WDPN31 PGTW 302100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.3N 143.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 401 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SLIGHTLY
IMPROVED ORGANIZATION WITH A NEW CONVECTIVE BAND WRAPPING ALONG THE
NORTHERN PERIPHERY OF THE CIRCULATION. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON A CLEAR CENTER FEATURE EVIDENT
IN 301533Z GMI 37 GHZ IMAGERY AND 301800Z INFRARED IMAGERY. THE
INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON SUPPORTIVE MULTI-AGENCY SUBJECTIVE DVORAK VALUES AND A
UW-CIMSS AUTOMATED SATELLITE CONSENSUS ESTIMATE OF 46 KNOTS. THE
SYSTEM HAS STARTED A SLOW JOG POLEWARD OVER THE PAST SIX HOURS IN
RESPONSE TO BUILDING LOW- TO MID-LEVEL SUBTROPICAL RIDGING TO THE
EAST.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: BUILDING LOW- TO MID-LEVEL SUBTROPICAL
RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 46 KTS AT 301800Z
   CIMSS ADT: 32 KTS AT 301730Z
   CIMSS AIDT: 43 KTS AT 301730Z
   CIMSS D-MINT: 52 KTS AT 301611Z
   CIMSS D-PRINT: 52 KTS AT 301800Z

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

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: THE STEERING ENVIRONMENT IS EVOLVING NEAR TS
12W, WITH THE COMPETING INFLUENCES OF SUBTROPICAL RIDGING TO THE
NORTH AND MONSOONAL FLOW TO THE SOUTHWEST SLOWING GIVING WAY TO
FORCING FROM BUILDING SUBTROPICAL RIDGING TO THE EAST. THIS LOW- TO
MID-LEVEL RIDGING IS EXPECTED TO CONTINUE BUILDING AND REMAIN THE
PRIMARY STEERING INFLUENCE FOR THE NEXT 48 HOURS, CARRYING THE
SYSTEM GRADUALLY NORTHWESTWARD TOWARD THE SOUTHEASTERN COAST OF
HONSHU. THEREAFTER, A DEVELOPING SHORTWAVE TROUGH WILL WEAKEN THE
STEERING RIDGE AS IT OVERTAKES TS 12W FROM THE NORTHWEST, TURNING
THE SYSTEM NORTHEASTWARD. INTERACTION WITH A DEVELOPING DISTURBANCE
EMBEDDED IN THE MONSOON TROUGH TO THE SOUTHWEST COULD DEFLECT STORM
MOTION A BIT FARTHER TO THE WEST THROUGH TAU 48, ALTHOUGH THIS
INTERACTION APPEARS TO BE LESS LIKELY THAN PREVIOUSLY ASSESSED. THE
SYSTEM CENTER IS EXPECTED TO PASS SOUTHEAST OF HONSHU BETWEEN TAU
48 AND 72 AND ACCELERATE EAST-NORTHEASTWARD THEREAFTER AS IT ROUNDS
THE STEERING RIDGE AXIS. SLOW INTENSIFICATION IS EXPECTED IN THE
NEAR-TERM TO MEDIUM TERM AS THE SYSTEM MOVES OVER SLIGHTLY WARMER
WATER BUT UPPER-LEVEL OUTFLOW REMAINS LIMITED. IN THE EXTENDED
PERIOD, INCREASING VERTICAL WIND SHEAR AND PASSAGE OVER COOLER
WATER WILL WEAKEN THE SYSTEM AS IT BEGINS EXTRATROPICAL TRANSITION,
WHICH IS EXPECTED TO BEGIN AFTER TAU 96.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN BETTER AGREEMENT THIS
CYCLE, WITH THE MAJORITY OF BOTH DETERMINISTIC AND ENSEMBLE MODEL
SOLUTIONS KEEPING THE CENTER OF 12W OFFSHORE TO THE SOUTHEAST OF
HONSHU. HOWEVER, SOLUTIONS THAT DEPICT A SHARPER WESTWARD JOG IN
THE NEAR-TERM AND A BROADER TURN NORTHEASTWARD AFTER TAU 48 REMAIN
IN THE GUIDANCE PACKAGE, INDICATING THAT THERE IS STILL A
(DECREASING) CHANCE THAT THE CENTER WILL PASS OVER LAND.  OF NOTE,
THE GFS AND GEFS SOLUTIONS INDICATE STRONGER INTERACTION WITH THE
DEVELOPING DISTURBANCE TO THE SOUTHWEST AND CORRESPONDENT SHARPER
WESTWARD TRACK BEFORE THE SYSTEM CHECKMARKS TO THE NORTHEAST, WHILE
THE AIFS AND NAVGEM INDICATE BROADER AND SMOOTHER TURNS TO THE
NORTHEAST WITH MORE POTENTIAL FOR A CLOSER CPA TO THE KANTO PLAIN.
THE CURRENT FORECAST TRACK IS CONSISTENT WITH THE LATEST
MULTI-MODEL CONSENSUS. INTENSITY FORECAST GUIDANCE IS IN GOOD
AGREEMENT, WITH HAFS ON THE HIGH END INDICATING A 60 KNOT PEAK. THE
CURRENT INTENSITY FORECAST IS IN THE MIDDLE OF THE GROUPING AND
CONSISTENT WITH PREVIOUS FORECASTS, THOUGH SLIGHTLY STRONGER IN THE
EXTENDED RANGE.

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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