WDPN32 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.4N 146.0E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 359 NM EAST-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A MIDGET
SYSTEM THAT CONTINUES TO STRUGGLE WITH FLARING CONVECTION PARTLY
OBSCURING THE LOW-LEVEL CIRCULATION (LLC). WATER VAPOR IMAGERY REVEALS 
WEAK RADIAL OUTFLOW, EXACERBATED BY SUBSIDENCE ALONG THE SOUTHERN 
FLANK CAUSED BY A TUTT CELL TO THE SOUTHWEST. THE INITIAL POSITION IS 
PLACED WITH HIGH CONFIDENCE BASED ON A DEFINED LLCC FEATURE IN THE 
042328Z GPM 89GHZ IMAGE AND LINED UP WITH THE LLC BECOMING MOMENTARILY 
EXPOSED IN VISIBLE SATELLITE IMAGERY FROM 042240Z-042320Z. THE INITIAL 
INTENSITY OF 25 KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON 
IDENTICAL DVORAK ESTIMATES FROM ALL THREE REPORTING AGENCIES AND 
REFLECTS THE SUSTAINED 6-HR CONVECTIVE SIGNATURE. ANALYSIS INDICATES A 
MARGINALLY FAVORABLE ENVIRONMENT WITH WARM SST, LIGHT VWS, AND WEAK 
RADIAL OUTFLOW OFFSET BY SUBSIDENCE AND COOL DRY AIR INTRUSION AT THE 
LOW LEVELS.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 34 KTS AT 042330Z
   CIMSS DMNT: 25 KTS AT 042328Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TD 13W HAS CRESTED THE STR AXIS AND WILL TRACK
MORE NORTH-NORTHEASTWARD THEN ACCELERATE NORTHEASTWARD AS IT ROUNDS
THE POLEWARD SIDE OF THE STEERING STR. THE MARGINALLY FAVORABLE
ENVIRONMENT WILL FUEL A SLIGHT INTENSIFICATION TO 30KTS AT TAUS
12-24. AFTERWARD, INCREASING VWS, SUSTAINED SUBSIDENCE ALOFT, AND
COOL DRY AIR INTRUSION NEAR THE SURFACE WILL REDUCE IT BACK TO
25KTS AND INHIBIT ANY FURTHER INTENSIFICATION. CONCURRENTLY BY TAU
36, THE SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AND BY
TAU 48, WILL TRANSFORM INTO A COLD CORE LOW. THERE IS ALSO A DISTINCT 
POSSIBILITY THAT TD 13W WILL DISSIPATE PRIOR TO COMPLETION OF ETT.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH AN
EVEN SPREAD TO A MERE 75NM BY TAU 48, LENDING HIGH CONFIDENCE IN
THE JTWC TRACK FORECAST. GIVEN THE VARIABILITY ASSOCIATED WITH ETT
AND THE POSSIBILITY OF AN EARLY DISSIPATION, THERE IS ONLY MEDIUM
CONFIDENCE IN THE JTWC INTENSITY FORECAST. 


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