WDPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (MEARI) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.4N 136.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 343 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS THE LOW
LEVEL CIRCULATION CENTER (LLCC) HAS BECOME FULLY EXPOSED OVER THE
LAST 6 HRS AS THE MAIN CONVECTION HAS BECOME FULLY DECOUPLED FROM
THE LLCC. THEREFORE, THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE ANIMATED MULTISPECTRAL IMAGERY WHICH SHOWS
A WELL DEFINED LOW LEVEL CIRCULATION ALONG WITH AGENCY DVORAK
POSITION FIXES. THE INITIAL INTENSITY IS CURRENTLY SET AT 35 KNOTS
WITH MEDIUM CONFIDENCE BASED ON A BLEND OF AGENCY DVORAK FIXES AND
THE FACT THAT THE SYSTEM IS STILL BEING HEAVILY IMPACTED BY HIGH
VERTICAL WIND SHEAR AND STILL STRUGGLING TO INTENSIFY.
ENVIRONMENTAL CONDITIONS ARE CURRENTLY MODERATELY CONDUCIVE FOR
DEVELOPMENT BASED ON COMPETING FACTORS OF WARM SURFACE TEMPERATURES
(29-30C), MODERATE EQUATORWARD OUTFLOW, SOMEWHAT OFFSET BY 25-30
KTS OF VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 112340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE 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: TS 09W IS FORECAST TO TRACK TO THE NORTH THEN
NORTH-NORTHEAST ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE AXIS. THE SYSTEM IS FORECAST TO CONTINUE TRACKING TO THE
NORTHEAST BEFORE MAKING LANDFALL ALONG THE IZU PENINSULA BETWEEN
TAU 24 AND TAU 36. MODELS DO SUGGEST THE WIND SHEAR WILL START TO
DECREASE WITHIN THE NEXT 24 HRS WHICH SHOULD ALLOW FOR MORE
CONSOLIDATION AS WELL AS AN INCREASE IN INTENSITY, DUE TO THE FACT
THAT THE SHEAR IS CURRENTLY THE MAIN INHIBITING FACTOR. THE
COMBINED EFFECT OF A DECREASE IN VERTICAL WIND SHEAR, INCREASE IN
POLEWARD UPPER LEVEL OUTFLOW ALOFT, ALONG WITH HIGH SEA SURFACE
TEMPERATURES (29-30C) WILL ALLOW FOR A BRIEF WINDOW OF
INTENSIFICATION UP TO 50 KTS JUST PRIOR TO LANDFALL. BY TAU 48 THE
SYSTEM WILL EMERGE BACK OVER WATER AND BEGIN TO QUICKLY ACCELERATE
TO THE NORTHEAST AS IT BEGINS TO INTERACT WITH AN APPROACHING UPPER
LEVEL TROUGH UPSTREAM. BY TAU 72 AND TAU 96 THE UPPER LEVEL TROUGH
WILL INDUCE EXTRATROPICAL TRANSITION AND THE SYSTEM IS FORECAST TO
COMPLETE EXTRATROPICAL TRANSITION AS IT APPROACHES THE KAMCHATKE
PENINSULA.

MODEL DISCUSSION: MODEL GUIDANCE REMAINS IN OVERALL GOOD AGREEMENT
ON THE TRACK FORECAST THROUGH TAU 48 WITH THE JTWC OFFICIAL
FORECAST REMAINING CLOSE TO CONSENSUS MODEL TRACK GUIDANCE. AFTER
TAU 72 AS THE SYSTEM BEGINS TO UNDERGO EXTRATROPICAL TRANSITION THE
CROSS TRACK AND ALONG TRACK VARIABILITY INCREASE IN THE CONSENSUS
MODELS WITH THE JTWC OFFICIAL FORECAST REMAINING CLOSE TO
CONSENSUS. INTENSITY GUIDANCE INDICATES A GRADUAL INCREASE IN
INTENSITY THROUGH TAU 24 BEFORE MAKING LANDFALL. BY TAU 48 AS THE
SYSTEM EMERGES BACK OVER COOLER WATERS THE MODEL GUIDANCE FORECAST
CALLS FOR A WEAKENING TREND THROUGH TAU 96 AND IS IN LINE WITH THE
JTWC INTENSITY FORECAST. FOR THESE REASONS THE JTWC TRACK AND
INTENSITY FORECASTS ARE PLACED WITH MEDIUM CONFIDENCE.   

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