WDPN31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (CHAMPI) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 139.2E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 199 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL AND ENHANCED INFRARED IMAGERY SHOWS THAT
OVERALL CONVECTIVE ACTIVITY HAS WANED AND CLOUD TOPS HAVE WARMED
OVER THE PAST SIX HOURS. HOWEVER, BY THE 0600Z HOUR, NUMEROUS
VORTICAL HOT TOWERS (VHT) WERE OBSERVED TO BE RAPIDLY DEVELOPING IN
AND AROUND THE CORE OF THE SYSTEM, PARTICULARLY ON THE SOUTHEAST
AND WESTERN PERIPHERY, POTENTIALLY INDICATIVE OF A NEW ROUND OF
INTENSIFICATION. UPPER-LEVEL WATER VAPOR IMAGERY, AND CIMMS
ANALYSIS SHOWS SOME FAIRLY STRONG EASTERLY ENVIRONMENTAL FLOW TO
THE EAST OF THE SYSTEM, WHICH IS INHIBITING DEVELOPMENT ON THAT
SIDE OF THE SYSTEM. A 250510Z GMI 89 GHZ MICROWAVE IMAGE CONFIRMED
THE INITIAL POSITION, AND ALSO SHOWED THAT WHILE THE MSI DEPICTION
IS FAIRLY IMPRESSIVE, THE INNER CORE HAS YET TO COMPLETELY FORM,
WITH A DISTINCT LACK OF CONVECTIVE ACTIVITY ON THE EASTERN SIDE OF
THE CORE, AS INDICATED BY THE WATER VAPOR IMAGERY. THE CURRENT
INTENSITY IS INCREASED TO TYPHOON STRENGTH (65 KTS) IN LINE WITH
THE MAJORITY OF DVORAK SUBJECTIVE INTENSITY ESTIMATES. THE OVERALL
ENVIRONMENT CONTINUES TO IMPROVE, WITH THE STRONG EQUATORWARD
OUTFLOW BEING COMPLIMENTED BY A WEAK BUT QUICKLY IMPROVING POLEWARD
OUTFLOW CHANNEL INTO STRONG MID-LATITUDE WESTERLIES. VERTICAL WIND 
SHEAR (VWS) REMAINS LOW AND SEA SURFACE TEMPERATURES (SSTS) REMAIN 
ABOVE 28C, LENDING ADDITIONAL FUEL FOR FURTHER INTENSIFICATION.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK. 

CURRENT STEERING MECHANISM: DEEP SUBTROPICAL RIDGE (STR) CENTERED
TO THE EAST-NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 59 KTS AT 250339Z
   CIMSS ADT: 59 KTS AT 250540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: POLEWARD OUTFLOW CURRENTLY WEAK TO MODERATE, BUT
IS RAPIDLY IMPROVING.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON CHAMPI IS FORECAST TO CONTINUE
TRACKING NORTHWARD OVER THE NEXT 12 HOURS, SLOWING SLIGHTLY AS IT
APPROACHES THE AXIS OF THE STEERING STR. IT IS EXPECTED TO ROUND
THE AXIS OF THE RIDGE BY TAU 24 AND THEN ACCELERATE NORTHEASTWARD
THROUGH THE REMAINDER OF THE FORECAST PERIOD. OVERALL ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO CONTINUE TO IMPROVE THROUGH TAU 24, WITH
VWS REMAINING LOW, AND POLEWARD OUTFLOW INCREASING, ALLOWING FOR A
PERIOD OF NEAR-RAPID INTENSIFICATION, REACHING A PEAK OF 90 KTS BY
TAU 24. BEYOND TAU 24, FIRST SLOW, THEN RAPID WEAKENING IS EXPECTED
AS THE SYSTEM MOVES OVER COOLER WATERS (LESS THAN 26C) AND
ENCOUNTERS RAPIDLY INCREASING VWS AS IT MOVES STEADILY CLOSER TO
THE BAIU BOUNDARY TO THE SOUTHEAST OF HONSHU. BY TAU 48, THE
INTERACTION WITH THE BAIU WILL BEGIN, AND THE SYSTEM WILL MOVE
UNDER THE NOSE OF A 200MB JET MAX, INDUCING EXTRATROPICAL
TRANSITION (ETT), WHICH IS EXPECTED TO BE COMPLETE NO LATER THAN
TAU 72, BUT LIKELY BY TAU 60. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 48, WITH ONLY A 60 NM SPREAD, WITH INCREASING
ALONG-TRACK UNCERTAINTY BY TAU 72, LENDING MEDIUM CONFIDENCE TO THE
FORECAST TRACK. THE JTWC FORECAST LIES CLOSE TO THE MULTI-MODEL
CONSENSUS THROUGH TAU 24, THEN ON THE RIGHT SIDE OF THE ENVELOPE
AND SLIGHTLY FASTER THAN THE CONSENSUS MEAN THROUGH THE REMAINDER
OF THE FORECAST. IN TERMS OF INTENSITY, THE RAPID INTENSIFICATION
PREDICTION AID (RIPA) IS PREDICTING A 60 PERCENT PROBABILITY OF
RAPID INTENSIFICATION THROUGH TAU 24, WHILE THE HWRF SOLUTION HAS
BACKED OFF SLIGHTLY WITH THE LATEST RUN. THE JTWC FORECAST LIES
ABOVE THE CONSENSUS MEMBERS IN LINE WITH THE HIGH RIPA
PROBABILITIES. BUT DUE TO THE COMPACT NATURE OF THE SYSTEM, AND THE
SHORT-CYCLING IN INTENSITY WITNESSED OVER THE PREVIOUS FEW DAYS,
THERE IS ONLY MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST. 

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