WDPN31 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (CHAMPI) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.8N 139.7E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 87 NM WEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION WITH CONVECTION OVER THE EASTERN
PERIPHERY AND THE CENTER. OVER THE PAST SEVERAL HOURS, CONVERGENT
FLOW ASSOCIATED WITH A SHORTWAVE TROUGH TO THE WEST OF THE SYSTEM
HAS ERODED THE CONVECTION OVER THE WESTERN PERIPHERY. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY
EXPOSED NATURE OF THE SYSTEM AND AN EXTRAPOLATION OF A 252152Z
SSMIS 91 GHZ MICROWAVE IMAGE SHOWING CONVECTION WRAPPING AROUND THE
SOUTHERN AND EASTERN PERIPHERIES. THE INITIAL INTENSITY OF 65 KTS
IS ASSESSED WITH HIGH CONFIDENCE BASED ON A CONSENSUS OF
MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES AND AN ADVANCED
DVORAK TECHNIQUE (ADT) ESTIMATE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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
   RCTP: T4.0 - 65 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 65 KTS AT 252330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 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 IS FORECAST TO TRACK
NORTH-NORTHEASTWARD THROUGH TAU 36. IN THE NEAR TERM, THE
MARGINALLY FAVORABLE ENVIRONMENT SHOULD ALLOW THE SYSTEM TO
MAINTAIN CURRENT INTENSITY THROUGH TAU 12. AFTERWARDS, AS VERTICAL
WIND SHEAR INCREASES AND SEA SURFACE TEMPERATURES BEGIN TO COOL, TY
06W SHOULD BEGIN TO EXPERIENCE A STEADY WEAKENING TREND. BY TAU 36,
THE SYSTEM WILL BEGIN TO INTERACT WITH THE BAIU BOUNDARY AND START
EXTRATROPICAL TRANSITION (ETT) AS IT ACCELERATES NORTHEASTWARD
THROUGH TAU 48. ETT COMPLETION IS EXPECTED BY TAU 48 AS THE SYSTEM
BECOMES EMBEDDED WITHIN THE BAROCLINIC ZONE AND MOVES UNDER THE JET
FLOW. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT WITH ACROSS-TRACK SPREAD INCREASING TO 110 NM BY TAU 48.
THE JTWC FORECAST TRACK IS PLACED NEAR THE MULTI-MODEL CONSENSUS.
AS THE SYSTEM ACCELERATES NORTHEASTWARD DURING EXTRATROPICAL 
TRANSITION, ALONG-TRACK SPREAD INCREASES TO 151 NM BY TAU 48. THE 
JTWC INTENSITY FORECAST IS IN GOOD AGREEMENT WITH MODEL SOLUTIONS 
WHICH SHOW A STEADY WEAKENING TREND AFTER TAU 12. HWRF REMAINS THE 
ONE EXCEPTION WHICH INDICATES A BRIEF INTENSIFICATION PERIOD THROUGH 
TAU 12.

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