WDPN31 PGTW 100300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 03W (GUCHOL) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.0N 129.9E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 465 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT TY 03W
HAS LIKELY PEAKED AND IS NOW STARTING TO FEEL THE EFFECTS OF
ENHANCED AND PERSISTENT NORTHERLY SHEAR. DEEP CONVECTION, WHICH
EARLIER HAD COMPLETELY SURROUNDED A FAIRLY CLEAR EYE FEATURE, HAS
NOW DISSIPATED AND THOUGH SOME CONVECTION IS ONCE MORE FLARING ON
THE SOUTHEAST SIDE OF THE SYSTEM, THE WESTERN SIDE OF THE NOW
CLOUD-FILLED AND RAGGED EYE IS NEARLY DEVOID OF DEEP CONVECTION. A
092143Z SSMIS 91GHZ IMAGE REVEALED THAT THE NORTHWEST SIDE OF THE
EYEWALL IS PREDOMINANTLY OPEN, WITH ONLY LOW-LEVEL BANDING FEATURES
EVIDENT IN THE MICROWAVE IMAGERY, WHILE THE SOUTHEASTERN FLANK
CONTINUES TO EXHIBIT STRONG CONVECTIVE ACTIVITY. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE RAGGED,
ROUGHLY 30NM WIDE EYE FEATURE IN THE VISIBLE IMAGERY. BASED ON
ANALYSIS OF HOURLY DPRINT AND 30MIN ADT ESTIMATES, THE SYSTEM
APPEARS TO HAVE PEAKED AT 95 KNOTS AT APPROXIMATELY 2100Z BUT NOW
IS STARTING TO TREND DOWNWARDS ONCE MORE. THE INITIAL INTENSITY IS
ASSESSED AT 90 KNOTS WITH MEDIUM CONFIDENCE, IN LINE WITH ALL
REPORTING AGENCIES. ADT IS REPORTING A RELATIVELY HIGH T5.5, THOUGH
THE RAW VALUES ARE DOWN TO THE T4.0 RANGE, INDICATIVE OF THE RECENT
WEAKENING TREND. THE SYSTEM CONTINUES TO DRIFT SLOWLY NORTHWARD IN
A RELATIVELY WEAK STEERING PATTERN. ANALYSIS INDICATES THE
ENVIRONMENT, WHILE STILL GENERALLY FAVORABLE, IS BECOMING LESS SO,
WITH THE SHEAR STARTING TO EXERT AN INCREASINGLY NEGATIVE IMPACT,
OFFSETTING THE WARM SSTS AND GOOD EASTWARD AND EQUATORWARD OUTFLOW.
SOUNDINGS FROM MINAMI DAITO JIMA CONTINUE TO SHOW A MODERATELY DEEP
LAYER OF VERY DRY AIR BETWEEN 700-400MB, WHICH IS STARTING TO BE
ADVECTED TO THE SOUTH ALONG THE WESTERN SIDE OF THE SYSTEM.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN, WITH A NEAR
EQUATORIAL RIDGE (NER) TO THE SOUTHEAST, A SUBTROPICAL RIDGE (STR)
TO THE NORTHEAST AND A DEEP-LAYER TUTT CELL DUE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 102 KTS AT 092330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: WEAK TO MODERATE EQUATORWARD OUTFLOW; MID-LEVEL
DRY AIR TO THE NORTH.

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 03W IS WOBBLING IN A GENERAL NORTHWARD
DIRECTION AS IT WORKS IT WAITS FOR THE WEAK STEERING ENVIRONMENT TO
FIRM UP. THE RELATIVELY DEEP TUTT CELL LURKING OUT TO THE EAST IS
ANTICIPATED TO CONTINUE MOVING TO THE NORTHWEST AND FILL, WHILE THE
NER TO THE SOUTH WILL PUSH UP FROM THE NORTH AND ULTIMATELY MERGE
WITH THE STR TO THE NORTHEAST, FORMING ONE LARGE RIDGE COMPLEX
LYING ALONG A ROUGH SOUTHWEST TO NORTHEAST AXIS. THIS PROCESS IS
EXPECTED TO BE COMPLETE BY TAU 24 AND TY 03W WILL START TO PICK UP
THE PACE OVER THE NEXT 12 TO 24 HOURS AS IT BEGINS TO TURN OVER TO
A MORE NORTHEASTWARD HEADING. BY TAU 24, THE SYSTEM WILL BE FIRMLY
TRACKING TO THE NORTHEAST AND WILL STEADILY ACCELERATE THROUGH THE
REMAINDER OF THE FORECAST PERIOD AS THE TIGHTENING STEERING
GRADIENT ON THE WEST SIDE OF THE BUILDING RIDGE COMPLEX TO THE
EAST. TY 03W HAS LIKELY REACHED ITS PEAK AND THE IMPACT OF THE
INCREASING WEST-NORTHWEST SHEAR, DECREASING SSTS AND THE DRY AIR
AWAITING IT TO THE NORTH, WILL LEAD TO A STEADY WEAKENING OF THE
SYSTEM THROUGH TAU 48. AT THAT POINT AS THE SYSTEM PASSES NORTH OF
THE 26C ISOTHERM AND BEGINS TO INTERACT WITH A WEAK 500MB SHORTWAVE
TROUGH, IT WILL BEGIN SUBTROPICAL TRANSITION (STT), WITH FULL
TRANSITION TO A STORM-FORCE SUBTROPICAL LOW EXPECTED NO LATER THAN
TAU 60 AS IT PASSES THE 30N LATITUDE. THEREAFTER, THE SYSTEM BEGINS
THE PHASE TRANSITION TO A WARM-CORE EXTRATROPICAL LOW AS IT
DEVELOPS FRONTAL CHARACTERISTICS AND MOVES UNDER A FINGER OF THE
POLAR FRONT JET AND RACES FURTHER INTO THE NORTH PACIFIC. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
VERY GOOD AGREEMENT THROUGH TAU 72, WITH MINIMAL CROSS OR
ALONG-TRACK SPREAD. AS THE SYSTEM UNDERGOES ETT AFTER TAU 72, MODEL
GUIDANCE BEGINS TO DIVERGE, WITH SPREAD INCREASING TO 175NM
CROSS-TRACK AND 300NM ALONG-TRACK. THE JTWC FORECAST LIES JUST
INSIDE THE MULTI-MODEL CONSENSUS THROUGH THE FORECAST, WITH HIGH
CONFIDENCE TO TAU 72, AND MEDIUM CONFIDENCE THROUGH THE END OF THE
FORECAST. INTENSITY GUIDANCE IS IN GOOD AGREEMENT, WITH ALL
CONSENSUS MEMBERS INDICATING SLOW WEAKENING THROUGH TAU 48,
FOLLOWED BY MORE RAPID WEAKENING THROUGH THE END OF THE FORECAST,
LENDING HIGH CONFIDENCE TO THE JTWC FORECAST.  

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