WDPN31 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 03W (GUCHOL) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0N 130.9E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 319 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FAIRLY
DRAMATICALLY CHANGED STRUCTURE FROM JUST 12 HOURS AGO, WITH
NORTHWESTERLY SHEAR NOW STARTING TO MAKE ITS PRESENCE KNOWN. THE
EYE WHICH WAS SO FIRMLY IN PLACE YESTERDAY IS NOW COMPLETELY GONE
IN THE EIR, AND THE CENTRAL DENSE OVERCAST (CDO) HAS BECOME
INCREASINGLY RAGGED AND ASYMMETRIC. THE OUTER LOW-LEVEL CLOUD BANDS
ARE NOW CLEARLY EVIDENT IN THE SHORTWAVE INFRARED ON THE WESTERN
SIDE OF THE SYSTEM, AS DRY AIR AND CONVERGENT FLOW ALOFT CONTINUE
TO ERODE THE WESTERN SIDE OF THE CONVECTIVE STRUCTURE. A TIMELY
101645Z AMSR2 36GHZ IMAGE DEPICTED A SOLID MICROWAVE EYE FEATURE
AND WEAK CONVECTIVE BANDS TO THE NORTHWEST SIDE OF THE EYE AND
PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION TO THE WEST OF THE
AGENCY FIX POSITIONS. THE INITIAL INTENSITY IS LOWERED SLIGHTLY TO
80 KNOTS, FOR WHILE THE CONVECTION IS RAPIDLY FALLING APART, IT
WILL TAKE SOME TIME FOR THE WINDS TO SPIN-DOWN. ADDITIONALLY, A
100920Z RCM-2 SAR PASS SHOWED A VMAX OF AROUND 90 KNOTS WHICH
PROVIDES A GOOD CONFIRMED STARTING POINT FOR THE INTENSITY
ANALYSIS. THUS, THE INTENSITY IS HELD A BIT HIGHER THAN THE
OBJECTIVE ESTIMATES AND MORE IN LINE WITH THE DVORAK CURRENT
INTENSITY (CI) VALUES AND THE DMINT ESTIMATE USING THE AMSR2 OF 73
KNOTS. THE SYSTEM HAS PICKED UP SPEED, NOW MOVING NORTHEASTWARD
ALONG THE NORTHWEST SIDE OF THE NEAR EQUATORIAL RIDGE (NER) TO THE
SOUTHEAST. AS EVIDENCED BY THE DEGRADED STRUCTURE, THE ENVIRONMENT
IS BECOMING INCREASINGLY HOSTILE WITH MODERATE TO HIGH NORTHERLY
SHEAR, DECREASING OUTFLOW INTO THE FILLING TUTT CELL TO THE
NORTHEAST AND INFLUX OF DRY MID-LEVEL AIR AND CONVERGENT FLOW FROM
THE NORTH.

INITIAL WIND RADII BASIS: SCATTEROMETER AND SAR DATA.  

CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF A DEEP NER TO
THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 92 KTS AT 101420Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: DRY MID-LEVEL AIR AND CONVERGENT FLOW FROM THE
NORTH. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THE PRIMARY STEERING INFLUENCE HAS NOW SHIFTED
TO THE NER TO THE SOUTHEAST AND THIS OVERALL STEERING PATTERN IS
EXPECTED TO MAINTAIN FOR ANOTHER 24 TO 36 HOURS. AFTER THAT, AS THE
TUTT CELL TO THE EAST FILLS, THE PRIMARY STEERING MECHANISM WILL
SHIFT TO THE STR CENTERED NEAR 25N 155E. REGARDLESS, DUE TO THE
SHAPE OF THE UPPER-LEVEL PATTERN, THE TRACK OF TY 03W IS NOT
FORECAST TO SHOW MUCH VARIANCE AND WILL FOLLOW A GENERAL
NORTHEASTWARD TRACK THROUGH THE ENTIRE FORECAST PERIOD. PERSISTENT
NORTHERLY SHEAR, DECREASING SSTS AND MID-LEVEL DRY AIR INFLOW FROM
THE NORTH WILL COMBINE TO STEADILY WEAKEN THE SYSTEM THROUGH THE
NEXT 36 HOURS. AFTER TAU 36, THE SYSTEM WILL CROSS NORTH OF THE 26C
ISOTHERM AND WESTERLY SHEAR IS EXPECTED TO INCREASE DRAMATICALLY,
WHICH WILL DECAPITATE THE SYSTEM, LEAVING BEHIND A SHALLOW VORTEX
AND MARKING THE BEGINNING OF A VERY BRIEF TRANSITION TO A
SUBTROPICAL PHASE OF THE CYCLONE. BY TAU 72, THE SYSTEM WILL BE 50
KNOTS OR MORE OF SHEAR AS IT RACES NORTH INTO COOL OCEAN WATERS AND
STARTS EXTRATROPICAL TRANSITION (ETT) AS IT STARTS TO INTERACT WITH
A 500MB SHORTWAVE TROUGH MOVING EAST OVER JAPAN AND COMES UNDER THE
INFLUENCE OF A STRONG 200MB JET MAX. THE SYSTEM WILL COMPLETE ETT
NO LATER THAN TAU 72 AS A GALE FORCE LOW PRESSURE SYSTEM 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE MEAN TRACK GUIDANCE IS
VERY GOOD AGREEMENT THROUGH THE DURATION OF THE FORECAST, WITH
MINIMAL CROSS- OR ALONG-TRACK SPREAD. INTENSITY GUIDANCE IS ALSO IN
GOOD AGREEMENT ON A STEADY WEAKENING TREND THROUGH THE FORECAST
PERIOD, PROVIDING HIGH CONFIDENCE TO THE OVERALL JTWC FORECAST. 

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