WDPN31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
035//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.7N 141.3E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 124 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS EXPANSIVE
DEEP CONVECTION FLOWING POLEWARD AND OBSCURING THE LOW-LEVEL
CIRCULATION CENTER (LLCC) OF TROPICAL STORM (TS) 12W. AN
UPPER-LEVEL CYCLONE SOUTHWEST OF THE SYSTEM APPLIES PRESSURE ON THE
SOUTHERN SIDE, RESULTING IN FRAGMENTED LOW-LEVEL BANDING
IDENTIFIABLE ALONG THE SOUTHERN PERIPHERY OF TS 12W IN A 010632Z
DMSP F-18 SSMIS 37GHZ MICROWAVE IMAGE. THE 91GHZ IMAGE REVEALS A
POLEWARD TILT IN THE UPPER-LEVEL ENVIRONMENT DUE TO THE
SOUTHWESTERLY UPPER-LEVEL FLOW. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE AFOREMENTIONED ANIMATED MSI AND THE
SHARP CURVE OF LOW-LEVEL BANDING ON THE NORTHERN PERIPHERY OF THE
LLCC ON THE 37GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON PERSISTENCE FROM AN
EARLIER 010101Z METOP-C ASCAT IMAGE REVEALING 50-55KT WINDS IN THE
NORTHEASTERN QUADRANT OF THE SYSTEM WITH THE AGENCY AND OBJECTIVE
FIXES LISTED BELOW TAKEN INTO CONSIDERATION.

INITIAL WIND RADII BASIS: EARLIER 010101Z METOP-C SCATTEROMETER
DATA 

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
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 50 KTS AT 010306Z
   CIMSS ADT: 35 KTS AT 010530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG 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: TS 12W WILL CURVE NORTH-NORTHEASTWARD FOR THE
NEXT 12 HOURS UNDER THE STEERING INFLUENCE OF A NER TO THE
SOUTHEAST. BETWEEN TAU 24-36, THE SYSTEM WILL BEGIN TO CURVING
NORTHEASTWARD AFTER BECOMING EMBEDDED WITHIN A DEEP-LAYER TROUGH TO
THE NORTH WHICH WILL ENHANCE TRACK SPEED. THE SYSTEM WILL ENTER THE
BAROCLINIC ZONE BETWEEN TAU 48-72, FORCING EXTRATROPICAL TRANSITION
AND CAUSE 12W TO BECOME FULLY EXTRATROPICAL BY TAU 72. TS 12W
SYSTEM WILL SLIGHTLY INTENSIFY WHILE TRACKING OVER A WARM EXTENSION
OF THE KUROSHIO CURRENT NORTHWARD. AS THE SYSTEM ADVANCES
NORTHEASTWARD AFTER TAU 12, GRADUAL WEAKENING IS EXPECTED AS THE
SYSTEM PASSING INTO COOL WATER AND VERTICAL WIND SHEAR INCREASES
UNFAVORABLY OVER AFTER TAU 36. BY THE END OF THE FORECAST PERIOD,
THE SYSTEM WILL WEAKEN TO 35KTS AS AN EXTRATROPICAL CYCLONE.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG
AGREEMENT IN THE EARLY-TERM TRACK GUIDANCE WITH A CROSS-TRACK
SPREAD OF 40NM BY TAU 24. THE LATE TERM FORECAST GUIDANCE IS IN
MODERATE AGREEMENT WITH A CROSS-TRACK SPREAD OF 202NM BY TAU 72.
THE ENSEMBLE GUIDANCE IS ALSO CONSISTENT FORECASTING A GENERALLY
NORTHEASTWARD TRACK WITH ONLY ONE GEFS MEMBER AND ONE ECENS MEMBER
MAKING LANDFALL ON THE SOUTHEASTERN MOST TIP OF HONSHU. THE JTWC
INTENSITY GUIDANCE IS IN STRONG AGREEMENT THAT THE SYSTEM WILL
EITHER REACH A PEAK OF 60KTS PRIOR TO WEAKENING CONTINUOUSLY THROUGH
THE REMAINDER OF THE FORECAST PERIOD.

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