WDPN32 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (KHANUN) WARNING NR 027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.5N 125.0E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 150 NM WEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
CONTRACTING INNER EYE WITH COOLING CENTRAL BRIGHTNESS TEMPERATURE
OVER THE PAST SIX HOURS, WITH A MAINTAINING COLD RING SYMMETRICALLY
SURROUNDING THE EYE. RADAR IMAGERY FROM JAPAN INDICATES THAT THE
INNER EYEWALL REMAINS INTACT AT ABOUT 15 NM DIAMETER, WITH A MOSTLY
COMPLETE OUTER CONCENTRIC BAND AROUND THE INNER EYEWALL WITH A
DIAMETER OF ABOUT 100 NM. GALE FORCE WINDS EXTEND DOWN SOUTH OF 
MIYAKOJIMA, WHERE SUSTAINED WINDS AS HIGH AS 47 KTS HAVE BEEN 
OBSERVED IN THE PAST FEW HOURS. GALE FORCE WINDS HAVE ALSO BEEN 
OBSERVED ON OKINAWA IN RECENT HOURS TO THE EAST OF THE TYPHOON'S 
CORE. THE INITIAL POSITION IS BASED ON RADAR AND SATELLITE DATA, AND 
THE INITIAL INTENSITY OF 100 KTS IS BASED ON A BLEND OF OBJECTIVE AND 
SUBJECTIVE SATELLITE ESTIMATES RANGING FROM ABOUT 90 KT TO 110 KT.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SAR DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 104 KTS AT 021730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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 06W (KHANUN) IS MOVING INTO THE EAST
CHINA SEA AND IS LIKELY ABOUT TO BEGIN THE DECAY PROCESS DUE TO
COLD UPWELLING CAUSED BY ITS SLOW FORWARD MOTION. THE FIRST
EVIDENCE OF THIS DECAY MAY BE THE CONTRACTION AND WARMING OF THE
EYE IN INFRARED SATELLITE IMAGERY IN RECENT HOURS. GRADUAL
WEAKENING IS LIKELY TO CONTINUE THROUGH 48-72 HOURS AS THE TYPHOON
MOVES WEST-NORTHWESTWARD AND THEN STALLS BEFORE TURNING BACK
EAST-NORTHEASTWARD, A TRACK THAT WILL RESULT IN SIGNIFICANT OCEAN
COOLING BENEATH THE STORM'S CORE. THIS STALL AND TURN BACK EASTWARD
WILL BE CAUSED BY A COMBINATION OF A WEAKENING SUBTROPICAL RIDGE
OVER KOREA TO THE NORTH OF THE TYPHOON AND A STRENGTHENING
MONSOONAL BELT OF SOUTHWESTERLIES MIGRATING CLOSER TO THE TYPHOON
ON ITS SOUTH SIDE. NUMERICAL MODELS ARE IN GOOD AGREEMENT ON THIS
TURN BACK TOWARDS THE RYUKYU ISLANDS, AND THE JTWC TRACK FORECAST
CROSSES AMAMI OSHIMA BETWEEN 72 AND 96 HOURS. THEREAFTER, A TURN
TOWARDS MAINLAND JAPAN MAY OCCUR AS THE TYPHOON BUTTS UP AGAINST
THE SUBTROPICAL RIDGE EAST OF JAPAN. HOWEVER, THERE IS SIGNIFICANT
MODEL SPREAD IN THE TYPHOON'S FORWARD SPEED DURING THIS TIME, OWING
TO WEAK STEERING CURRENTS AND UNCERTAINTY IN THE DEVELOPMENT OF
SEVERAL STEERING FEATURES, INCLUDING SHORTWAVE TROUGHS SWINGING
THROUGH KOREA DURING THE 72-120 HOURS PERIOD, AS WELL AS THE
POTENTIAL DEVELOPMENT OF A NEW CYCLONE SOUTHEAST OF HONSHU, WHICH
COULD IMPACT STEERING FOR 06W IF THAT OCCURS. THE JTWC TRACK
FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS AND SHIFTED ONLY
SLIGHTLY NORTH OF THE PREVIOUS FORECAST, AND SLIGHTLY FASTER.
OVERALL CONFIDENCE IN THE 72-120 HOUR TRACK FORECAST IS LOWER THAN
AVERAGE. REGARDING INTENSITY, KHANUN MAY DIP BELOW TYPHOON STRENGTH
DUE TO COLD UPWELLING AS IT MEANDERS THROUGH THE EAST CHINA SEA,
BUT ITS EAST-NORTHEASTWARD MOTION DURING THE 72-120 HOUR PERIOD
WOULD BRING IT OVER WARMER WATERS AGAIN. FOR NOW, THE JTWC
INTENSITY FORECAST IS ONLY FOR SLIGHT REINTENSIFICATION AT THE END
OF THE FORECAST PERIOD DUE TO THE LIKELY BROAD NATURE OF THE
TYPHOON'S CORE FOLLOWING THE DEGRADATION OF THE INNER CORE THAT IS
EXPECTED OVER THE COLD WATER OVER THE NEXT 72 HOURS, WHICH WOULD
NOT FAVOR QUICK REINTENSIFICATION.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO AND SLIGHTLY
SLOWER THAN THE MULTI-MODEL CONSENSUS. THE JTWC INTENSITY FORECAST
IS SLIGHTLY LOWER THAN THE MULTI-MODEL CONSENSUS, PLACING LESS
WEIGHT ON MODELS WHICH ARE NOT DYNAMICALLY COUPLED TO THE OCEAN,
AND THUS DO NOT SEE THE COLD UPWELLING THAT WILL OCCUR BENEATH THE
TYPHOON.

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