WDPN31 PGTW 300900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.9N 143.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 123 NM NORTH-NORTHEAST OF CHICHI JIMA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SYMMETRIC
TROPICAL STORM (TS) WITH PERSISTENT CONVECTION EMBEDDED WITHIN A
LARGE EXPANSE OF DRY AIR. CONVECTION APPEARS TO HAVE BUILT OVER THE
LAST SIX HOURS AS THE SYSTEM HAS SLOWLY TRACKED NORTHEASTWARD INTO
SLIGHTLY WARMER WATERS. HOWEVER, THE 26C DEPTH IS SHALLOW, AND THE
IMPROVED STRUCTURE MAY NOT CONTINUE IF THE SYSTEM BECOMES SLOW AND
QUASI-STATIONARY. AN EARLIER 290404Z GCOM W-1 AMSR2 37GHZ MICROWAVE
IMAGE REVEALS THE SYMMETRIC LOW-LEVEL STRUCTURE, WHILE THE
UPPER-LEVEL ENVIRONMENT IS BROKEN AND RAGGED. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED ANIMATED
MSI. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON AN EARLIER 300404Z AMSR2 IMAGE REVEALING 40KTS
MAX IN TEH SOUTHEAST QUADRANT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN
A DEEP-LAYER RIDGE OVER JAPAN AND THE SOUTHWESTERLY MONSOONAL FLOW
TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 47 KTS AT 300343Z
   CIMSS ADT: 35 KTS AT 300540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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 HAS TRACKED SLOWLY NORTHEASTWARD OVER
THE LAST SIX HOURS, AND THE TRACK WILL REMAIN IRREGULAR AND SLOW
WHILE IN A COMPETING STEERING ENVIRONMENT BETWEEN THE SUBTROPICAL
RIDGE OVER JAPAN AND MONSOONAL FLOW TO THE SOUTH. GRADUALLY OVER
THE NEXT 36 HOURS THE RIDGE OVER JAPAN WILL WEAKEN AND THE TS WILL
CURVE NORTHEASTWARD. DURING THIS TIME, A VORTICITY MAXIMUM
APPROACHING FROM THE SOUTHWEST MAY RESULT IN MODERATE BINARY
INTERACTION, PRODUCING IRREGULARITY IN THE TRACK AS IT CURVES
NORTHWESTWARD AT TAU 48. A BUILDING NEAR EQUATORIAL RIDGE TO THE
SOUTHEAST WILL CAUSE THE SYSTEM TO CURVE NORTHEASTWARD AFTER TAU
48. THE SYSTEM WILL GRADUALLY INTENSIFY WHILE MOVING NORTHWARD,
LEAVING A COOL WAKE BEHIND DUE TO LOW OCEAN HEAT CONTENT (OHC). ANY
QUASI-STATIONARY PERIOD WITHIN THE FORECAST WILL DRAIN THE OHC IN
THE OCEAN BELOW THE SYSTEM AS THE 26C DEPTH IS SHALLOW.
ADDITIONALLY, A COLD EDDY SOUTH OF JAPAN WILL INHIBIT
INTENSIFICATION. SEA SURFACE TEMPERATURES WILL WARM AS THE SYSTEM
APPROACHES THE KUROSHIO CURRENT, LEADING TO A PEAK INTENSITY OF
60KTS AT TAU 72. TS 12W WILL WEAKEN AS THE SYSTEM TRACKS
NORTHEASTWARD AFTER TAU 72 DUE TO COOL WATERS NORTH OF THE KUROSHIO
CURRENT AND INCREASING VERTICAL WIND SHEAR.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE LEADS TO SIGNIFICANT
UNCERTAINTY IN THE TRACK GUIDANCE. THE JTWC MULTI-MODEL CONSENSUS
MEMBERS FAN OUT WITH A LARGE SPREAD AND VARYING ANGLES WHICH THE
SYSTEM WILL TRACK BETWEEN WEST-NORTHWEST AND NORTH-NORTHWEST. THE
ENSEMBLE GUIDANCE FOLLOWS SUIT WITH SIGNIFICANT UNCERTAINTY BETWEEN
BOTH GEFS AND ECENS. THE CURVE WEST-NORTHWESTWARD IS LIKELY
ASSOCIATED WITH VARYING STRENGTH OF BINARY INTERACTION WITH THE
VORTICITY MAXIMUM EMBEDDED WITHIN THE MONSOONAL FLOW. THE INTENSITY
FORECAST IS MADE WITH LOW CONFIDENCE DUE TO THE SIGNIFICANT TRACK
VARIATION.

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