WDPN31 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 03W (GUCHOL) WARNING NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.5N 129.9E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 494 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT THE
STRUCTURE OF TY 03W HAS STEADILY IMPROVED OVER THE PAST SIX HOURS,
WITH DEEP CONVECTION WITH COLD CLOUD TOPS NOW SURROUNDING THE BULK
OF THE 45NM WIDE EYE FEATURE. EYE TEMPERATURES ARE NOW APPROACHING
+8C, THOUGH CLOUD TOP TEMPERATURES ARE A MORE MODEST -63C. A
091714Z ATMS 183GHZ MICROWAVE IMAGE REVEALED A BROAD MICROWAVE EYE
FEATURE WITH A COMPLETELY CLOSED EYEWALL, AND THE STRONGEST
CONVECTION ALONG THE SOUTHERN PERIPHERY. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE EYE IN BOTH THE EIR AND
THE ATMS IMAGERY. A 090922Z RADARSAT-2 SAR PASS SHOWED MAXIMUM
WINDS OF 85 KNOTS, AND THE 12Z BEST TRACK WAS UPDATED TO REFLECT
THAT INTENSITY. THE INITIAL INTENSITY IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE AGREEMENT OF THE BULK OF THE REPORTING
AGENCIES AS WELL AS THE AIDT, DPRINT AND SATCON ESTIMATES. THE
SYSTEM IS MOVING SLOWLY NORTHWARD AT JUST 02 KNOTS ALONG THE
GENERAL WESTERN PERIPHERY OF A COMPLEX UPPER-LEVEL RIDGE PATTERN,
WITH A SUBTROPICAL RIDGE (STR) CENTERED NEAR 30N 155E AND A NEAR
EQUATORIAL RIDGE (NER) NEAR 10N 140E AND A STRONG TUTT-CELL
SANDWICHED IN BETWEEN, WHICH IS BREAKING UP THE RIDGE PATTERN
SOMEWHAT. THE RESULT IS THAT FOR THE MEANTIME THE FORWARD MOTION IS
VERY SLOW. THE ENVIRONMENT CONTINUES TO BE GENERALLY FAVORABLE,
CHARACTERIZED BY LOW (10-15 KTS) NORTHERLY VWS, WARM SSTS (AROUND
28C) AND GOOD EASTWARD OUTFLOW INTO THE TUTT CELL TO THE EAST AND
FAIR EQUATORWARD (SOUTHWESTWARD) OUTFLOW. ANIMATED WATER VAPOR
IMAGERY AS WELL AS THE LATEST SOUNDING FROM MINAMI DAITO JIMA
INDICATE THE PRESENCE OF VERY DRY MID-LEVEL AIR BELOW THE OUTFLOW
LAYER (ROUGHLY 400-700MB) LURKS TO THE NORTH.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN SIDE OF A LARGE, COMPLEX RIDGE
PATTERN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 84 KTS AT 091623Z
   CIMSS ADT: 99 KTS AT 091730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: WEAK EQUATORWARD OUTFLOW; DRY MID-LEVEL AIR TO
THE NORTH. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: OVER THE NEXT SIX HOURS OR SO, TY 03W IS
EXPECTED TO CONTINUE DRIFTING RATHER SLOWLY, GENERALLY TOWARDS THE
NORTH AS THE STEERING PATTERN REMAINS COMPLEX BUT CONTINUES TO
EVOLVE. GLOBAL MODELS AGREE THAT THE TUTT CELL WHICH IS CURRENTLY
DISRUPTING THE RIDGE PATTERN TO THE EAST, WILL SLOWLY FILL AND
