WDXS31 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (FINA)       
WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.1S 130.6E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 30 NM NORTHWEST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 05S HAS TRACKED SLOWLY WEST-SOUTHWESTWARD
AWAY FROM SOUTHERN MELVILLE ISLAND. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY DEPICTS A WEAKENED EYE FEATURE AND GENERAL
WEAKENING OF THE CONVECTIVE STRUCTURE DUE TO THE INTERACTION WITH
LAND. HOWEVER, ANIMATED RADAR IMAGERY REVEALS SPIRAL BANDING
WRAPPING INTO A DEFINED EYE, WHICH SUPPORTS THE INITIAL POSITION
WITH HIGH CONFIDENCE. DUE TO THE RECENT TRACK MOTION, THE CENTER IS
ABOUT 25 NM NORTHWEST OF DARWIN AT 221200Z, WHICH IS REPORTING AN 
INCREASE IN SUSTAINED WINDS TO AS HIGH AS 40 KNOTS (10-MINUTE AVERAGE) 
AT 221030Z. SINCE 221030Z THE SUSTAINED WINDS HAVE DECREASED SLIGHTLY
WITH SLP INCREASING AS THE CENTER DRIFTS WEST-SOUTHWESTWARD (221409Z 
CENTER POSITION IS NEAR 12.19N 130.44E, APPROXIMATELY 30NM NORTHWEST 
OF DARWIN). RAINFALL AMOUNTS HAVE BEEN SIGNIFICANT WITHIN THE INTENSE 
RAINBANDS OVER THE SOUTHERN SEMICIRCLE, WITH ABOUT 6 INCHES REPORTED
AT THE DARWIN AIRPORT OVER THE PAST DAY. WITH EXCEPTION OF THE LAND
INTERACTION, ENVIRONMENTAL CONDITIONS ARE FAVORABLE, WITH ROBUST
POLEWARD OUTFLOW, MODERATE WESTWARD OUTFLOW, LOW VERTICAL WIND
SHEAR (VWS) AND WARM SST VALUES. THE INITIAL INTENSITY OF 85 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF THE SUBJECTIVE
AND OBJECTIVE INTENSITY ESTIMATES BUT HEDGED SLIGHTLY BELOW THE
RECENT 220944Z RCM3 SAR PASS INDICATING A VMAX OF 90 KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED TO THE SOUTHEAST, WITH RIDGE EXTENDING WESTWARD.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   ADRM: T5.5 - 102 KTS
   CIMSS ADT: 74 KTS AT 221200Z
   CIMSS AIDT: 66 KTS AT 221200Z
   CIMSS D-MINT: 69 KTS AT 220903Z
   CIMSS D-PRINT: 70 KTS AT 221200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: INTERACTION WITH LAND

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THE WESTERN EXTENSION OF THE STR IS FORECAST
TO WEAKEN WITH THE APPROACH OF A MAJOR SHORTWAVE TROUGH, WHICH WILL
ALLOW TC 05S TO TRACK SOUTHWESTWARD THROUGH TAU 36 OVER THE JOSEPH
BONAPARTE GULF. AFTER TRACKING AWAY FROM MELVILLE ISLAND, TC FINA
IS FORECAST TO BRIEFLY REINTENSIFY THROUGH TAU 12 UNDER FAVORABLE 
CONDITIONS TO A PEAK INTENSITY OF 95 KNOTS. INCREASING DRY AIR 
ENTRAINMENT AND HIGH (25 KNOTS) VWS WILL BEGIN TO WEAKEN THE SYSTEM 
NEAR TAU 24, WITH STEADY WEAKENING THROUGH TAU 36. AFTER TAU 36, TC 
05S WILL STEER AT A LOWER LEVEL, WITH A MORE WESTWARD TRACK ALONG THE 
NORTHERN PERIPHERY OF A LOW- TO MID-LEVEL STR TO THE SOUTH. RAPID 
WEAKENING WILL OCCUR DUE TO EXTENSIVE DRY AIR ADVECTING OFF AUSTRALIA, 
WITH DISSIPATION EXPECTED BY TAU 96. 

MODEL DISCUSSION: DETERMINISTIC GUIDANCE IS IN GOOD AGREEMENT THROUGH 
ONLY TAU 24, WITH A LARGE SPREAD AND INCREASING UNCERTAINTY AFTER TAU 
72. THE 220600Z GEFS AND EPS RUNS ALSO INDICATE LARGE SPREAD AND HIGH 
UNCERTAINTY. INTENSITY GUIDANCE HAS COME INTO BETTER AGREEMENT WITH 
THE BULK OF THE GUIDANCE NOW INDICATING STEADY WEAKENING INCLUDING THE 
220600Z HAFS-A RUN, WHICH SHOWS DRY AIR ENTRAINMENT STARTING IN THE 
NEXT 12-24 HOURS. THE 220600Z GFS RUN CONTINUES TO SHOW RAPID 
WEAKENING OVER THE NEXT DAY. HWRF DOES INDICATE REINTENSIFICATION, 
WITH A PEAK INTENSITY OF 97 KNOTS AT TAU 24.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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