WDPN31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (TALAS) 
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.0N 135.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 212 NM SOUTHEAST OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A MORE
RAGGED AND SHEARED SYSTEM WITH A FULLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC). ALL OF THE CONVECTIVE STRUCTURE HAS
SHEARED OVER MAINLAND HONSHU LEAVING THE LLCC 100NM SOUTHEAST OF
SHIKOKU, JAPAN. A PARTIAL PASS FROM A 230637Z GMI 89GHZ MICROWAVE
IMAGE INDICATES THE CONVECTION OVER THE KYOTO REGION. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI IMAGERY AND
THE GMI MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 30 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON DOWNWARD TRENDING DVORAK
AGENCY INTENSITY FINAL ESTIMATES AT T1.5 BUT HELD HIGHER DUE TO
CONSTRAINTS LISTED BELOW. THE STRONG POLEWARD OUTFLOW REMAINS THE
ONLY ENVIRONMENTAL CONDITION FAVORABLE AS ALL OTHER CONDITIONS ARE
WANING ON THE SYSTEM TO INCLUDE VWS AND LOWERING SSTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA FROM AN OLDER 230128Z
METOP-B ASCAT IMAGE.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
EAST-SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 230550Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 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: TS 17W WILL MAINTAIN ITS INTENSITY BASED ON
THE OVERALL MARGINALLY UNFAVORABLE ENVIRONMENT, WHERE VERTICAL WIND
SHEAR (VWS) IS AN INHIBITING FACTOR ALONG WITH COOLING OCEAN SSTS.
THE SYSTEM IS FORECAST TO CONTINUE ON A NORTHEAST TRACK UNTIL
REACHING LANDFALL NEAR THE TOYOHASHI CITY, JAPAN, BETWEEN TAU 12
AND 24. THE SYSTEM WILL BEGIN DISSIPATING ONCE LANDFALL OCCURS DUE
TO THE LAND INTERACTION AND THE APPROACHING UPPER-LEVEL TROUGH
NORTHWEST OF THE SYSTEM. THIS INTERACTION BETWEEN THE SYSTEM AND
THE UPPER-LEVEL FEATURE WILL INDUCE INCREASED VERTICAL WIND SHEAR
(VWS), FURTHER DISRUPTING THE SYSTEMS TROPICAL CONVECTIVE
STRUCTURE. AFTER TAU 36, 17W WILL CONTINUE DISSIPATING AND FINALLY
COMPLETE DISSIPATION BY TAU 48 IF NOT SOONER.    

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT EXCLUDING NVGM AND JGSM, WITH ONLY A 40NM SPREAD UP TO
TAU 24. ONCE THE SYSTEM MAKES LANDFALL BOTH THE CROSS-TRACK AND
ALONG-TRACK VARIABILITY EXACERBATES THE SPREAD TO 140NM BY TAU 48.
DUE TO THE WEAK LLC, THE MODELS ARE STRUGGLING TO RESOLVE THE EXIT
OF THE WEAK CIRCULATION BACK OUT OVER WATER. THUS, THE JTWC
OFFICIAL TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE. THE JTWC
INITIAL INTENSITY IS CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM
CONFIDENCE THROUGHOUT THE FORECAST PERIOD.

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