WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 34.3N 141.3E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 99 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS BUILDING
DEEP CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC)
OF TROPICAL STORM (TS) 12W. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE AFOREMENTIONED ANIMATED EIR AND WAS
SUPPLEMENTED BY RADAR IMAGERY DEPICTING CLOUD BANDING ENCIRCLING
THE LLCC. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH LOW
CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: A NEAR EQUATORIAL RIDGE (NER) TO THE
SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T4.5 - 77 KTS
   CIMSS SATCON: 57 KTS AT 010943Z
   CIMSS ADT: 37 KTS AT 011130Z
   CIMSS AIDT: 57 KTS AT 011130Z
   CIMSS D-MINT: 61 KTS AT 010819Z
   CIMSS D-PRINT: 59 KTS AT 011130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 12W WILL CURVE SLOWLY NORTHEASTWARD UNDER
THE STEERING INFLUENCE OF THE NEAR EQUATORIAL RIDGE TO THE
SOUTHEAST. AFTER TAU 12, AN APPROACHING DEEP LAYER-TROUGH FROM THE
NORTHWEST WILL INCREASE THE TRACK SPEED GRADUALLY OVER THE COURSE
OF THE FORECAST PERIOD, DRIVING THE SYSTEM NORTHEASTWARD. BETWEEN
TAU 36-48, TS 12W WILL UNDERGO EXTRATROPICAL TRANSITION AS THE
SYSTEM BECOMES BAROCLINIC AND FRONTAL. THE WARM WATERS OF THE
KUROSHIO CURRENT WILL SUPPORT A 60KT INTENSITY FOR THE NEXT 12
HOURS WHILE COUNTERED BY AN UNFAVORABLE UPPER-LEVEL ENVIRONMENT AND
DRY AIR ENTRAINING INTO THE CIRCULATION. AFTER TAU 12, HIGH
VERTICAL WIND SHEAR WILL INITIATE WEAKENING AND AMPLIFY THE
AFOREMENTIONED UNFAVORABLE FEATURES. BY THE END OF THE FORECAST, TS
12W WILL WEAKEN TO 50KTS AS AN EXTRATROPICAL CYCLONE.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
THAT TS 12W WILL ASSUME A NORTHEASTWARD TRACK FOR THE REMAINDER OF
THE FORECAST PERIOD, WITH THE EXCEPTION OF NAVGEM WHICH STANDS OUT
NORTH OF THE JTWC MULTI MODEL CONSENSUS. THE TRACK FORECAST IS
ASSESSED WITH MEDIUM CONFIDENCE WITH A CROSS-TRACK SPREAD OF 60NM
AT TAU 24 AND 50NM AT TAU 48, EXCLUDING THE OUTLIER OF NAVGEM. THE
INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT TS 12W WILL GRADUALLY
WEAKEN AFTER TAU 12 TO 45-50KTS AT THE END OF THE FORECAST PERIOD,
LEADING TO A MEDIUM CONFIDENCE IN THE INTENSITY FORECAST DEPENDING
ON THE RATE OF EXTRATROPICAL TRANSITION AND BAROCLINIC INFLUENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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