WDPN32 PGTW 150900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (CHANTHU) WARNING 
NR 037//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.2N 126.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 249 NM SOUTHWEST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM HAS
FURTHER DEVELOPED ITS CENTRAL CONVECTION, WHICH IS PARTLY OBSCURING
THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON A NOTCH FEATURE IN THE
150545Z GMI 37GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE OVERALL ASSESSMENT OF
AGENCY AND AUTOMATED DVORAK ESTIMATES. ANALYSIS INDICATES A
MARGINALLY FAVORABLE ENVIRONMENT WITH MODERATE EQUATORWARD OUTFLOW
AND LOW VWS. THE SYSTEM CONTINUES TO DEVELOP IN A COL REGION.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COL BETWEEN SUBTROPICAL RIDGE TO THE
NORTHWEST AND STR TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 51 KTS AT 150445Z
   CIMSS ADT: 47 KTS AT 150540Z

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

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: TRACK SHIFTED TO THE SOUTH ACROSS THE
SPINE OF JAPAN.

FORECAST DISCUSSION: TS 19W IS EXPECTED TO FINALLY BEGIN ITS
RECURVE AROUND THE SUBTROPICAL RIDGE, LOCATED TO ITS SOUTHEAST, BY
TAU 12.  THE MARGINALLY FAVORABLE ENVIRONMENT OVER THE NEXT 24
HOURS WILL LIKELY ALLOW FOR SLIGHT INTENSIFICATION TO 50 KNOTS AS
IT APPROACHES THE TSUSHIMA STRAIT UNDER INCREASED UPPER LEVEL
OUTFLOW, LOW SHEAR AND WARM SEA SURFACE TEMPERATURES (28-29 DEGREES
CELSIUS). AS THE SYSTEM TRACKS MORE POLEWARD, INCREASING VWS AND
LAND INTERACTION WILL WEAKEN IT AS IT PASSES OVER JAPAN AND BEGINS
EXTRATROPICAL TRANSITION. EXTRATROPICAL TRANSITION IS EXPECTED TO
COMPLETE NO LATER THAN TAU 72.

MODEL DISCUSSION: NUMERICAL MODELS HAVE PULLED TO THE RIGHT OF THE
PREVIOUS FORECAST, WITH LANDFALL EXPECTED SHORTLY AFTER TAU 48.
GIVEN THE UNCERTAINTY IN THE STORM MOTION IN THE COL, THERE IS ONLY 
MEDIUM CONFIDENCE IN THE JTWC TRACK FORECAST DESPITE TIGHT MODEL 
GROUPING. INTENSITY FORECAST CONFIDENCE IS MEDIUM DUE TO SUSTAINED 
COMPETING ENVIRONMENTAL FACTORS AND RECURVE TIMING.

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