WDXS31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (FINA)       
WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.9S 131.0E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 36 NM NORTH OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AS DEPICTED IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI), 
TROPICAL CYCLONE (TC) 05S HAS MAINTAINED A DEFINED CLOUD-FILLED EYE
WHILE TRACKING OVER THE SOUTHERN TIP OF MELVILLE ISLAND. ANIMATED
RADAR IMAGERY REVEALS A PARTIAL EYEWALL WITH EXTENSIVE SPIRAL BANDING, 
WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. SURFACE 
OBSERVATIONS FROM DARWIN INDICATE 25-30 KNOT SUSTAINED SOUTHEASTERLIES 
(10-MINUTE AVERAGE) OVER THE PAST SIX HOURS WITH MINIMUM SLP NEAR 
996.2MB. SURFACE OBSERVATIONS TO THE WEST FROM POINT FAWCETT, 57NM 
WEST, ARE SIGNIFICANTLY LOWER AT 15-17 KNOTS SUSTAINED. 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. TC 05S HAD INTENSIFIED UNTIL 220600Z 
WHEN IT TRACKED OVER THE SOUTHERN TIP OF MELVILLE ISLAND BUT HAS SINCE 
WEAKENED SLIGHTLY. SUBJECTIVE DVORAK ESTIMATES JUMPED TO T5.5 (102 
KNOTS), WITH CIMSS OBJECTIVE ESTIMATES VARYING FROM 78-93 KNOTS. THE 
INITIAL INTENSITY IS ASSESSED AT 90 KNOTS WITH MEDIUM CONFIDENCE BASED 
ON AN AVERAGE OF THE SUBJECTIVE AND OBJECTIVE ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   ADRM: T5.5 - 102 KTS
   CIMSS ADT: 82 KTS AT 220600Z
   CIMSS AIDT: 78 KTS AT 220600Z
   CIMSS D-MINT: 84 KTS AT 220600Z
   CIMSS D-PRINT: 93 KTS AT 220536Z

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 48 OVER THE JOSEPH
BONAPARTE GULF. AFTER TRACKING AWAY FROM MELVILLE ISLAND, TC FINA
IS FORECAST TO INTENSIFY THROUGH TAU 12 UNDER FAVORABLE CONDITIONS
TO A PEAK INTENSITY OF 100 KNOTS. INCREASING DRY AIR ENTRAINMENT
AND HIGH (25 KNOTS) VWS WILL BEGIN TO WEAKEN THE SYSTEM NEAR TAU
24, WITH STEADY WEAKENING THROUGH TAU 48. AFTER TAU 48, 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 BETWEEN TAU 96 TO TAU 120.         

MODEL DISCUSSION: DETERMINISTIC GUIDANCE IS IN GOOD AGREEMENT THROUGH 
ONLY TAU 24, WITH A LARGE SPREAD AND INCREASING UNCERTAINTY AFTER TAU 
72. THE 220000Z GEFS AND EPS RUNS ALSO INDICATE LARGE SPREAD AND HIGH 
UNCERTAINTY. THERE IS ALSO A LARGE SPREAD IN INTENSITY GUIDANCE, WITH 
HAFS-A INDICATING A MOIST CORE COCOONED FROM THE DRY AIR AND RAPID 
INTENSIFICATION FROM TAU 12 TO TAU 36 (PEAK INTENSITY OF 118 KNOTS 
OCCURS AT TAU 48). THE 220000Z GFS RAW OUTPUT, WHICH INDICATES AN 
INITIAL INTENSITY OF 66 KNOTS, RAPIDLY WEAKENS THE SYSTEM THROUGH TAU 
12. THE 220000Z COAMPS-TC (GFS) SHOWS AN INITIAL INTENSITY OF 78 KNOTS 
BUT ALSO RAPIDLY WEAKENS THE SYSTEM THROUGH TAU 36.     

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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