WDPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 03W (GUCHOL) 
WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.1N 136.7E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 458 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 20 KTS
   SIGNIFICANT WAVE HEIGHT: 37 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
DISINTEGRATING SYSTEM EXHIBITING SIGNS OF RAPID VORTEX DECOUPLING.
A SERIES OF MICROWAVE PASSES BETWEEN 18Z AND 21Z SHOWED THE
PROGRESSIVE DECOUPLING, WITH THE LAST PASS AT 112113Z SHOWED A
COMPLETELY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) DISPLACED TO
THE WEST OF THE WEAKENING CONVECTION. THE INITIAL POSITION WAS
ASSESSED WITH HIGH CONFIDENCE BASED ON AN EXTRAPOLATION OF THE
AFOREMENTIONED MICROWAVE IMAGE AND A TIGHT GROUPING OF THE AGENCY
FIX POSITIONS. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE ROUGH MIDPOINT OF THE T3.0-T3.5 DVORAK
CURRENT INTENSITY ESTIMATES AS WELL AS BETWEEN THE ADT OF 45 KNOTS
AND THE AIDT OF 57 KNOTS. ADDITIONALLY, A 112046Z RCM3 SAR PASS
REVEALED A 54 KNOT MAX WIND IN THE SOUTHEAST QUADRANT, WITH
SLIGHTLY LESSER WINDS IN THE OTHER QUADRANTS. THE SYSTEM CONTINUES
RACING NORTHEAST ALONG THE WESTERN FLANK OF A DEEP SUBTROPICAL
RIDGE (STR) TO THE EAST. THE ENVIRONMENT CONTINUES TO WORSEN, WITH
EVER INCREASING WESTERLY SHEAR, AND DECREASING SSTS BEING OFFSET BY
ROBUST POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER STR
TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 45 KTS AT 112340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: BASED ON AUTOMATED AND MANUAL PHASE WORKSHEETS
AND THE FSU PHASE SPACE DIAGRAM, TS 02W IS CURRENTLY IN THE THROES
OF SUBTROPICAL TRANSITION (STT), HAVING MOVED INTO SUB-26C WATERS
AND UNDERGOING RAPID VORTEX DECOUPLING, OR DECAPITATION. THE SYSTEM
WILL CONTINUE TO MOVE RAPIDLY TOWARDS THE NORTHEAST AND QUICKLY
COMPLETE STT WITHIN THE NEXT 12 HOURS. THE SUBTROPICAL PHASE WILL
BE SHORT-LIVED HOWEVER AND THE SYSTEM WILL IMMEDIATELY BEGIN
EXTRATROPICAL TRANSITION (ETT) BY TAU 24 AS IT CROSSES INTO SUB-23C
WATERS, MOVES INTO PHASE WITH A 500MB SHORTWAVE TROUGH AND BEGINS
TO PULL COOL, DRY AIR INTO THE WESTERN FLANK OF THE CIRCULATION. AS
THE SYSTEM PASSES NORTH OF TOKYO AROUND TAU 36, IT IS EXPECTED TO
COMPLETE ETT, NO LATER THAN TAU 48 AS IT BECOMES EMBEDDED UNDER A
200MB JET MAX AND DEVELOPS FRONTAL CHARACTERISTICS. 

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN VERY GOOD AGREEMENT,
WITH MINIMAL CROSS- OR ALONG-TRACK SPREAD THROUGH THE SHORT
DURATION OF THE FORECAST. SIMILARLY, THE INTENSITY GUIDANCE IS ALSO
IN GOOD AGREEMENT THROUGH THE ETT PHASE, WITH ALL MODELS SUPPORTING
STEADY WEAKENING THROUGH TAU 48. WHILE AFTER THE FORECAST PERIOD,
THE BULK OF THE GUIDANCE SUGGESTS THAT THE SYSTEM COULD REINTENSIFY
BEYOND TAU 72 AS IT MOVES INTO THE NORTH PACIFIC AS AN
EXTRATROPICAL LOW PRESSURE SYSTEM. WITH THE TIGHT GROUPING OF BOTH
THE TRACK AND INTENSITY GUIDANCE, THERE IS HIGH CONFIDENCE IN THE
OVERALL JTWC FORECAST. 

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