WDPN31 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.5N 145.0E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 167 NM NORTH-NORTHWEST OF AGRIHAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS BUILDING
CENTRALIZED DEEP CONVECTION OVER THE LOW-LEVEL CIRCULATION CENTER
(LLCC). DRY AIR AND HIGH VERTICAL WIND SHEAR ASSOCIATED WITH A
TROUGH TO THE WEST IMPOSING ON THE STRUCTURE OF TROPICAL
STORM (TS) 11W. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON A 270558Z F-18 DMSP SSMIS 37GHZ MICROWAVE IMAGE
HIGHLIGHTING THE ERODED LOW-LEVEL CIRCULATION IN COMPARISON TO THE
SYMMETRIC MICROWAVE EYE EVIDENT ON THE 91GHZ IMAGE. THE DIFFERENCE
BETWEEN THE TWO SYSTEMS ALSO INDICATES A VERTICAL TILT WITH HEIGHT
GIVEN THAT THE MICROWAVE EYE IN THE UPPER LEVEL IS POSITIONED EAST
OF THE LLCC. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH LOW
CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A NEAR EQUATORIAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 37 KTS AT 270257Z
   CIMSS ADT: 55 KTS AT 270530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 WILL CONTINUE TRACKING NORTHWARD ON THE
NEAR EQUATORIAL RIDGE TO THE EAST THROUGH TAU 48. THE STEERING
ENVIRONMENT WILL BECOME WEAK AND COMPETING BETWEEN THE NEAR
EQUATORIAL RIDGE AND A SUBTROPICAL RIDGE CENTERED OVER JAPAN. THE
NEAR EQUATORIAL RIDGE WILL REORIENT ON A SOUTHWEST-NORTHEAST RIDGE
AFTER TAU 72, ALLOWING THE SYSTEM TO DRIVE NORTHWESTWARD FOR THE
REMAINDER OF THE FORECAST PERIOD. THE SYSTEM WILL CONTINUE TO
COMBAT HIGHLY UNFAVORABLE VERTICAL WIND SHEAR WITH EXPANSIVE
DUAL-CHANNEL OUTFLOW FOR THE NEXT 24 HOURS. AFTER TAU 36, VERTICAL
WIND SHEAR WILL INCREASE UNFAVORABLY AND ENTRAIN DRY AIR INTO THE
CORE OF THE SYSTEM. THE QUASI-STATIONARY MOTION WILL DRAIN THE
OCEAN HEAT CONTENT AS WELL, BUT AFTER TAU 72 THE SYSTEM WILL MOVE
INTO WARMER FAVORABLE WATERS AND REINTENSIFY TO 80KTS BY THE END OF
THE FORECAST.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
IN THE NEAR-TERM FORECAST, BUT BECOMES IRREGULAR BETWEEN TAU 36-72.
THE SPREAD IS 157NM BY TAU 72. FOLLOWING TAU 72, THE MULTI-MODEL
CONSENSUS MEMBERS AGREE ON A NORTHEASTWARD TRACK WITH A SIMILAR
SPREAD THROUGH THE END OF THE FORECAST. THE INTENSITY GUIDANCE IS
INDICATES PEAK INTENSITIES BETWEEN 70KTS AT TAU 24 TO 45KTS AT TAU
24. THUS, THERE ARE VARYING SOLUTIONS BETWEEN THE MULTI-MODEL
GUIDANCE. THE JTWC RI GUIDANCE INDICATES A STRONG POSSIBILITY OF
RAPID INTENSIFICATION WITHIN THE FIRST 24 HOURS OF THE FORECAST,
WHICH IS WHY THE PEAK AT TAU 24 LIES ABOVE THE CONSENSUS MEAN.

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