WDPN31 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
041//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 39.0N 147.9E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 320 NM EAST-SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH
TROPICAL STORM (TS) 12W (KROSA). THE INITIAL POSITION IS ESTIMATED
WITH HIGH CONFIDENCE BASED ON THE ANIMATED VISIBLE SATELLITE IMAGERY
THAT SHOWS SPIRALING CONVECTIVE BANDS INTERSECTED WITH DRY AIR
INTRUSION INTO THE CORE OF THE SYSTEM. THE INITIAL INTENSITY IS
ASSESSED AT 55 KTS WITH HIGH CONFIDENCE, DERIVED FROM AVAILABLE
DVORAK AGENCY FIXES AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW,
AS WELL AS A 021322Z OSCANSAT-3 SCAT PASS, WHICH SHOWS A SWATH OF
45-50 KT WINDS TO THE SOUTH OF THE LLCC. ENVIRONMENTAL CONDITIONS
INDICATE A RAPIDLY DETERIORATING ENVIRONMENT, WITH COOLING SEA
SURFACE TEMPERATURES (SST) RANGING FROM 24-25 C, INCREASING AND
MODERATE VERTICAL WIND SHEAR (VWS) OF 15-20 KTS, AS WELL AS DRY AIR
ENTRAINMENT WITHIN THE CIRCULATION. STRONG POLEWARD OUTFLOW ALOFT IS 
THE ONLY CURRENTLY OFFSETTING FACTOR.

INITIAL WIND RADII BASIS: A 021322Z OSCANSAT-3 SCAT PASS

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
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 58 KTS AT 021622Z
   CIMSS ADT: 35 KTS AT 021730Z
   CIMSS AIDT: 59 KTS AT 021730Z
   CIMSS D-MINT: 51 KTS AT 021640Z
   CIMSS D-PRINT: 54 KTS AT 021830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 12W IS EXPECTED TO TRACK EAST-NORTHEASTWARD
UNDER THE INFLUENCE OF A DEEP-LAYER SUBTROPICAL RIDGE LOCATED TO
THE SOUTHEAST. THE SYSTEM IS CURRENTLY POSITIONED WELL NORTH OF THE
KUROSHIO CURRENT, RESULTING IN DRAMATICALLY COOLING SST. 
ADDITIONALLY, VERTICAL WIND SHEAR IS NOT ONLY INCREASING, BUT IS 
BEGINNING TO DESTRUCTIVELY INTERFERE WITH THE MOTION VECTOR OF TS 
KROSA. AS A RESULT, THE SYSTEM IS FORECAST TO BEGIN GRADUAL 
WEAKENING, ENHANCED BY INCREASINGLY HOSTILE ENVIRONMENTAL PARAMETERS 
AS
MENTIONED EARLIER. BY TAU 36, TS 12W IS EXPECTED TO BEGIN INTERACTING 
WITH A BAROCLINIC ZONE TO THE NORTH AND MERGE WITH A DEEP-LAYER 
WESTERLY FLOW, BEGINNING ITS EXTRATROPICAL TRANSITION. INTENSITY IS 
FORECAST TO DIMINISH TO 35 KTS BY TAU 48, AS THE EXTRATROPICAL 
TRANSITION IS EXPECTED TO BE COMPLETE.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE SHOWS STRONG
CONSENSUS THROUGH THE FORECAST PERIOD, WITH A CROSS-TRACK SPREAD OF
APPROXIMATELY 100 NM AT TAU 48 AND ALONG-TRACK SPREAD OF 120 NM.
INTENSITY GUIDANCE ALSO REMAINS IN GOOD AGREEMENT, HOWEVER GFS AND
NAVGEM DRIVEN COAMPS-TC DEPICT THE MOST AGGRESSIVE WEAKENING.
THIS WILL RESULT IN COMPLETE DISSIPATION WITHIN 24 HOURS WHILE OTHER
MEMBERS OF THE CONSENSUS PRESENT A MORE CONSERVATIVE APPROACH. JTWC
INTENSITY FORECAST IS THEREFORE ISSUED WITH MEDIUM CONFIDENCE AND
IS LAID CLOSE TO THE MULTI-MODEL INTENSITY ENVELOPE.

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