WDXS31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 17S (LUANA) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.6S 122.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 78 NM NORTH OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 17S (LUANA) CONTINUES TO INTENSIFY AS IT
TRACKS TOWARDS LANDFALL ON THE DAMPIER PENINSULA. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A WELL-DEFINED, THOUGH 
PARTIALLY OBSCURED, LOW LEVEL CIRCULATION CENTER (LLCC) WITH SPIRAL
RAIN BANDS WRAPPING INTO THE ASSESSED CENTER. ANIMATED RADAR IMAGERY 
FROM ABOM INDICATES THE LLCC REMAINS SOMEWHAT BROAD; HOWEVER, 
CONSOLIDATION OF THE INNER CORE STRUCTURE HAS ACCELERATED OVER THE 
PAST FEW HOURS. A 232115Z WSF-M COLOR-ENHANCED 37GHZ MICROWAVE IMAGE 
REVEALED AN IRREGULAR SHAPED MICROWAVE EYE FEATURE, WITH A BREAK IN 
THE EYEWALL ON THE EASTERN, UP SHEAR SIDE. THE INITIAL POSITION IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE RADAR DATA AND 
EXTRAPOLATION OF THE MICROWAVE EYE. THE INITIAL INTENSITY IS ASSESSED 
WITH MEDIUM CONFIDENCE BASED ON THE SUBJECTIVE AND OBJECTIVE ESTIMATES 
NOTED BELOW. THE ENVIRONMENT REMAINS CONDUCIVE TO DEVELOPMENT, THOUGH 
HINDERED BY THE PROXIMITY TO LAND AND THE VERY SHORT TIME REMAINING 
OVER WATER.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
NEAR EQUATORIAL RIDGE (NER) CENTERED FAR TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   ADRM: T3.0 - 45 KTS
   APRF: T3.0 - 45 KTS
   CIMSS ADT: 51 KTS AT 240000Z
   CIMSS AIDT: 44 KTS AT 240000Z
   CIMSS D-MINT: 44 KTS AT 232118Z
   CIMSS D-PRINT: 45 KTS AT 240020Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: PROXIMITY TO 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: TROPICAL CYCLONE (TC) 17S WILL CONTINUE TO
TRACK SOUTHEASTWARD OVER THE NEXT 24 HOURS ALONG THE SOUTHWESTERN
PERIPHERY OF THE NER TO THE NORTH. AFTER TAU 24, A BUILDING RIDGE
OVER CENTRAL AUSTRALIA WILL TAKE OVER AS THE DOMINATE STEERING
MECHANISM, TURNING TC 17S ON A SOUTHWARD TRAJECTORY TOWARDS THE
GREAT SANDY DESERT. THE CENTER OF TC 17S IS EXPECTED TO MAKE
LANDFALL WITHIN THE NEXT COUPLE OF HOURS, ALONG THE COAST OF THE
DAMPIER PENINSULA. AFTER LANDFALL, THE CENTER WILL PASS CLOSE TO OR
POSSIBLY OVER THE SOUTHERN PORTION OF KING SOUND, BEFORE TURNING
SOUTHWARD TO THE EAST OF BROOME. REGARDING INTENSITY, A MARGINAL 
INCREASE MAY OCCUR PRIOR TO LANDFALL, THOUGH THE SYSTEM IS LIKELY 
APPROACHING PEAK OPERATIONAL INTENSITY. THE SYSTEM WILL GRADUALLY 
DECAY AFTER LANDFALL, THOUGH THE RATE OF WEAKENING COULD SLOW SHOULD 
THE CORE TRACK OVER THE THERMALLY CONDUCTIVE WATERS OF KING SOUND. 
ACCELERATED WEAKENING IS EXPECTED AFTER TAU 12 AS THE SYSTEM PROCEEDS 
FURTHER INLAND. THE SYSTEM WILL DISSIPATE AS A SIGNIFICANT TROPICAL 
CYCLONE BY TAU 36, ALTHOUGH THE RESIDUAL CYCLONIC VORTEX IS LIKELY TO 
PERSIST AS IT TRAVERSES THE GREAT SANDY DESERT. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT ON
THE FORECAST TRACK, WITH LITTLE IN THE WAY OF EITHER CROSS- OR
ALONG-TRACK UNCERTAINTY. THE JTWC FORECAST IS PLACED NEAR THE
MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS
ALSO IN GOOD AGREEMENT, SHOWING THE SYSTEM STEADILY WEAKENING TO 30
KNOTS WITHIN THE NEXT 36 HOURS, THEN LINGERING BETWEEN 25-30 KNOTS
FOR THE NEXT FIVE DAYS. THE JTWC FORECAST IS PLACED NEAR THE
CONSENSUS MEAN WITH HIGH CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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