WDPN32 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (LEEPI) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 35.0N 146.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 354 NM EAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A SMALL
SYSTEM THAT CONTINUES TO STRUGGLE WITH FLARING CONVECTION OBSCURING
HALF OF THE LOW-LEVEL CIRCULATION (LLC). THE EIR LOOP ALSO SHOWS
WEAK RADIAL OUTFLOW AND COOL DRY AIR INTRUSION ALONG THE WESTERN
PERIPHERIES AS EVIDENCED BY STRATOCUMULUS CLOUD LINES WRAPPING
TOWARD THE LLC. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE PARTIALLY EXPOSED LLC IN THE EIR ANIMATION. THE INITIAL 
INTENSITY OF 35 KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
HIGH END OF AGENCY AND AUTOMATED DVORAK INTENSITIES AND SUPPORTED BY A 
051357Z OSCAT PASS THAT SHOWED 33-37KTS ALONG THE SOUTHEAST AND 
SOUTHWEST QUADRANTS. ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH 
WARM SST AND WEAK RADIAL OUTFLOW OFFSET BY HIGH VWS AND COOL DRY AIR 
INTRUSION AT THE LOW LEVELS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 051730Z
   CIMSS DPRNT: 36 KTS AT 051800Z
   CIMSS DMNT: 33 KTS AT 051629Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK RADIAL

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: TS LEEPI HAS CRESTED THE STR AXIS AND WILL
CONTINUE TO ACCELERATE NORTHEASTWARD ON THE POLEWARD SIDE OF THE
STEERING STR. THE MARGINAL ENVIRONMENT WILL REDUCE THE SYSTEM BACK TO 
A 30-KT TROPICAL DEPRESSION AND INHIBIT ANY FURTHER INTENSIFICATION. 
CONCURRENTLY BY TAU 24, THE SYSTEM WILL BEGIN EXTRA-TROPICAL 
TRANSITION (ETT) AND BY TAU 36, WILL TRANSFORM INTO A COLD CORE LOW. 
THERE IS ALSO A DISTINCT POSSIBILITY THAT TS 13W WILL DISSIPATE PRIOR 
TO COMPLETION OF ETT.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH AN
EVEN SPREAD TO A MERE 53NM BY TAU 36, 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//
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