WDPN31 PGTW 012100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
037//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 35.2N 141.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 75 NM EAST-SOUTHEAST OF NARITA AIRPORT
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS NEARLY
FULLY EXPOSED, RAGGED LOW-LEVEL CIRCULATION CENTER (LLCC) OF
TROPICAL STORM (TS) 12W (KROSA). ENVIRONMENTAL ANALYSIS REVEALS
MARGINALLY FAVORABLE CONDITIONS CHARACTERIZED BY WARM (27-28 C) SEA
SURFACE TEMPERATURES (SST), LOW (5-10 KTS) VERTICAL WIND SHEAR
(VWS) AND MODERATE POLEWARD OUTFLOW ALOFT, OFFSET BY INCREASING DRY 
AIR ENTRAINMENT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON THE ANIMATED SHORTWAVE INFRARED SATELLITE IMAGERY, SUPPORTED 
BY A 011800Z PROXYVIS IMAGE. THE INITIAL INTENSITY OF 55 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A 011555Z GCOMW1 AMSR2 WIND 
SPEED PRODUCT SHOWING WIND SPEEDS OF 50-55 KTS WITHIN THE 
SOUTHEASTERN QUADRANT OF THE CIRCULATION, AS WELL AS THE AGENCY 
DVORAK AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: A 011555Z GCOMW1 AMSR2 WIND SPEED DATA

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 54 KTS AT 011600Z
   CIMSS ADT: 34 KTS AT 011830Z
   CIMSS AIDT: 42 KTS AT 011830Z
   CIMSS D-MINT: 57 KTS AT 011642Z
   CIMSS D-PRINT: 53 KTS AT 011830Z

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

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 IS FORECAST TO TRACK EAST-NORTHEASTWARD
UNDER THE PRIMARY INFLUENCE OF A DEEP-LAYER STR CENTERED TO THE
SOUTHEAST. WHILE THE SYSTEM IS TRANSITING OVER WARM WATERS OF THE
KUROSHIO CURRENT, IT HAS POTENTIAL FOR SLIGHT INTENSIFICATION OVER
THE NEXT 24 HOURS, OR AT LEAST MAINTAIN INTENSITY. AFTER TAU 24,
INCREASINGLY HOSTILE ENVIRONMENT, INCLUDING INCREASING VWS, COOLING
SST AND CONTINUOUS DRY AIR ENTRAINMENT WILL RESULT IN GRADUAL 
WEAKENING. AROUND TAU 48 HOWEVER, TS 12W IS EXPECTED TO BEGIN
INTERACTING WITH THE BAROCLINIC ZONE TO THE NORTH, AS THE SYSTEM 
APPROACHES AND EVENTUALLY MERGES WITH A DEEP-LAYER WESTERLY FLOW. TS 
KROSA WILL WEAKEN TO 30 KTS AS IT COMPLETES EXTRATROPICAL TRANSITION 
BY TAU 72.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT THROUGHOUT THE FORECAST PERIOD, AS WITNESSED BY A SUB-100
NM CROSS-TRACK SPREAD AT TAU 72. ALONG-TRACK SPREAD IS ALSO IN GOOD
AGREEMENT THROUGH THE INITIAL 36-48 HOURS, HOWEVER THE TRANSLATION
SPEED UNCERTAINTY INCREASES AFTERWARDS. IN REGARD TO INTENSITY,
MODEL GUIDANCE IS IN FAIR AGREEMENT, WITH ALL MODELS INDICATING
WEAKENING AFTER TAU 24. PRIOR TO THAT HOWEVER, GFS INDICATES
POTENTIAL FOR SLIGHT INTENSIFICATION (UP TO 60 KTS PEAK), WHILE
OTHER MODELS (COAMPS-TC, HAFS, STATISTICAL-DYNAMICAL) INDICATE SLOW 
WEAKENING BEGINNING IMMEDIATELY. JTWC FORECAST IS LAID WITH MEDIUM 
CONFIDENCE, WITHIN 5 KTS, ON THE HIGHER SIDE OF THE MULTI-MODEL 
CONSENSUS THROUGHOUT THE FORECAST PERIOD.

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