WDPN31 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (NAKRI) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.2N 131.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 208 NM EAST-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT
AND WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC), WHICH HAS
BECOME INCREASINGLY OBSCURED OVER THE LAST COUPLE OF HOURS DUE TO
CONVECTION DEVELOPING NEAR THE LLCC. A LARGER REGION OF DEEP
CONVECTION, WITH AN UPPER-LEVEL MESOCYCLONE, HAS PERSISTED
APPROXIMATELY 120NM TO THE SOUTH OF THE LLCC, IN THE VICINITY OF
MINAMIDAITOJIMA. THE HAFS-A MODEL FIELDS PICKED UP ON THIS
ORIENTATION AND SUGGEST THAT THE LLCC ASSOCIATED WITH TS 29W WILL
INTERACT WITH THIS MESOCYCLONE OVER THE NEXT FEW HOURS, WHICH WILL
BE DISCUSSED IN MORE DETAIL BELOW. ANIMATED WATER VAPOR IMAGERY AND
200MB DERIVED MOTION WIND VECTORS FROM CIRA SHOW THE SYSTEM IS
SITUATED UNDER A 200MB RIDGE, WITH DUAL POLEWARD AND EQUATORWARD
OUTFLOW BEGINNING TO DEVELOP AS THE SYSTEM APPROACHES THE RIDGE
AXIS. A 100453Z AMSR2 COLOR ENHANCED 89GHZ IMAGE REVEALED
WELL-DEFINED BUT SHALLOW CONVECTIVE BANDS SPIRALING INTO THE LLCC
AS WELL AS WEAKER MID-LEVEL BANDING FEATURES WRAPPING INTO THE
MESOVORTEX TO THE SOUTH. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN THE MSI. THE
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON
PERSISTENCE AND AN AVERAGE OF THE OBJECTIVE AND SUBJECTIVE
INTENSITY ESTIMATES NOTED BELOW. THE ENVIRONMENT HAS IMPROVED
CONSIDERABLY OVER THE PAST 24 HOURS, WITH A MUCH MORE MOIST
ATMOSPHERE, MINIMAL SHEAR AND IMPROVING DUAL-CHANNEL OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN EDGE OF A COL REGION CENTERED
TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS SATCON: 39 KTS AT 100406Z
   CIMSS ADT: 28 KTS AT 100540Z
   CIMSS AIDT: 34 KTS AT 100540Z
   CIMSS D-MINT: 29 KTS AT 100406Z
   CIMSS D-PRINT: 25 KTS AT 100540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: SINCE 100000Z, TS 29W HAS PROGRESSIVELY TURNED
ONTO A MORE NORTHWESTWARD TRACK, AND IS NOW TRACKING WEST-NORTHWEST
OR EVEN CLOSE TO DUE WEST. THIS IS LIKELY IN RESPONSE TO THE
DEVELOPMENT OF THE MESOCYCLONE TO THE SOUTH, WHICH IS DRAWING THE
LLCC ASSOCIATED WITH TS 29W TOWARDS IT. THE HAFS-A MODEL DEPICTS
THIS SCENARIO WELL, SHOWING THE LLCC BEING PULLED SOUTHWARD,
MERGING WITH THE MESOCYCLONE WITHIN THE NEXT 12-18 HOURS AND THEN
TRACKING NORTHWARD AFTER TAU 18. WHILE THESE MESOSCALE INTERACTIONS
AND POTENTIALLY ERRATIC NEAR-TERM MOTION ARE NOT CAPTURED IN THE
12HR TIMESTAMPS OF THE FORECAST DIRECTLY, THE OVERALL TRACK IS
CAPTURED FAIRLY WELL. THE SYSTEM IS CURRENTLY MOVING INTO A COL
REGION BETWEEN SUBTROPICAL RIDGE (STR) CENTERS OVER COASTAL CHINA
AND SOUTH OF TOKYO, GENERATING A VERY WEAK STEERING PATTERN, THUS
ALLOWING FOR THE ERRATIC MOTION EXPECTED IN THE NEAR-TERM. OVER THE
NEXT 24 HOURS, THE RIDGE TO THE EAST BUILDS AND MOVES FURTHER WEST
WHILE THE RIDGE TO THE WEST WEAKENS AND REMAINS STATIONARY. THIS
WILL STRENGTHEN THE STEERING GRADIENT ON THE EAST SIDE OF TS 29W
AND PUSH IT NORTHWARD AFTER TAU 18. BY TAU 24, THE SYSTEM WILL HAVE
ROUNDED THE RIDGE AXIS AND BEGIN ACCELERATING TOWARDS THE NORTHEAST
ALONG THE NORTHERN SIDE OF THE LARGE RIDGE TO THE SOUTH OF TOKYO.
