WDXS31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 21S (OLGA) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.3S 119.7E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 576 NM NORTHEAST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:ANIMATED 
ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS TC 21S RAPIDLY 
CONSOLIDATED WITH FEEDER BANDS WRAPPING TIGHTER TOWARD A RUGGED 14-NM 
EYE. A STRONG POLEWARD OUTFLOW PERSISTS AS EVIDENCED BY EXTENSIVE 
CIRRUS STREAKS ALONG THE SOUTHERN PERIPHERY. THE INITIAL POSITION IS 
PLACED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE IN THE EIR LOOP. 
THE INITIAL INTENSITY IS ALSO PLACED WITH HIGH ONFIDENCE BASED ON THE 
HIGH END OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE 6-
HR CONVECTIVE AND WRAP IMPROVEMENT. ANALYSIS INDICATES A FAVORABLE 
ENVIRONMENT WITH MODERATE VWS, STRONG OUTFLOW, AND WARM SST SLIGHTLY 
OFFSET BY DRY AIR INTRUSION AT THE LOW LEVELS ALONG THE WESTERN 
PERIPHERIES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: SOUTHWEST EXTENSION OF THE DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS SATCON: 59 KTS AT 061644Z
   CIMSS ADT: 57 KTS AT 061730Z
   CIMSS DPRINT: 59 KTS AT 061800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TC 21S WILL TRACK MORE SOUTHWESTWARD ALONG THE
NORTHWEST EDGE OF THE SOUTHWEST EXTENSION OF THE STEERING STR. THE
FAVORABLE ENVIRONMENT WILL FUEL FURTHER INTENSIFICATION TO A PEAK
OF 80KTS BY TAU 12. AFTERWARD, INCREASING COLD DRY AIR INTRUSION AT
THE LOWER LEVELS, THEN LATER ON, INCREASING VWS AS THE CYCLONE
APPROACHES THE JET LEVEL WINDS ASSOCIATED WITH THE PREVAILING
WESTERLIES WILL COMBINE TO GRADUALLY WEAKEN THE SYSTEM LEADING TO 
DISSIPATION BY TAU 96.  

MODEL DISCUSSION: NUMERICAL WEATHER PREDICTION MODELS ARE IN
OVERALL GOOD AGREEMENT WITH NAVGEM THE SOLE LEFT OUTLIER TRACKING THE 
VORTEX DEEP INTO THE STR TOWARD THE CENTRAL WESTERN AUSTRALIAN COAST. 
AN UNLIKELY SCENARIO. THE MAIN PACK GRADUALLY AND EVENLY SPREADS OUT 
TO A MERE 165NM BY TAU 72, LENDING HIGH CONFIDENCE TO THIS PORTION OF 
THE JTWC TRACK FORECAST THAT IS LAID JUST TO THE RIGHT OF CONSENSUS TO 
OFFSET NAVGEM. AFTERWARD, THE MODELS SIGNIFICANTLY DIVERGE ALONG- AND 
ACROSS-TRACK, AN INDICATION OF A WEAK VORTEX UNDERGOING DISSIPATION, 
LENDING LOW CONFIDENCE TO THE EXTENDED PORTION OF THE JTWC TRACK 
FORECAST.

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