WDXS31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (FIVE)        
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.0S 130.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 150 NM NORTH OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 05S HAS CONSOLIDATED SUFFICIENTLY OVER THE PAST 
SIX HOURS TO WARRANT ISSUANCE OF THE FIRST WARNING. ANIMATED 
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS IMPROVED CONVECTIVE
BANDING WRAPPING AROUND A PARTIALLY-EXPOSED, WELL-DEFINED LOW-LEVEL
CIRCULATION CENTER (LLCC), WITH VIGOROUS LOW-LEVEL CLOUD LINES WRAPPING 
INTO THE SYSTEM. ANIMATED RADAR IMAGERY FROM THE DARWIN RADAR REVEALS A 
PERSISTENT CURVED CONVECTIVE BAND OVER THE SOUTHERN SEMICIRCLE, JUST 
NORTH OF MELVILLE ISLAND, WITH WEAKER BANDING WRAPPING INTO THE 
NORTHWEST QUADRANT OF A DEFINED LLCC. AN 180450Z AMSR2 36GHZ MICROWAVE 
IMAGE SHOWS LOW-LEVEL BANDING WRAPPING TIGHTLY INTO A WELL-DEFINED 
LLCC, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. 
RELEVANT SURFACE OBSERVATIONS ARE SPARSE WITH THE EXCEPTION OF POINT 
FAWCETT ON THE WESTERN COAST OF MELVILLE ISLAND, WHICH IS REPORTING 
ONLY 5-10 KNOT EASTERLY SUSTAINED WINDS. HOWEVER, AN 180018Z ASCAT-C 
IMAGE INDICATES PATCHY 35 KNOT WINDS WITHIN ABOUT 20NM OF THE CENTER. 
AGENCY DVORAK FINAL-T INTENSITY ESTIMATES RANGE FROM T2.0-2.5 (30-35 
KNOTS), WHICH ALSO SUPPORTS THE INITIAL INTENSITY WITH HIGH CONFIDENCE. 
THE INITIAL WIND RADII ARE BASED ON THE ASCAT-C DATA. ENVIRONMENTAL
CONDITIONS ARE CURRENTLY FAVORABLE WITH RADIAL OUTFLOW, WARM SST
VALUES AND LOW VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL NEAR-EQUATORIAL RIDGE
(NER) POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   ADRM: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 05S WILL TRACK SLOWLY EASTWARD OVER THE NEXT 
TWO DAYS ALONG THE SOUTHERN PERIPHERY OF THE NER. THE SYSTEM IS 
FORECAST TO PEAK TO ABOUT 55 KNOTS DURING THIS TIMEFRAME, WITH 
GENERALLY FAVORABLE CONDITIONS PERSISTING THROUGH ABOUT TAU 36. NEAR 
TAU 36, VERTICAL WIND SHEAR (VWS) IS FORECAST TO INCREASE TO HIGH (25-
30 KNOTS) LEVELS, WHICH WILL TILT THE VORTEX SOUTHWESTWARD, WITH DRY 
AIR ENTRAINING INTO THE EASTERN QUADRANT OF THE CORE. THIS WILL 
INITIATE A GRADUAL WEAKENING TREND THROUGH TAU 48. AFTER TAU 48, THE 
SUBTROPICAL RIDGE TO THE SOUTH AND EAST IS EXPECTED TO BROADEN AND 
STRENGTHEN BECOMING THE DOMINANT STEERING INFLUENCE THROUGH THE 
REMAINDER OF THE FORECAST. THIS WILL DRIVE THE SYSTEM INITIALLY 
SOUTHWARD THROUGH TAU 72 THEN WEST-SOUTHWESTWARD TO WESTWARD THROUGH 
TAU 120. AFTER TAU 72, INTERACTION WITH THE NORTHERN COAST OF AUSTRALIA 
WILL LEAD TO FURTHER WEAKENING AS THE SYSTEM SKIRTS THE COASTAL REGION. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT LENDING 
MEDIUM CONFIDENCE TO THE JTWC TRACK FORECAST, WITH SIGNIFICANT 
UNCERTAINTY IN THE TIMING OF THE SHARP SOUTHWARD AND WESTWARD TURNS. 
THE 180000Z GEFS AND EPS RUNS ALSO REFLECT SIMILAR UNCERTAINTY. DUE TO 
THE TRACK UNCERTAINTY AND PROXIMITY TO LAND, THERE IS MEDIUM CONFIDENCE 
IN THE JTWC INTENSITY FORECAST, WITH RELIABLE GUIDANCE INDICATING A 
FAIRLY WIDE SPREAD OF PEAK INTENSITY VALUES RANGING FROM 45 TO 65 KNOTS 
IN THE TAU 24 TO TAU 36 PERIOD. 

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