WDPN31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (KROSA) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.5N 144.5E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 71 NM WEST-SOUTHWEST OF AGRIHAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION REBUILDING OVER THE LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH EXPANSIVE DEEP CONVECTION DRIFTING POLEWARD AND EQUATORWARD.
WATER VAPOR IMAGERY REVEALS A TROUGH INTRODUCING DRY AIR AND
15-20KT VERTICAL WIND SHEAR TO THE NORTH OF THE SYSTEM. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 261148Z METOP-B
ASCAT IMAGE CAPTURING THE LOW-LEVEL CIRCULATION CENTER. THE INITIAL
INTENSITY OF 50 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED ASCAT IMAGE AND AN EARLIER 261058Z METOP-C ASCAT
IMAGE CAPTURING THE FAR EASTERN PERIPHERY OF THE LLCC.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT
BETWEEN TWO NEAR EQUATORIAL RIDGES

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 45 KTS AT 260856Z
   CIMSS ADT: 35 KTS AT 261130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND 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: TROPICAL STORM (TS) 12W IS FORECAST TO TRACK
NORTHWARD FOR THE NEXT 36 HOURS ON THE WESTERN PERIPHERY OF A NEAR
EQUATORIAL RIDGE TO THE EAST. BETWEEN TAU 36-48, THE STEERING
ENVIRONMENT WILL BECOME COMPLEX BETWEEN THE NEAR EQUATORIAL RIDGE
TO THE EAST AND THE BUILDING SUBTROPICAL RIDGE TO THE NORTHWEST.
AFTER TAU 72, THE RIDGE TO THE SOUTHEAST WILL REORIENT ON AT
SOUTHWEST-NORTHEAST AXIS, DRIVING TS 12W NORTHEASTWARD FOR THE
REMAINDER OF THE FORECAST PERIOD. THE SYSTEM WILL REMAIN IN A
HIGHLY SHEARED ENVIRONMENT FOR THE FIRST 24 HOURS OF THE FORECAST
PERIOD, STAGNATING THE RATE OF INTENSIFICATION. THE SYSTEM WILL
SLOWLY INTENSIFY FOR THE REMAINDER OF THE FORECAST AS THE SHEAR
GRADUALLY DECREASES AND THE UPPER-LEVEL ENVIRONMENT REMAINS
STRONGLY DIVERGENT. ULTIMATELY, THE SYSTEM WILL PEAK AT 70KTS AT THE
END OF THE FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC GUIDANCE HAS SPREAD GRADUALLY OVER
THE LAST THREE MODEL RUNS BECOMING INCREASINGLY DIVERGENT AT TAU
72. THE CROSS-TRACK SPREAD AT THE END OF THE FORECAST IS 760NM WITH
NAVGEM TO THE WEST AND GEFS TO THE WEST. THE ENSEMBLE GUIDANCE
REPRESENTS A BIFURCATION SCENARIO IN BOTH GEFS AND ECENS. AS A
RESULT, THE TRACK FORECAST IS MADE WITH LOW CONFIDENCE. THE
INTENSITY GUIDANCE IS EQUALLY AS SPREAD AS THE TRACK GUIDANCE. GFS
DEPICTS A RAPID INTENSIFICATION SCENARIO TO A PEAK OF 80KTS WITHIN
THE FIRST 24 HOURS, WHILE HAFS-A REVEALS CONTINUOUS WEAKENING
THROUGHOUT THE ENTIRETY OF THE FORECAST PERIOD.

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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