WDPN32 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (JEBI) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.9N 141.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 688 NM SOUTH OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED WATER VAPOR IMAGERY AND UW-CIMSS UPPER-LEVEL WINDS REVEAL A 
SLOWLY IMPROVING ENVIRONMENT, WITH THE BROAD UPPER-LEVEL LOW AND LARGE 
SUBSIDENT REGION SHIFTING TO A SLIGHTLY MORE FAVORABLE CONFIGURATION 
TO THE WEST, ALLOWING FOR IMPROVED POLEWARD VENTING. AS INDICATED IN 
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI), DEEP CONVECTION HAS 
BEGUN TO BUILD OVER THE BROAD CENTER. HOWEVER, DUE TO THE BROAD NATURE 
OF THE CENTER, THERE ARE MULTIPLE MESOVORTICIES ROTATING CYCLONICALLY 
AROUND A DEFINED CENTROID. THUS, THERE IS MEDIUM CONFIDENCE IN THE 
INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED 
ON RECENT SCATTEROMETRY DATA, WHICH IS ALSO SUPPORTED BY CIMSS 
OBJECTIVE INTENSITY ESTIMATES.  

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) ENTRENCHED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 290600Z
   CIMSS AIDT: 35 KTS AT 290600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TROPICAL STORM (TS) 19W IS FORECAST TO TRACK
NORTHWARD ALONG THE WESTERN PERIPHERY OF THE STR THROUGH TAU 36.
STEADY INTENSIFICATION IS ANTICIPATED AS THE UPPER-LOW TO THE WEST,
CURRENTLY INHIBITING SIGNIFICANT INTENSIFICATION, FILLS ALLOWING
FOR IMPROVED POLEWARD VENTING. AFTER TAU 36, THE SYSTEM WILL BEGIN
TO ROUND THE STR AND COMMENCE EXTRA-TROPICAL TRANSITION (ETT) AS IT
INTERACTS WITH A SHORTWAVE TROUGH SOUTH OF MAINLAND JAPAN. THE PEAK
INTENSITY OF 60 KNOTS WILL OCCUR NEAR TAU 48 DUE TO ROBUST POLEWARD
OUTFLOW INTO THE AFOREMENTIONED UPPER-LEVEL TROUGH. THE SYSTEM WILL
COMPLETE ETT BY TAU 72 AS IT ACCELERATES INTO THE MIDLATITUDE
WESTERLIES EAST OF HOKKAIDO AND RAPIDLY GAINS FRONTAL CHARACTERISTICS. 
AFTER TAU 60, THE SYSTEM WILL WEAKEN QUICKLY DUE TO INCREASING 
VERTICAL WIND SHEAR AND COOLER SST VALUES LESS THAN 25C.    

MODEL DISCUSSION: DETERMINISTIC AND PROBABILISTIC TRACK GUIDANCE
REMAINS IN FAIR AGREEMENT THROUGH THE FORECAST PERIOD, WITH
GUIDANCE INDICATING SOME POTENTIAL FOR THE SYSTEM TO TRACK CLOSER
TO THE KANTO PLAIN REGION. THE BULK OF THE SOLUTIONS, HOWEVER,
REMAIN WELL EAST OF HONSHU. NUMERICAL GUIDANCE CONTINUES TO
INDICATE A RELATIVELY SMALL GALE-FORCE WIND AREA ASSOCIATED WITH
THE SYSTEM, WHICH WILL LIMIT THE IMPACT ON CENTRAL HONSHU AS THE
SYSTEM PASSES.  

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