WDPN31 PGTW 100300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (BARIJAT) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.6N 150.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 547 NM EAST-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 21W (BARIJAT) WITH A CONTINUED PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) TRACKING TO THE NORTHEAST. THE SYSTEM
REMAINS FLANKED BY SUSTAINED FLARING CONVECTION WITHIN THE NORTHERN
QUADRANT, WHILE STRONG UPPER-LEVEL SOUTHWESTERLIES ASSOCIATED WITH
A DEEP LONGWAVE TROUGH HAS CONTINUED TO DISLOCATE THE CIRRUS SHIELD
ALOFT TO THE NORTH AND EAST OF THE LLC. AS THE AFOREMENTIONED
LONGWAVE TROUGH REMAINS JUST POLEWARD OF TS 21W, THIS HAS ALLOWED
FOR A SUSTAINED AND SUPPORTIVE POLEWARD OUTFLOW CHANNEL, KEEPING
THE SYSTEMS INTENSITY ABOVE 30 KTS IN A RELATIVELY NON-CONDUCIVE
ENVIRONMENT AS SEA SURFACE TEMPERATURES SLOWLY DECREASE TO 26 C. AS
21W CONTINUES ITS NORTHWARD TRACK, DRY AIR CONTINUES TO WRAP
CYCLONICALLY ALONG THE WESTERN AND SOUTHERN QUADRANTS, KEEPING THE
ENTIRE WESTERN HALF OF THE LOW-LEVEL CIRCULATION CLEAR OF ANY
CONVECTIVE STRUCTURES. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON A 100010Z ASCAT-B IMAGE. THE INITIAL INTENSITY
IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED
ASCAT-B IMAGE SHOWING ISOLATED AREAS OF 35 KTS THROUGHOUT THE
EASTERN SEMICIRCLE.

INITIAL WIND RADII BASIS: SMOS DATA.

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 45 KTS AT 100030Z
   CIMSS ADT: 32 KTS AT 100030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TS 21W IS FORECASTED TO TRACK
NORTH-NORTHEASTWARD ALONG THE WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE TO THE EAST THROUGHOUT THE ENTIRETY OF THE
FORECAST PERIOD. DURING THE NEXT 12 HOURS, THE MARGINAL ENVIRONMENT
WILL BECOME LESS-CONDUCIVE FOR FURTHER TROPICAL INTENSIFICATION AS
THE SYSTEM IS EXPECTED TO BECOME FULLY EMBEDDED WITHIN THE
MID-LATITUDE UPPER-LEVEL WESTERLY FLOW. WHILE TS 21W TRACKS
NORTH-NORTHEASTWARD AFTER TAU 12, VERTICAL WIND SHEAR (VWS) IS
FORECASTED TO INCREASE ABOVE 25 KTS, SEA SURFACE TEMPERATURES (SST)
ARE EXPECTED TO DECREASE TO BELOW 26 C, AND DRY AIR WILL RE-ENTER
THE CORE CIRCULATION BETWEEN TAU 12 AND TAU 24, ALLOWING FOR THE
SYSTEM TO FULLY TRANSITION INTO A COLD-CORE EXTRATROPICAL LOW BY
TAU 36. ALTHOUGH 21W WILL BEGIN THE EXTRATROPICAL TRANSITION AWAY
FROM ITS ORIGINAL TROPICAL CHARACTERISTICS, THE SYSTEMS SURFACE
INTENSITY WILL INCREASE DUE TO UPPER-LEVEL SUPPORT THROUGH THE
DIFFLUENT FLOW ALOFT JUST DOWNSTREAM OF THE LONGWAVE TROUGH AXIS TO
THE NORTHWEST, REACHING A FORECASTED INTENSITY OF 50 KTS BY TAU 36.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THAT THE TRACK OF TS 21W WILL CONTINUE NORTH-NORTHEASTWARD
THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD, WITH A CROSS-TRACK 
SPREAD OF 138 NM BY TAU 24. FOLLOWING TAU 24, MODEL GUIDANCE BEGINS 
TO DIVERGE SLIGHTLY TO A CROSS-TRACK OF 187 NM BY TAU 36 AS
INTERACTION WITH THE MID-LATITUDE WESTERLIES DIFFER BETWEEN
DETERMINISTIC NUMERICAL MODEL GUIDANCE. THE JTWC TRACK FORECAST IS
ALIGNED CLOSELY WITH THE JTWC CONSENSUS MEMBERS WITH MEDIUM
CONFIDENCE. THE JTWC INTENSITY GUIDANCE IS IN FAIR AGREEMENT,
CHARACTERIZING AN INITIAL INTENSITY INCREASE THROUGH EXTRATROPICAL
TRANSITION WITH SUPPORT FROM THE UPPER-LEVEL LONGWAVE PATTERN UNTIL
TAU 36. THE JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE INTENSITY CONSENSUS, WITH THE EXCEPTION OF
COAMPS-TC, WHICH ILLUSTRATES AN INITIAL WEAKENING PHASE PRIOR TO TAU 
24 DUE TO THE EXTRATROPICAL TRANSITION JUST BEFORE THE END OF THE 
FORECAST PERIOD.

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