WDPN31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (DOKSURI) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.6N 130.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 812 NM SOUTHEAST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RELATIVELY
BROAD, STILL DISORGANIZED AND PARTIALLY EXPOSED LOW LEVEL
CIRCULATION (LLC), WITH SPOTTY FLARING CONVECTION ACROSS THE
SOUTHERN AND SOUTHEASTERN PERIPHERY. CLOUD TOP TEMPERATURES REMAIN
ANEMIC, WITH THE COLDEST TOPS OF ISOLATED CONVECTIVE BURSTS BARELY
REACHING -80C. VERY DRY, SUBSIDENT AIR ASSOCIATED WITH A STRONG,
DEEP SUBTROPICAL RIDGE (STR) REMAINS FIRMLY ENSCONCED ACROSS THE
NORTHERN AND NORTHWESTERN FLANK OF THE SYSTEM, PRECLUDING
SIGNIFICANT CONVECTIVE DEVELOPMENT OVER THAT HALF OF THE
CIRCULATION. WHILE THE LATEST CIMSS ANALYSIS SUGGESTS VERY WEAK
DEEP-LAYER SHEAR (APPROXIMATELY 4 KNOTS), THE VORTEX REMAINS TILTED
AND DISJOINTED ACCORDING TO HAFS-A CROSS-SECTION DATA. THE INITIAL
POSITION IS ASSESSED WITH MEDIUM CONFIDENCE USING THE ANIMATED
VISIBLE IMAGERY AS WELL AS A PARTIAL 220509Z AMSR2 36GHZ MICROWAVE
IMAGE. THE INITIAL INTENSITY REMAINS SET AT 35 KNOTS, ASSESSED WITH
HIGH CONFIDENCE BASED ON A CONVERGENCE OF AVAILABLE DVORAK CURRENT
INTENSITY ESTIMATES OF T2.5, SUPPORTED BY THE ADT, AIDT AND SATCON
ESTIMATES. OVERALL, THE ENVIRONMENT CONTINUES TO BE FAVORABLE, WITH
LOW (5-10 KNOTS) VWS, VERY WARM SSTS, HIGH OHC AND GOOD EQUATORWARD
OUTFLOW, ENHANCED BY STRONG EASTWARD OUTFLOW INTO A TUTT-CELL TO
THE NORTHEAST. OUTFLOW IS CONSTRAINED TO THE NORTH DUE TO PRESENCE
OF PERSISTENT, STRONG NORTHEASTERLY FLOW PUSHING SOUTH OF 20N. THIS
NORTHEASTERLY FLOW IS ALSO USHERING IN THE DRY AIR PREVIOUSLY
DISCUSSED, WHICH IS INHIBITING CONVECTIVE CONSOLIDATION,
CONTRIBUTING TO THE SLOW PACE OF DEVELOPMENT OF THE SYSTEM.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 37 KTS AT 220436Z
   CIMSS ADT: 33 KTS AT 220530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR TO THE NORTH AND EASTWARD OUTFLOW INTO
THE TUTT-CELL TO THE NORTHEAST. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: THROUGH THE NEXT 36 HOURS OR SO, TROPICAL
STORM (TS) DOKSURI IS EXPECTED TO SLOWLY MOVE WESTWARD, ALONG THE
SOUTHERN PERIPHERY OF THE STRONG STR ENTRENCHED TO THE NORTH. THE
CONTINUED PRESENCE OF THE DRY AIR TO THE NORTH, ALONG WITH THE
CONSTRAINED POLEWARD OUTFLOW, MEANS THAT THE SYSTEM WILL STRUGGLE
FOR THE NEXT DAY. AS TUTT-CELL MOVES FURTHER WEST AND MOVES INTO A
MORE FAVORABLE POSITION, UPPER-LEVEL OUTFLOW IS EXPECTED TO IMPROVE
AS THE NORTHEASTERLY FLOW ALOFT IS REPLACED BY A DIVERGENT FLOW
INTO THE TUTT. AS THIS PROCESS OCCURS, THE LOW-LEVEL VORTEX WILL
ALIGN, KICKING OFF MORE ROBUST AND ORGANIZED CONVECTION, WHICH WILL
SERVE TO DEVELOP A POINT SOURCE ALOFT AND ENHANCE OUTFLOW EVEN MORE
IN A POSITIVE FEEDBACK CYCLE. BY TAU 24, THE SYSTEM IS EXPECTED TO
