WDPN31 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE) WARNING 
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.3N 133.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 423 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED,
BROAD LOW-LEVEL CIRCULATION CENTER (LLCC) POSITIONED ALONG THE
WESTERN EDGE OF A SWATH OF DEEP CONVECTION ASSOCIATED WITH AN
EXTENSIVE SWATH OF CONVERGENT SOUTHERLY LOW-LEVEL FLOW. A 170415Z
AMSR2 89GHZ COMPOSITE MICROWAVE IMAGE REVEALS WEAKLY-DEFINED
SHALLOW BANDING WRAPPING AROUND AN ELONGATED, DEFINED LLCC. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON MSI AND
THE AFOREMENTIONED AMSR2 IMAGE. THE INITIAL INTENSITY OF 30 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE DVORAK ESTIMATE FROM
KNES AND A 162335Z ASCAT-A PARTIAL IMAGE SHOWING A SWATH OF 25-30
KNOT SOUTHERLY WINDS OVER THE EASTERN PERIPHERY. ENVIRONMENTAL
ANALYSIS INDICATES MARGINALLY FAVORABLE CONDITIONS WITH CONVERGENT
UPPER-LEVEL WESTERLIES AND MID-LEVEL DRY AIR ENTRAINMENT OVER THE
WESTERN SEMICIRCLE OFFSET BY ROBUST POLEWARD AND EQUATORWARD
OUTFLOW AND WARM SST VALUES.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED EAST
OF HONSHU (36N 143E) EXTENDING SOUTHWARD OVER THE NORTHEASTERN AND
EASTERN PERIPHERY OF THE SYSTEM.  

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 45 KTS AT 170540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 09W IS TRACKING NORTHWESTWARD ALONG THE
PERIPHERY OF THE STR BUT IS EXPECTED TO GRADUALLY TURN
WEST-NORTHWESTWARD AS A DEEP UPPER LOW CURRENTLY LOCATED WEST OF
KYUSHU FILLS AND SHIFTS WEST ALLOWING THE STR TO BUILD OVER THE
EAST CHINA SEA BY TAU 48. TD 09W IS CURRENTLY STRUGGLING TO
CONSOLIDATE DUE PRIMARILY TO THE CONVERGENCE ALOFT AND DRY AIR
ENTRAINMENT, THEREFORE, TD 09W SHOULD SLOWLY INTENSIFY THROUGH TAU
24. AFTER TAU 24, ENVIRONMENTAL CONDITIONS SHOULD GRADUALLY IMPROVE
AS THE UPPER LOW AND CONVERGENCE ALOFT WEAKEN 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 120.    
   

MODEL DISCUSSION: DUE TO THIS EVOLVING SYNOPTIC PATTERN, THERE IS
INCREASING UNCERTAINTY IN THE TRACK FORECAST AFTER TAU 48.
NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 48 WITH A
90NM SPREAD IN SOLUTIONS AT TAU 48. AFTER TAU 48, MODEL GUIDANCE
DIVERGES WITH JGSM INDICATING A FASTER NORTHWESTWARD TRACK OVER
SHANGHAI, CHINA, AND GFS AND UKMET INDICATING A SHARPER WESTWARD
TURN TOWARD NORTHERN TAIWAN. THE BULK OF THE GUIDANCE SUPPORTS THE
JTWC TRACK FORECAST WITH LOW CONFIDENCE IN THE EXTENDED PERIOD.
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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