE. BETWEEN TAUS 48 AND 72, 06W IS FORECAST TO ONCE
AGAIN REACH TYPHOON STRENGTH AS IT APPROACHES SOUTHERN JAPAN. AS
THE SYSTEM MAKES LANDFALL, IT WILL QUICKLY TRAVERSE THE ISLAND OF
KYUSHU, PASSING ROUGHLY 75NM EAST OF SASEBO AND EVENTUALLY SPILLING
OUT INTO THE SEA OF JAPAN. BY TAU 120, THE SYSTEM WILL INTERACT
WITH A PASSING 500MB TROUGH AND ASSOCIATED BAROCLINIC ZONE WHICH
WILL INITIATE EXTRA-TROPICAL TRANSITION (ETT), WHILE AT THE SAME
TIME PROVIDING A ROBUST OUTFLOW CHANNEL. THIS ENHANCED OUTFLOW,
WHEN COMBINED WITH WARM SSTS MAY PROLONG OR SLIGHTLY ENHANCE THE
DURATION OF STORM FORCE WINDS, WHILE AT THE SAME TIME DELAYING THE
EXTRA-TROPICAL TRANSITION.

MODEL DISCUSSION: WITH THE EXCEPTION OF A FEW TROUBLE MAKERS TO
EITHER SIDE OF THE MULTI-MODEL CONSENSUS, THE BULK OF THE MODEL
GUIDANCE IS IN GOOD AGREEMENT. NVGM AND COAMPS-TC (NVGM VERSION)
REPRESENT THE EXTREME EASTWARD TRACK FORECASTS, WHILE UK-MET
ENSEMBLE IS THE LONE MEMBER TO THE FAR WEST. THE BULK OF THE MODELS
TRACK EASTWARD THROUGH TAUS 36-48 AFTERWARDS MAKING A SHARP
NORTHWARD TURN THROUGH THE FORECAST PERIOD. BASED ON THE PERSISTENT
CROSS TRACK SPREADING, THE JTWC TRACK FORECAST IS PLACED WITH
OVERALL MEDIUM CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE IS IN
FAIR AGREEMENT THROUGH THE FORECAST PERIOD WITH A 15KT SPREAD IN
SOLUTIONS BY TAU 120. SIMILAR TO THE TRACK FORECAST, BASED ON THE
PERSISTENT SPREAD IN INTENSITY GUIDANCE, THE JTWC INTENSITY
FORECAST IS PLACED WITH OVERALL MEDIUM CONFIDENCE.

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