HAVE BECOME WELL-ORGANIZED, VERTICALLY STACKED AND PRIMED FOR
FURTHER INTENSIFICATION. BY 48, THE STEERING PATTERN BEGINS TO
CHANGE, WITH THE STR CURRENTLY DUE NORTH OF THE SYSTEM, MOVING OFF
TO THE EAST TO BECOME CENTERED EAST OF TOKYO, WHILE THE WESTERN
SIDE OF THE RIDGE COMPLEX ERODES UNDER THE INFLUENCE OF A DEEP
TROUGH MOVING IN FROM THE WEST. THE WEAKENING AND REPOSITIONING OF
THE RIDGE WILL ALLOW TS 05W TO TURN POLEWARD AFTER TAU 48,
CONTINUING ON A NORTHWESTWARD TRACK THROUGH THE REMAINDER OF THE
FORECAST PERIOD. IMPROVED OUTFLOW INTO A TUTT-CELL SOUTH OF KYUSHU
ALONG WITH MOVEMENT OVER A REGION OF HIGH OHC (EXCEEDING 110 KJ PER
CM2) WILL SUPPORT A PERIOD OF RAPID INTENSIFICATION, WITH THE
SYSTEM FORECAST TO INTENSIFY FROM 65 KNOTS AT TAU 36 TO 105 KNOTS
BY TAU 72. ADDITIONAL INTENSIFICATION TO A PEAK OF 110 KNOTS IS
EXPECTED BY TAU 96 BUT THE RATE OF INTENSIFICATION WILL BE
SIGNIFICANTLY LOWER DUE REDUCTION IN THE AMOUNT OF OUTFLOW AND SOME
MODERATELY ENHANCED SHEAR. LANDFALL ALONG THE NORTHEAST COAST OF
TAIWAN IS EXPECTED BETWEEN TAU 96 AND TAU 120, AND THEREAFTER THE
SYSTEM IS FORECAST TO CONTINUE TRACKING INTO THE NORTHERN PORTION
OF THE TAIWAN STRAIGHT BY THE END OF THE FORECAST. 

MODEL DISCUSSION: DETERMINISTIC GUIDANCE IS IN GOOD AGREEMENT
THROUGH THE FIRST 48 HOURS OF THE FORECAST, WITH ALL MEMBERS OF THE
CONSENSUS IN CONCURRENCE ON A GENERAL WESTWARD TRACK, TURNING
NORTHWEST BY TAU 48. AFTER THIS POINT HOWEVER, MODELS DIVERGE
SIGNIFICANTLY, WITH SPREAD RAPIDLY INCREASING TO 275 NM BY TAU 72
BETWEEN THE NAVGEM ON THE LEFT AND GFS ON THE RIGHT. BY TAU 120,
CROSS-TRACK SPREAD INCREASES TO 540 NM BETWEEN THE EGRR AND GFS
OUTLIERS. THE ECMWF, ECMWF ENSEMBLE, UKMET ENSEMBLE AND COAMPS-TC
(GFS) TRACKERS HAVE SLOWLY CONGEALED INTO A TIGHT GROUPING CENTERED
ON TAIWAN, BUT THIS GROUPING AND THE CONSENSUS MEAN CONTINUE TO
DRIFT EAST AND WEST FOR THE PAST SEVERAL MODEL RUNS. THE GFS
ENSEMBLE MEAN CONTINUES TO BE THE EXTREME OUTLIER ON THE RIGHT,
WHILE THE ECMWF, UKMET AND THE SUPER-ENSEMBLE MEAN BRING THE SYSTEM
OVER TAIWAN. THUS, THE JTWC FORECAST SLIDES A BIT WEST FROM THE
PREVIOUS FORECAST, NOW BRINGING THE SYSTEM OVER TAIWAN, WITH HIGH
TRENDING TO MODERATE CONFIDENCE. INTENSITY GUIDANCE REMAINS TIGHTLY
GROUPED, THOUGH TOO AGGRESSIVE, WITH THE BULK OF THE RAPID
INTENSIFICATION AIDS TRIGGERING. HOWEVER, DUE TO THE SLOW PACE OF
INTENSIFICATION INDUCED BY THE DRY AIR, IT IS UNLIKELY THAT RI WILL
COMMENCE IN THE NEAR-TERM. THE JTWC FORECAST IS SLIGHTLY BELOW THE
CONSENSUS MEAN THOUGH TAU 36, THEN TRANSITIONS TO THE HIGHER END OF
THE GUIDANCE PACKAGE AFTER TAU 72. THE HAFS-A TRACKER CONTINUES TO
PEAK SIGNIFICANTLY HIGHER THAN ALL THE OTHER MODELS, NEAR 130 KNOTS,
BUT IS CONSIDERED AN OUTLIER AND DISCOUNTED FOR THIS FORECAST. 

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