WDPN31 PGTW 312100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
033//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.6N 142.0E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 250 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TS 12W HAS MAINTAINED INTENSITY WHILE TRACKING STEADILY
NORTH-NORTHWESTWARD OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY DEPICTS A NEW BAND OF CONVECTION
BEGINNING TO DEVELOP ALONG THE EASTERN AND NORTHERN PERIPHERY OF
THE CIRCULATION, WITH SHALLOW BANDING ELSEWHERE AND A CLEAR CENTER. 
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE 
311730Z PGTW SATELLITE FIX AND 311453Z GMI 37 GHZ IMAGERY DEPICTING A 
MICROWAVE EYE FEATURE. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED 
WITH MEDIUM CONFIDENCE BASED ON 311412Z OCEANSAT-3 WIND SPEED DATA 
AND A CONSENSUS OF RECENT MULTI-AGENCY SUBJECTIVE DVORAK AND 
AUTOMATED INTENSITY ESTIMATES LISTED BELOW. RECENT MICROWAVE 
SATELLITE IMAGERY, INCLUDING A 311652Z AMSR2 PASS, SUGGESTS THAT THE 
CIRCULATION IS BEGINNING TO TILT WITH HEIGHT AS IT RESPONDS TO 
SOUTHWESTERLY FLOW ASSOCIATED WITH AN UPPER-LEVEL TROUGH TO THE WEST.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK AND SCATTEROMETER
DATA (311412Z OCEANSAT-3) 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGING TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 35 KTS AT 311730Z
   CIMSS AIDT: 42 KTS AT 311730Z
   CIMSS D-MINT: 47 KTS AT 311654Z
   CIMSS D-PRINT: 44 KTS AT 311900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 12W WILL CONTINUE TO TRACK
NORTH-NORTHWESTWARD FOR THE NEXT 12 HOURS UNDER THE STEERING
INFLUENCE OF SUBTROPICAL RIDGING TO THE EAST. THEREAFTER, TS 12W IS
EXPECTED TO CREST THE RIDGE AXIS AND TURN EAST-NORTHEASTWARD TO THE
EAST OF HONSHU AS A DEVELOPING SHORTWAVE TROUGH OVERTAKES THE
SYSTEM. FOLLOWING THE TURN, THE SYSTEM WILL ACCELERATE AND UNDERGO
EXTRATROPICAL TRANSITION AS IT MERGES WITH THE MID-LATITUDE
WESTERLY FLOW PATTERN. NEAR-TERM INTENSIFICATION IS EXPECTED AS THE
SYSTEM MOVES OVER WARMER WATER ASSOCIATED WITH THE KUROSHIO CURRENT
AND POLEWARD OUTFLOW IMPROVES. BY TAU 36, POST TURN, THE SYSTEM WILL 
PASS OVER COOLER WATER AND VERTICAL WIND SHEAR WILL BE TO INCREASE, 
LEADING TO STEADY WEAKENING OFFSET BY INITIALLY FAVORABLE BAROCLINIC
INFLUENCES DURING EXTRATROPICAL TRANSITION.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE MODEL TRACK FORECAST
GUIDANCE IS IN GOOD AGREEMENT REGARDING THE OVERALL SCENARIO AND
ORIENTATION OVER THE NEXT 72 HOURS. ALL CONSENSUS MEMBERS AND NEARLY 
EVERY ENSEMBLE MEMBER SOLUTION INDICATE A POLEWARD TRACK FOLLOWED BY A 
STEADY EASTWARD TURN TO THE EAST OF HONSHU OVER THE NEXT 36 HOURS. THE 
CURRENT FORECAST LIES IN THE MIDDLE OF THE WELL-PACKED CONSENSUS 
GROUPING AND IS CONSISTENT WITH THE PREVIOUS JTWC TRACK FORECAST. THE 
POSSIBILITY OF THE CENTER MAKING LANDFALL IS ALL BUT RULED OUT AT THIS 
POINT. HOWEVER, SMALL DEVIATIONS TO THE TRACK, EVEN A CLOSER PASSAGE 
TO HONSHU, ARE STILL POSSIBLE. IN THE EXTENDED PERIOD, TRACK FORECASTS 
DIVERGE A BIT IN THE CROSS-TRACK DIRECTION BUT TRACK SPEEDS ARE FAIRLY 
CONSISTENT. INTENSITY FORECAST GUIDANCE IS IN GOOD AGREEMENT WITH THE 
OVERALL SCENARIO, SUPPORTING, WITH THE EXCEPTION OF THE LATEST HAFS 
RUN, NEAR-TERM INTENSIFICATION FOLLOWED BY SLOW BUT STEADY WEAKENING 
AFTER TAU 36. COAMPS-TC CAPS THE GUIDANCE AT A PEAK OF 60 KTS BETWEEN 
TAU 24 AND 36.

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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