BY TAU 72, THE RIDGE WILL FLATTEN OUT TO AN EAST-WEST ORIENTATION
AND TS 29W WILL SHIFT TO AN EASTWARD TRACK THROUGH THE REMAINDER OF
THE FORECAST. IN TERMS OF INTENSITY, THE SYSTEM HAS CONTINUED TO
STRUGGLE OVER THE LAST DAY, BUT CONDITIONS ARE BECOMING MORE
CONDUCIVE FOR INTENSIFICATION. HOWEVER, IF THE LLCC DOES EVENTUALLY
MERGE WITH THE MESOCYCLONE TO THE SOUTH, THE CIRCULATION WILL
LIKELY EXPERIENCE SOME DISRUPTION, AT LEAST FOR A SHORT TIME,
BEFORE REORGANIZING AROUND TAU 24. SLIGHT INTENSIFICATION IS
EXPECTED THROUGH TAU 24, PICKING UP THE PACE AFTER TAU 24 AS THE
SYSTEM STARTS TO TAP INTO A MORE ROBUST POLEWARD OUTFLOW CHANNEL.
PEAK INTENSITY OF 75-80 KNOTS IS EXPECTED TO OCCUR BETWEEN TAU 48
AND TAU 72, ROUGHLY AS THE SYSTEM PASSES HACHIJO-JIMA. THE SYSTEM
WILL BEGIN EXTRATROPICAL TRANSITION BY TAU 72, WITH ETT COMPLETION
EXPECTED BY TAU 96. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GENERAL
AGREEMENT ON THE OVERALL TRACK SCENARIO, BUT UNCERTAINTY HAS
INCREASED OVER THE LAST COUPLE OF MODEL RUNS. THE ONLY MODELS
DEPICTING A MORE WESTWARD TRACK THROUGH TAU 12 ARE THE HAFS-A AND
THE GOOGLE DEEP MIND MODEL, NEITHER OF WHICH ARE MEMBERS OF THE
TRACK CONSENSUS. THE JTWC FORECAST IS POSITIONED CLOSE TO THESE
MODEL TRACKERS THROUGH TAU 24. CROSS-TRACK SPREAD INCREASES AFTER
TAU 24 TO 100NM BY TAU 72 AND 150NM BY TAU 96. BUT ALONG-TRACK
SPREAD IS THE BIGGER CONCERN, INCREASING SHARPLY TO 200NM BY TAU
48, 320NM BY TAU 72 AND 725NM BY TAU 96. THE JTWC FORECAST IS
POSITIONED RELATIVELY CLOSE TO THE EMCWF AND EC-AIFS, SIGNIFICANTLY
SLOWER THAN THE CONSENSUS MEAN, FROM TAU 24 THROUGH TAU 96.
CONFIDENCE IS LOW THROUGHOUT THE FORECAST, DUE TO THE POTENTIAL FOR
ERRATIC MOTION IN THE SHORT-TERM AND THE EXTREMELY HIGH UNCERTAINTY
IN TRACK SPEEDS IN THE LONG-TERM. INTENSITY GUIDANCE CONTINUES TO
BE MIXED, WITH THE SHIPS GUIDANCE SHOWING LIMITED INTENSIFICATION
TO A PEAK OF 45-50 KNOTS AT TAU 36, WHILE THE MESOSCALE MODELS
DEPICT A PEAK INTENSITY BETWEEN 70-90 KNOTS BETWEEN TAU 60 AND TAU
72. THE COAMPS-TC ENSEMBLE SHOWS A 40 PERCENT PROBABILITY OF RAPID
INTENSIFICATION (RI) BETWEEN TAU 36 AND TAU 60, WHILE THE CTR1 RI
AID IS TRIPPED, REACHING A PEAK OF 95 KNOTS AT TAU 60. THE JTWC
FORECAST IS PLACED NEAR THE HAFS-A MODEL OUTPUT FOR THE ENTIRE
FORECAST PERIOD WITH MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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