WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 03W (GUCHOL) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.2N 130.4E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 576 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 29 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAGGED
30-40 NM DIAMETER EYE SURROUNDED BY CLOUD TOPS THAT HAVE WARMED A
BIT OVER THE PAST 6 HOURS, WITH LARGER GAPS APPEARING IN THE
EYEWALL. AN 082157Z SSMIS MICROWAVE PASS CONFIRMED THAT THE WESTERN
EYEWALL WAS OPEN AGAIN, WITH ONLY ABOUT TWO THIRDS AZIMUTHAL
CLOSURE. TYPHOON GUCHOL IS NOW OVER THE COLD WAKE LEFT BEHIND BY
TYPHOON MAWAR ABOUT 10 DAYS AGO, WHICH MAY BE CONTRIBUTING TO
EYEWALL DEGRADATION. ENVIRONMENTAL DRY, STABLE AIR TO THE NORTHWEST
MAY ALSO BE GETTING ENTRAINED INTO THE NORTHWEST QUADRANT NOW. THE
INITIAL INTENSITY IS HELD AT 80 KT BASED ON THE AVERAGE OF AGENCY
DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   CIMSS ADT: 102 KTS AT 082330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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 03W (GUCHOL) IS IN THE PROCESS OF
MAKING A SLOW TURN NORTHWARD AROUND THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE TO ITS NORTHEAST. A NORTHEASTWARD HEADING AND
ACCELERATING FORWARD MOTION IS EXPECTED AFTER 36 HOURS AS GUCHOL
APPROACHES THE MID-LATITUDE WESTERLIES. IN THE SHORT TERM, THE
NORTHWESTWARD TO NORTHWARD TRACK IS TAKING GUCHOL OVER THE COLD
WAKE LEFT BEHIND BY TYPHOON MAWAR 10 DAYS AGO, WHICH IS LIKELY TO
PUT A CEILING ON ITS INTENSITY. SOME INTENSIFICATION IS POSSIBLE
DURING THE NEXT 12 HOURS, AND THE JTWC FORECAST SHOWS A PEAK 
INTENSITY OF 85 KT, A LITTLE LOWER THAN THE PREVIOUS FORECAST. AFTER 
12-24 HOURS, MARGINAL OCEANIC CONDITIONS AND MODERATE VERTICAL WIND 
SHEAR ARE LIKELY TO INDUCE GRADUAL WEAKENING. AFTER 72 HOURS, GUCHOL 
WILL PASS OVER WATERS COLDER THAN 26 DEGREES CELSIUS, AND IS EXPECTED 
TO TRANSITION INTO A SUBTROPICAL CYCLONE BY 120 HOURS AS IT CONTINUES 
TO TRACK SOUTH OF THE MID-LATITUDE JET STREAM IN A REGION OF LIMITED 
BAROCLINICITY.


MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT
THROUGH 72 HOURS, AND HAS TIGHTENED IN THE 72-120 HOUR RANGE SINCE 
THE PREVIOUS FORECAST. CONFIDENCE IS GENERALLY HIGH IN THIS FORECAST,
THOUGH SOME UNCERTAINTY REMAINS BEYOND 72 HOURS AS GUCHOL
APPROACHES THE MID-LATITUDE JET IN A WAY THAT MAKES ITS EXACT
FORWARD SPEED A LITTLE UNCERTAIN. THE JTWC FORECAST IS SLIGHTLY TO
THE RIGHT OF THE MULTI-MODEL CONSENSUS, CLOSER TO THE ECMWF, GFS,
AND GFS ENSEMBLE GROUPING OF MODELS. THE JTWC INTENSITY FORECAST
IS CLOSE TO THE MULTI-MODEL CONSENSUS THROUGHOUT THE FORECAST PERIOD.

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