****0000003714****
WDPN32 PGTW 291500

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//

SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (JEBI)

WARNING NR 013//

RMKS/

1. FOR METEOROLOGISTS.

2. 6 HOUR SUMMARY AND ANALYSIS.



SUMMARY:

   INITIAL POSITION: 24.7N 140.8E

   INITIAL INTENSITY: 35 KTS

   GEOGRAPHIC REFERENCE: 28 NM WEST-SOUTHWEST OF IWO TO

   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS

   SIGNIFICANT WAVE HEIGHT: 14 FEET



SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:

ANIMATED WATER VAPOR IMAGERY AND UW-CIMSS UPPER-LEVEL WINDS REVEAL

EXPANDING OUTFLOW OVER THE WESTERN SEMICIRCLE AND IMPROVING

POLEWARD VENTING, ENHANCED BY A DEEP UPPER-LEVEL TROUGH DIGGING INTO

WESTERN JAPAN. DUE TO THE IMPROVING UPPER-LEVEL ENVIRONMENT, ANIMATED

ENHANCED INFRARED SATELLITE IMAGERY SHOWS DEEP CONVECTION BUILDING

OVER THE LOW-LEVEL CIRCULATION. A 291150Z MHS 89GHZ MICROWAVE IMAGE

DEPICTS CURVED CONVECTIVE BANDING OVER THE EASTERN SEMICIRCLE

WRAPPING INTO THE NORTHEAST QUADRANT. A 291130Z PARTIAL ASCAT-B

IMAGE SHOWS A SWATH OF GALE-FORCE WINDS OVER THE EASTERN SEMICIRCLE

SUPPORTING THE INITIAL INTENSITY ASSSESSMENT OF 35 KNOTS. SURFACE

OBSERVATIONS FROM IWO-TO INDICATE SUSTAINED EAST-SOUTHEASTERLY SURFACE

WINDS OF 28 KNOTS (10-MINUTE AVERAGE) GUSTING TO 40 KNOTS, WHICH ALSO

SUPPORTS THE INITIAL INTENSITY ASSESSMENT. THE INITIAL POSITION IS

PLACED WITH MEDIUM CONFIDENCE BASED ON THE MHS MICROWAVE IMAGE.



INITIAL WIND RADII BASIS: PERSISTENCE



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

   KNES: T2.0 - 30 KTS

   CIMSS SATCON: 40 KTS AT 290920Z

   CIMSS ADT: 35 KTS AT 291200Z

   CIMSS AIDT: 37 KTS AT 291200Z



FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE

   VWS: 5-10 KTS

   SST: 28-29 CELSIUS

   OUTFLOW: MODERATE POLEWARD



ANALYSIS CONFIDENCE:

   INITIAL POSITION: MEDIUM

   INITIAL INTENSITY: MEDIUM

   INITIAL WIND RADII: LOW



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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