WDPN32 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (KHANUN) WARNING NR 
036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.7N 126.9E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 87 NM NORTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: EASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY LOOP INDICATES THERE HAS
BEEN LITTLE CHANGE IN THE APPEARANCE OF TS 06W OVER THE PAST SIX
HOURS, WITH TIGHTLY-CURVED BANDING CONTINUING TO WRAP INTO A
DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) OF THIS BROAD SYSTEM. A
042136Z RCM-3 SAR PASS REVEALS A BROAD SWATH OF 50 TO 55 KNOT OCEAN
SURFACE WINDS APPROXIMATELY 50 NM FROM THE LLCC, WITH A FEW PIXELS
OF POTENTIAL 60 KNOT VALUES. THE OUTER WIND FIELD EXTENT OF 06W WAS
TOO LARGE TO FIT WITHIN THE EXTRA-WIDE SENSOR SWATH, BUT THE DATA
PROVIDES GOOD ESTIMATES TO UPDATE THE R34 AND R50 VALUES. THE RAW
SAR RADAR RETURNS ALONG WITH MULTI-AGENCY FIX AGREEMENT PROVIDES
GOOD CONFIDENCE FOR THE ANALYZED INITIAL POSITION, WHICH INDICATES
TS 06W IS TRACKING ALMOST DUE EAST UNDER THE STEERING INFLUENCE OF
A NEAR EQUATORIAL RIDGE (NER) ANCHORED OVER THE CENTRAL
PHILIPPINES. PEAK 10 MIN WIND MEASUREMENTS OBSERVED FROM REPORTING
STATIONS IN THE AREA ARE BETWEEN 40 TO 45 KNOTS. THE INITIAL
INTENSITY WAS HELD AT 55 KNOTS BASED ON THE SAR DATA, WITH
AGREEMENT BY THE RJTD CURRENT INTENSITY T3.5 VALUE, AS WELL AS
DMINT, DPRINT, AND SATCON ESTIMATES. ENVIRONMENTAL CONDITIONS
ARE MARGINALLY FAVORABLE DUE PRIMARILY TO THE UPWELLING OF 22-24 
DEGREE WATERS IN KHANUNS WAKE, BUT VALUES ARE INCREASING ALONG THE
DIRECTION OF MOTION. KHANUN HAS MANAGED TO MAINTAIN ITS INTENSITY
LARGELY THANKS TO GOOD OUTFLOW INTO A UPPER LEVEL SUB-TROPICAL LOW
TO THE NORTHEAST AND LOW VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: SAR DATA

CURRENT STEERING MECHANISM: NER TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 58 KTS AT 042010Z
   CIMSS ADT: 32 KTS AT 042330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 26-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: UPPER-LEVEL LOW TO THE EAST ENHANCING OUTFLOW, 
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 IS EXPECTED TO
CONTINUE A PREDOMINANTLY EASTWARD MOTION WITHIN THE NER FLOW OVER
THE NEXT 36 HOURS. DURING THIS TIME, HWRF FIELDS INDICATE KHANUN WILL 
MAINTAIN ITS LARGE RADIUS OF MAXIMUM WINDS AND SHALLOW CORE 
CONVECTION. AFTER TAU 36, RIDGING WILL BUILD AND REORIENT TO A MORE 
ZONAL AXIS AHEAD OF THE TRACK RESULTING IN A POLEWARD TURN. WARMER 
WATERS WILL HELP DRIVE A SHORT PERIOD OF RE-INTENSIFICATION PRIOR TO 
LANDFALL, WITH HFWF SUGGESTING A BRIEF RETURN TO TYPHOON INTENSITY 
NEAR TAU 72 AHEAD OF LANDFALL. ONCE OVER KYUSHU, A 500MB SHORTWAVE 
TROUGH SHOULD CAPTURE THE SYSTEM, FURTHER ENHANCING THE POLEWARD 
MOTION AND BEGINNING AN EXTRATROPICAL TRANSITION PHASE. HOWEVER, WARM 
27 DEGREE C WATERS OVER THE SEA OF JAPAN MAY PROLONG THE TRANSITION
AND HELP MAINTAIN STORM FORCE WINDS THROUGHOUT THE REMAINDER OF THE
FORECAST PERIOD. THE FORECAST TRACK WAS PLACED VERY CLOSE TO THE
PRIOR FORECAST. 

MODEL DISCUSSION: MULTI-MODEL CONSENSUS AGREEMENT IS GOOD THROUGH
TAU 48, AFTER WHICH TWO MEMBERS BECOME OUTLIERS, NAVGEM TO THE EAST
AND UKMET ENSEMBLE MEAN TO THE WEST. HOWEVER, THE REMAINING MEMBERS
ALL TRACK OVER KYUSHU. THE 18Z OFF-CYCLE ECMWF RUN HOWEVER IS
MAKING A SHARPER TURN PASSING OFF THE WEST OF KYUSHU AT TAU 96.
STANDING BY TO SEE IF THIS TREND CONTINUES IN THE 00Z RUN.
INTENSITY GUIDANCE IS IN MODERATE AGREEMENT, WITH STEADY STATE
UNTIL JUST PRIOR TO LANDFALL WHEN A SHORT RE-INTENSIFICATION
OCCURS. 

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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