WDPN31 PGTW 252100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (CHAMPI) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.7N 139.7E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 110 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION OVERHEAD THE LOW LEVEL CIRCULATION CENTER (LLCC) WITH
BANDING WRAPPING AROUND FROM THE NORTHWEST. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON TURNING IN THE EIR IMAGERY
ALONG WITH A 251830Z GMI 89 GHZ MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 65 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON
MULTI-AGENCY DVORAK INTENSITY ESTIMATES. HIGH RESOLUTION MODEL
CROSS SECTIONS INDICATE MID-LEVEL DRY AIR IMPINGING FROM BOTH THE 
EAST AND WEST, LIKELY INHIBITING THE CONTINUED CONSOLIDATION OF A 
CONVECTIVE CORE.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP LAYER SUBTROPICAL RIDGE (STR) TO
THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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: TY 06W HAS CRESTED THE STR AXIS AND IS
EXPECTED TO TRACK NORTH-NORTHEAST THROUGH TAU 36 BEFORE TURNING TO
A NORTHEASTWARD TRACK FOR THE REMAINDER OF THE FORECAST PERIOD. IN
THE NEAR TERM, THE SYSTEM MAY CONTINUE TO INTENSIFY TO A PEAK OF 75
KTS BY TAU 12. HOWEVER, THE PEAK INTENSITY MAY BE LOWER IF THE 
SYSTEM CANNOT MAINTAIN THE CONVECTIVE CORE. AFTERWARDS, PASSAGE OF A 
SHORTWAVE TROUGH OVER THE SYSTEM WILL INTRODUCE CONVERGENT FLOW 
ALOFT, INCREASE VERTICAL WIND SHEAR VALUES, AND LEAD TO A STEADY 
WEAKENING OF TY 06W. BY TAU 36, SEA SURFACE TEMPERATURES WILL DROP 
BELOW 26 CELSIUS CAUSING THE SYSTEM TO FURTHER WEAKEN. CONCURRENTLY, 
TY 06W WILL START EXTRATROPICAL TRANSITION AS IT INTERACTS WITH THE 
BAIU BOUNDARY AND ACCELERATES TO THE NORTHEAST. ALONG THIS TRACK, TY 
06W WILL BECOME EMBEDDED WITHIN THE BAROCLINIC ZONE AND MOVE UNDER 
THE 200MB JET FLOW. EXTRATROPICAL TRANSITION COMPLETION IS EXPECTED 
BY TAU 72, IF NOT SOONER.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
WITH ONLY A 60 NM ACROSS-TRACK SPREAD BY TAU 48. THE JTWC FORECAST 
IS PLACED NEAR THE MULTI-MODEL CONSENSUS AND IS IN GOOD AGREEMENT 
WITH THE ECMWF MODEL SOLUTION. GALWEM IS THE ONE WESTERLY OUTLIER 
THROUGHOUT THE FULL FORECAST PERIOD. AS THE SYSTEM ACCELERATES 
NORTHEASTWARD DURING EXTRATROPICAL TRANSITION, ALONG-TRACK SPREAD 
BEGINS TO INCREASE TO A MAXIMUM OF 203 NM BY TAU 72. THE JTWC
INTENSITY FORECAST IS SLIGHTLY LOWER THAN THE PREVIOUS FORECAST AND
ALIGNED WITH CURRENT MODEL GUIDANCE. WITH THE LIMITED PERIOD OF
FAVORABLE CONDITIONS REMAINING, MODEL GUIDANCE SHOWS A BRIEF PERIOD
OF INTENSIFICATION PRIOR TO A STEADY WEAKENING TREND. THE PEAK
INTENSITY HAS DECREASED FROM THE PREVIOUS FORECAST. 

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