WDPN31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
038//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 36.4N 142.6E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 115 NM EAST-NORTHEAST OF NARITA AIRPORT
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH
TROPICAL STORM (TS) 12W (KROSA). THE INITIAL POSITION IS DETERMINED
WITH MEDIUM CONFIDENCE UTILIZING ANIMATED VISIBLE SATELLITE IMAGERY
SHOWING SPIRAL BANDS OF DEEP CONVECTION INTERLACED WITH DRY AIR
ENTRAINING INTO THE CORE OF THE VORTEX. THE INITIAL INTENSITY IS
ESTIMATED AT 55 KTS WITH MEDIUM CONFIDENCE BASED ON AVAILABLE
DVORAK AGENCY FIXES AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. 
ENVIRONMENTAL ASSESSMENT INDICATES MARGINAL CONDITIONS FOR 
DEVELOPMENT WITH BORDERLINE (26-27 C) SEA SURFACE TEMPERATURES (SST), 
LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), AND MODERATE POLEWARD 
OUTFLOW ALOFT, PARTIALLY OFFSET BY INCREASING DRY AIR INTRUSION INTO 
THE CIRCULATION.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 51 KTS AT 020030Z
   CIMSS ADT: 34 KTS AT 020010Z
   CIMSS AIDT: 42 KTS AT 020010Z
   CIMSS D-MINT: 54 KTS AT 012353Z
   CIMSS D-PRINT: 48 KTS AT 020010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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 IS FORECAST TO CONTINUE MOVING
EAST-NORTHEASTWARD UNDER THE INFLUENCE OF A DEEP-LAYER STR CENTERED
TO THE SOUTHEAST. THE SYSTEM IS CURRENTLY IN THE VICINITY OF THE
KUROSHIO CURRENT, WITH MAJORITY OF THE WINDFIELD TOWARD THE POLEWARD 
SIDE. THEREFORE, THE SYSTEM IS FORECAST TO MAINTAIN INTENSITY DURING 
THE NEXT 12 HOURS, UTILIZING THE WARM WATER INFLUX. BEYOND TAU 12, 
ENVIRONMENTAL CONDITIONS WILL DETERIORATE WITH INCREASING VWS, 
DECREASING SST, AND PERSISTENT DRY AIR ENTRAINMENT, LEADING TO A 
GRADUAL WEAKENING TREND. BY AROUND TAU 48, TS 12W IS EXPECTED TO 
BEGIN INTERACTION WITH A BAROCLINIC ZONE TO THE NORTH AND EVENTUALLY 
MERGE WITH A DEEP-LAYER WESTERLY FLOW, INITIATING EXTRATROPICAL 
TRANSITION. INTENSITY IS FORECAST TO DECREASE TO 30 KTS BY TAU 72 AS 
THE EXTRATROPICAL TRANSITION COMPLETES BY OR PRIOR TO TAU 72.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE SHOWS GOOD
CONSENSUS THROUGH THE FORECAST PERIOD, WITH A CROSS-TRACK SPREAD OF
LESS THAN 100 NM AT TAU 72. ALONG-TRACK SPREAD REMAINS TIGHT FOR
THE INITIAL 48 HOURS, WITH INCREASING UNCERTAINTY IN FORWARD SPEED
THEREAFTER. INTENSITY MODEL GUIDANCE AGREES ON WEAKENING PAST TAU
12, HOWEVER, THE GFS MODEL STILL SUGGESTS SLIGHT INTENSIFICATION
JUST BEFORE THEN. OTHER MODELS (COAMPS-TC, HAFS, AND
STATISTICAL-DYNAMICAL SUITE) FORECAST GRADUAL WEAKENING BEGINNING
IMMEDIATELY. JTWC OFFICIAL INTENSITY FORECAST IS ISSUED WITH MEDIUM
CONFIDENCE, PLACED ON THE HIGHER END OF THE MULTI-MODEL INTENSITY
ENVELOPE.

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