WDPN31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.9N 132.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 327 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS AN EXPOSED,
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) POSITIONED ALONG
THE WESTERN EDGE OF A SYMMETRIC AREA OF DEEP CONVECTION. AN 180651Z
SSMI 85GHZ COMPOSITE MICROWAVE IMAGE ALSO REVEALS SHALLOW BANDING
WRAPPING INTO A DEFINED LLCC WITH CURVED DEEP CONVECTIVE BANDING
OVER THE EASTERN QUADRANT, WHICH SUPPORTS THE INITIAL POSITION WITH
HIGH CONFIDENCE. THE INITIAL INTENSITY OF 35 KTS IS HEDGED SLIGHTLY
ABOVE THE PGTW, RJTD DVORAK ESTIMATES BASED ON ASCAT DATA SHOWING A
SWATH OF 30-40 KNOT SOUTHERLY WINDS OVER THE EASTERN PERIPHERY.
ENVIRONMENTAL ANALYSIS INDICATES MARGINALLY FAVORABLE CONDITIONS 
WITH GRADUALLY IMPROVING POLEWARD OUTFLOW OVER THE WESTERN 
SEMICIRCLE AS THE UPPER LOW TO THE NORTH-NORTHWEST WEAKENS AND 
SHIFTS POLEWARD INTO THE WEST SEA. ALTHOUGH MID-LEVEL DRY AIR 
ENTRAINMENT AND MODERATE VERTICAL WIND SHEAR (VWS) CONTINUE TO 
HINDER CONVECTIVE DEVELOPMENT OVER THE LLCC, EQUATORWARD OUTFLOW 
REMAINS ROBUST WITH WARM SST VALUES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED OVER
HONSHU EXTENDING SOUTHWARD OVER THE NORTHEASTERN AND EASTERN
PERIPHERY OF THE SYSTEM.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 32 KTS AT 180540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 09W IS TRACKING NORTH-NORTHWESTWARD ALONG
THE PERIPHERY OF THE STR BUT IS EXPECTED TO GRADUALLY TURN WESTWARD
AS THE DEEP UPPER LOW IN THE WEST SEA FILLS AND SHIFTS WEST
ALLOWING THE STR TO BUILD OVER THE EAST CHINA SEA BY TAU 24. DESPITE 
A SLIGHT IMPROVEMENT IN ORGANIZATION, TS 09W CONTINUES STRUGGLING TO 
CONSOLIDATE DUE PRIMARILY TO THE MODERATE VWS AND DRY AIR 
ENTRAINMENT, THEREFORE, TS 09W SHOULD SLOWLY INTENSIFY THROUGH TAU 
24. AFTER TAU 24, ENVIRONMENTAL CONDITIONS SHOULD GRADUALLY IMPROVE 
ALLOWING THE SYSTEM TO VENT AND SUSTAIN MORE CENTRALIZED DEEP 
CONVECTION, WHICH WILL MOISTEN THE MID-LEVELS. THIS SHOULD LEAD TO A 
FASTER RATE OF INTENSIFICATION WITH A PEAK OF 85 KNOTS ANTICIPATED 
BY TAU 96. AFTER TAU 96, INTERACTION WITH TAIWAN WILL WEAKEN THE 
SYSTEM.   

MODEL DISCUSSION: DUE TO THIS EVOLVING SYNOPTIC PATTERN, THERE IS
INCREASING UNCERTAINTY IN THE TRACK FORECAST AFTER TAU 24. NUMERICAL 
MODEL GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 72 WITH A 115NM 
SPREAD IN SOLUTIONS AT TAU 72. AFTER TAU 72, MODEL GUIDANCE
DIVERGES WITH A LARGE SPREAD AND LOW CONFIDENCE DUE TO POTENTIAL
DIRECT CYCLONE INTERACTION WITH INVEST 99W, WHICH IS EXPECTED TO
GRADUALLY STRENGTHEN OVER THE NEXT FEW DAYS. THERE IS LOW
CONFIDENCE IN THE JTWC INTENSITY FORECAST IN THE EXTENDED PERIOD
WITH A LARGE SPREAD IN INTENSITY GUIDANCE ASSOCIATED WITH THE
COMPLEX, EVOLVING ENVIRONMENT.   

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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