WDPN32 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (BAILU) WARNING 
NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 39.4N 159.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 857 NM EAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH WEAK CONVECTION
DRIFTING EASTWARD WHILE UNDER THE MID-LATITUDE WESTERLIES.
STRATOCUMULUS WRAPS INTO TROPICAL DEPRESSION (TD) 13W AROUND THE
NORTHERN AND WESTERN SIDE. THE PRESENCE OF SC IS AN INDICATOR THAT
EXTRATROPICAL TRANSITION IS UNDER WAY ALONG WITH OTHER FACTORS,
SUCH AS HIGH VERTICAL WIND SHEAR (VWS) FROM AN APPROACHING
UPPER-LEVEL TROUGH AND LOW SEA SURFACE TEMPERATURES. CURRENTLY, THE
TD IS UNDER AN UPPER-LEVEL RIDGE AND LIES SOUTH OF THE BAROCLINIC
ZONE. A COOPERATIVE INSTITUTE FOR RESEARCH IN THE ATMOSPHERE (CIRA)
AMSU-DERIVED AZIMUTHALLY AVERAGED TEMPERATURE AND HEIGHT CROSS
SECTION PRODUCT IDENTIFIES A WARM-CORE SYSTEM DESPITE A LOSS OF
TROPICAL CHARACTERISTICS SUCH AS A SYMMETRICAL WIND FIELD AND DEEP
CONVECTION. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE EXPOSED LLCC IN ANIMATED EIR. THE INITIAL INTENSITY OF
30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A 051057Z METOP-C
ASCAT IMAGE REVEALING THE LLCC SURROUNDED BY 25-30KT WINDS TO THE
SOUTH OF THE LLCC.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T2.0 - 30 KTS
   RCTP: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 29 KTS AT 051130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 19-20 CELSIUS
   OUTFLOW: WEAK EASTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST LENGTH HAS BEEN
TRUNCATED TO 24 HOURS.

FORECAST DISCUSSION: TD 13W WILL CONTINUE TO TRACK NORTHEASTWARD
WHILE STEERED ON THE LOW-LEVEL FLOW BY A SUBTROPICAL RIDGE TO THE
SOUTHEAST. THE SYSTEM WILL ACQUIRE COLD-CORE CHARACTERISTICS DURING
THE NEXT TWELVE HOURS AS THE UPPER-LEVEL TROUGH APPROACHES THE TD.
THE SYSTEM WILL BECOME FRONTAL DUE TO BAROCLINIC FORCING AND
THERMAL ADVECTION, RESULTING IN A FULLY EXTRATROPICAL SYSTEM BY THE
END OF THE FORECAST. TD 13W WILL WEAKEN OVER THE NEXT 12 HOURS DUE
TO HIGH VERTICAL WIND SHEAR AND A LACK OF THERMAL SUPPORT. BY TAU
24, TD 12W WILL BE CLASSIFIED AS A 25KT EXTRATROPICAL CYCLONE, BUT
BAROCLINIC FORCING MAY RESULT IN INTENSIFICATION BEYOND THE
FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG
AGREEMENT THAT TD 13W WILL TRACK NORTHEASTWARD FOR THE REMAINDER OF
THE FORECAST PERIOD. THE CROSS-TRACK SPREAD AT TAU 24 IS 40NM. THE
INTENSITY GUIDANCE HAS A NOTABLE SPREAD BETWEEN HAFS-A AND GFS
INTENSIFYING IN THE NEXT 12-24 HOURS, WHILE COAMPS-TC(GFS) AND
COAMPS-TC(NAVGEM) BOTH FORECAST RAPID WEAKENING. BEYOND THE
FORECAST PERIOD, IT IS POSSIBLE THAT THE SYSTEM MAY RE-INTENSIFY
DUE TO BAROCLINIC FORCING. THE TIMING OF EXTRATROPICAL TRANSITION
MAY VARY, AND THE FSU CYCLONE PHASE GUIDANCE INDICATES A TRANSITION
EARLIER THAN IN PREVIOUS MODEL RUNS.

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