CONTINUE MOVING WESTWARD, ALLOWING FOR THE NER TO THE SOUTH TO
SLIDE NORTHWARD AND MERGE WITH THE STR TO NORTHEAST. IN RESPONSE TO
THESE CHANGES IN THE UPPER-LEVEL PATTER, TY 03W WILL START TO PICK
UP SPEED AFTER TAU 12, THEN TURN NORTHEASTWARD BY TAU 24 AS THE
RIDGE PATTERN BECOMES MORE ROBUST. THE SYSTEM WILL THEN CONTINUE TO
STEADILY ACCELERATE ON A NORTHEASTWARD HEADING THROUGH THE
REMAINDER OF THE FORECAST PERIOD. EVEN IN THE FACE OF PERSISTENT,
MODERATE NORTHERLY SHEAR AND MARGINAL SSTS AND LIMITED OHC, TY 03W
HAS CONTINUED TO INTENSIFY SLIGHTLY, BASED ON REANALYSIS OF LAST
NIGHTS SAR PASS AND CURRENT INTENSITY ESTIMATES FROM ALL REPORTING
AGENCIES. THROUGH THE NEXT 12 HOURS, CONVECTION IS LIKELY TO
CONTINUE PULSING, PARTICULARLY AS CONVECTIVE MAXIMUM APPROACHES,
LEADING TO A STEADY INTENSITY THROUGH TAU 12. THEREAFTER, AN
EXPECTED UPTICK IN DEEP-LAYER NORTHERLY SHEAR WILL ERODE THE SYSTEM
FROM THE NORTH-NORTHWEST, AND COMBINED WITH MOVEMENT OVER STEADILY
COOLING WATERS, WILL KICK OFF A STEADY WEAKENING TREND WHICH IS
EXPECTED TO CONTINUE THROUGH THE REMAINDER OF THE FORECAST PERIOD.
AS THE SYSTEM CROSSES THE 26C ISOTHERM NEAR TAU 60, IT WILL BEGIN
TO FEEL THE EFFECTS OF STRONG WESTERLY FLOW ALOFT, AND BEGIN
SUBTROPICAL TRANSITION, WHICH IS EXPECTED TO BE COMPLETE NO LATER
THAN TAU 72, AS THE SYSTEM CROSSES THE 30N LATITUDE. RAPID
TRANSITION TO A WARM CORE EXTRATROPICAL LOW IS ANTICIPATED AS THE
SYSTEM CROSSES 35N AS IT BEGINS TO INTERACT WITH A STRONG POLAR
FRONT JET OVER NORTHERN JAPAN AND DEVELOPS STRONG THERMAL ADVECTION
AND FRONTAL CHARACTERISTICS. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
VERY TIGHT AGREEMENT, BOTH IN ALONG AND CROSS-TRACK SPREAD THROUGH
THE ENTIRETY OF THE FORECAST PERIOD. CROSS-TRACK SPREAD AT TAU 48
IS JUST 90NM, INCREASING 175NM BY TAU 96, WITH MINIMAL ALONG-TRACK
SPREAD. THE JTWC FORECAST LIES JUST EAST OF THE CONSENSUS MEAN
THROUGH THE FORECAST PERIOD WITH HIGH CONFIDENCE. INTENSITY GUIDANCE
IS IN GENERALLY GOOD AGREEMENT, WITH ALL BUT THE COAMPS-TC (GFS
VERSION), WHICH SHOWS NEAR-TERM INTENSIFICATION THROUGH TAU 12,
SUPPORTING A SLOW BUT STEADY WEAKENING TREND THROUGH THE FORECAST
PERIOD. THE JTWC FORECAST LIES CLOSE TO THE CONSENSUS MEAN THOUGH
THE MAJORITY OF THE FORECAST, EXCEPT FOR A SHORT DEVIATION HIGHER
DURING THE FIRST 12 HOURS, WITH MEDIUM CONFIDENCE. OF NOTE THE DCAP 
(DECAPITATION) MODEL INDICATES STRONG POTENTIAL OF A DECAPTITATION 
SCEAERNIO, PARTICULARLY AFTER TAU 24, LEADING A 30 KNOT WEAKENING 
THROUGH TAU 36. 

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