WDPN32 PGTW 060900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (LEEPI)        
WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 36.9N 149.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 446 NM EAST-SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SHALLOW
AND INCREASINGLY DISORGANIZED CONVECTION SHEARING AWAY FROM THE LOW
LEVEL CIRCULATION CENTER (LLCC). WEAK EQUATORWARD OUTFLOW CONTINUES
TO PERSIST BUT IS DOING LITTLE TO AID IN DEVELOPMENT AS THE SYSTEM
GRAPPLES WITH THE CHANGING ENVIRONMENTAL CONDITIONS OF HIGHER
LATITUDES. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON A 060013Z ASCAT IMAGE SHOWING A BROAD SWATH OF
25-30 KT WINDS ALONG THE ENTIRETY OF THE EAST-SOUTHEASTERN SEMI-CIRCLE 
WITH A PEAK OF 35 KTS RECORDED IN THE SOUTHEAST QUADRANT. THIS DATA 
JUSTIFIED AN UPGRADE DUE TO THE SYSTEM MAINTAINING A VERY BORDERLINE 
INTENSITY OVER THE PAST 24 HOURS AND IS SUPPORTED BY THE SUBJECTIVE 
AGENCY DVORAK ESTIMATES. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON A 060540Z VISIBLE SATELLITE IMAGERY SHOWING AN 
EXPOSED LLCC AND SHALLOW SPIRAL CONVECTIVE BANDING.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP LAYER STR TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 46 KTS AT 060258Z
   CIMSS ADT: 32 KTS AT 060600Z
   CIMSS AIDT: 41 KTS AT 060600Z
   CIMSS DPRINT: 31 KTS AT 060600Z
   CIMSS DMINT: 35 KTS AT 060501Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 30+ KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: INCREASING VWS VALUES (29-42 KTS) AND
PLUMMETING SSTS WILL CREATE AN INHOSPITABLE ENVIRONMENT THAT WILL
HAMPER ANY FURTHER DEVELOPMENT. INTERACTION WITH A THERMAL RIBBON
BEGINS AT TAU 24 AS THE SYSTEM HURRIES TOWARD THE POLAR FRONT,
WHICH WILL INITIATE EXTRATROPICAL TRANSITION. BY TAU 36, THE POLAR
FRONT WILL BOMBARD TS 13W FROM THE NORTHWEST, AT WHICH POINT IT
WILL BE CONSIDERED TO HAVE FULLY TRANSITIONED TO AN EXTRATROPICAL
CYCLONE. THE SYSTEM IS FORECAST TO MAINTAIN AN INTENSITY OF 35 KTS
DUE TO A COMBINATION OF FACTORS THAT INCLUDE ITS PROXIMITY TO
STRONG RIDGING TO THE EAST, LEADING TO A TIGHTENED PRESSURE
GRADIENT ALONG THE EAST SIDE, AND COMPOUNDED BY THE ACCELERATING
FORWARD SPEEDS (APPROXIMATELY 17-23 KTS).

MODEL DISCUSSION: THE RELIABLE MODEL CONSENSUS HAS MAINTAINED A
VERY SOLID HANDLE ON THE TRACK, DEPICTING A VERY NARROW GROUPING
ALONG THE FORECAST WITH A TAU 24 CROSS-TRACK SPREAD OF 26 NM AND A
TAU 36 CROSS-TRACK SPREAD OF 45 NM. THE INTENSITY GUIDANCE
CONSENSUS (ICNW) BUMPS THE INTENSITY UP SLIGHTLY AT TAU 24, BUT NOT
ENOUGH TO REFLECT ANY INTENSITY CHANGES IN THE FORECAST. OVERALL, A
GRADUAL DECLINE IN THE INTENSITY IS PREDICTED, BUT WITH THE
RESULTING INTENSITY STILL HOLDING CLOSE TO BETWEEN 25-35 KTS BY TAU
36. ACCOUNTING FOR A CONTINUED GRADIENT-INDUCED WIND FIELD
ACCELERATION ON THE EASTERN SIDE OF THE SYSTEM, THE JTWC INTENSITY
FORECAST HOLDS INTENSITY CONSTANT THROUGH THE END OF THE FORECAST
PERIOD, WHICH IS HEDGED SLIGHTLY ABOVE THE ICNW GUIDANCE.
CONFIDENCE REMAINS HIGH FOR BOTH THE JTWC TRACK AND INTENSITY
FORECASTS.

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