WDPN31 PGTW 290300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.4N 143.0E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 234 NM NORTH-NORTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 12W (KROSA) WITH AN INCREASINGLY OBSCURED LOW-LEVEL
CIRCULATION CENTER (LLCC) AS FLARING CONVECTION HAS BECOME
PREVALENT IN CLOSE PROXIMITY TO THE CENTER. WHILE ANIMATED VISIBLE
IMAGERY HAS BECOME AVAILABLE, LOW-LEVEL CURVED CONVECTIVE CLOUD
LINES HAVE BEEN OBSERVED WRAPPING NEATLY BELOW THE AFOREMENTIONED
CENTRAL CONVECTION WITH INCREASINGLY ORGANIZED CURVED BANDING AROUND
THE SYSTEMS PERIMETER. ALOFT, WEAK EQUATORWARD OUTFLOW HAS BEEN
IDENTIFIED ON ANIMATED WATER VAPOR IMAGERY WITH CIRRIFORM
STRIATIONS WRAPPING ANTICYCLONICALLY AROUND THE SYSTEMS EASTERN
FLANK. WITH REGARD TO THE ENVIRONMENTAL ANALYSIS, LOW VERTICAL WIND
SHEAR (LESS THAN 15 KTS) AND WARM SEA SURFACE TEMPERATURES (26-27
C) ARE HELPING THE SYSTEM MAINTAIN 50 KTS INTENSITIES AT THE
SURFACE. THE INITIAL POSITION AND INTENSITY HAS BEEN ASSESSED WITH
HIGH CONFIDENCE BASED ON A RECENT 282334Z METOP-B ASCAT IMAGE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT, WEDGED
BETWEEN A DEEP-LAYERED SUBTROPICAL RIDGE LOCATED TO THE SOUTHEAST
AND AN ADDITION SUBTROPICAL RIDGE POSITIONED TO THE NORTHWEST OVER
CENTRAL JAPAN.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS ADT: 32 KTS AT 290130Z
   CIMSS AIDT: 36 KTS AT 290130Z
   CIMSS D-MINT: 40 KTS AT 282139Z
   CIMSS D-PRINT: 44 KTS AT 290130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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 FORECASTED TO CONTINUE ITS SLOW
TRACK TO THE NORTH-NORTHWEST THROUGHOUT THE DURATION OF THE 120
HOUR FORECAST PERIOD DUE TO THE ONGOING COMPLEX STEERING
ENVIRONMENT TO THE NORTH AND EAST. AS THE WELL-ENTRENCHED RIDGE
CONTINUES OVER CENTRAL JAPAN, THE NORTHWARD MOTION OF TS 12W WILL
SLOW THE EXPECTED NORTHWARD TRACK INTO TAU 120. AS THE SUBTROPICAL
RIDGE DIRECTLY TO THE NORTH FLUCTUATES IN ORIENTATION AND STRENGTH
OVER THE NEXT FEW DAYS, THE SPEED OF APPROACH AND DIRECTION OF TS
12W MAY SIGNIFICANTLY CHANGE AS THE DEEP-LAYERED SUBTROPICAL RIDGE
TO THE SOUTHEAST BUILDS WESTWARD. AS STATED PREVIOUSLY, THE TRACK
SPEED AND DIRECTION OF 12W IS HEAVILY RELIANT ON HOW THE
SUBTROPICAL RIDGE OVER CENTRAL JAPAN REORIENTS. IF THE
AFOREMENTIONED RIDGE OVER CENTRAL JAPAN BUILDS OVER THE NEXT 12-24
HOURS, MODEL TRACK SOLUTIONS TRACK TS KROSA NORTHWESTWARD TOWARD
THE EASTERN COAST OF HONSHU. IF THAT SAME RIDGE WEAKENS, TRACK
SOLUTIONS ARE EXPECTING MORE OF A NORTHEASTWARD APPROACH BETWEEN
TAU 72 AND TAU 96. WITH REGARD TO THE SYSTEMS INTENSITY, THE
CONTINUING SLOW APPROACH NORTHWARD HAS RESULTED IN SIGNIFICANT
UPWELLING, CAPPING INTENSITIES TO 50-55KTS THROUGH TAU 120.
ALTHOUGH VWS REMAINS LOW (LESS THAN 15 KTS), DRY AIR WILL LIMIT
SURFACE INTENSITIES TO 50 KTS, AND STEADILY INCREASE TO 55 KTS BY
TAU 72 AS THE CORE RE-MOISTENS INTO TAU 120.

MODEL DISCUSSION: NUMERICAL MODEL PREDICTION (NWP) TRACK GUIDANCE
IS IN POOR AGREEMENT THROUGHOUT THE ENTIRETY OF THE FORECAST
PERIOD. ALL JTWC CONSENSUS SOLUTIONS BIFURCATE AT TAU 0 AND REMAIN
DIVERGED THROUGH THE END OF THE FORECAST PERIOD. AT TAU 12, THE
CROSS-TRACK SPREAD IS 172 NM AND INCREASES SIGNIFICANTLY TO MORE
THAN 500 NM BY TAU 120. THEREFORE, THE JTWC TRACK FORECAST HAS BEEN
PLACED WITH LOW CONFIDENCE THROUGHOUT THE ENTIRETY OF THE FORECAST
DUE TO A CONTINUING DISAGREEMENT AMONGST JTWC CONSENSUS SOLUTIONS. THE
INTENSITY GUIDANCE HOWEVER WAS ASSESSED WITH MEDIUM CONFIDENCE, AS
THE MAJORITY OF SOLUTIONS ILLUSTRATE STEADY INTENSITIES BETWEEN
50-55 KTS INTO TAU 120. A NOTICEABLE OUTLIER IS THE GFS
DETERMINISTIC SOLUTION, WHICH SHOWS A STEADY WEAKENING PHASE
THROUGH TAU 12, AND A MODERATE INCREASE TO 65 KTS BY TAU 120. OF
NOTE, THE COAMPS-TC EPS INTENSITY PROBABILITY GUIDANCE ALSO
ILLUSTRATES STEADY INTENSITIES INTO TAU 48, BUT WITH A POTENTIAL
WINDOW FOR MODERATE INTENSIFICATION THEREAFTER. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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