WDXS31 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 17S (SEVENTEEN) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.3S 119.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 309 NM NORTH-NORTHWEST OF BROOME,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
OVER THE PAST 6 HOURS TROPICAL CYCLONE (TC) 17S HAS CONSOLIDATED
RAPIDLY AS DEPICTED BY ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI). DEEP CONVECTION HAS BUILT ESPECIALLY IN THE NORTHWEST
QUADRANT OF THE CIRCULATION AS DEPICTED BY ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON ANIMATED MSI IMAGERY OF THE PARTIALLY
OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC) CONSISTENT WITH THE
220050Z PARTIAL ASCAT PASS. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE PREVIOUSLY MENTIONED
220050Z ASCAT DATA AND PGTW AGENCY FIX.

INITIAL WIND RADII BASIS: OTHER 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE CENTERED TO THE
NORTH 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   APRF: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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 17S WILL CONTINUE TRACKING TO THE SOUTHEAST
UNDER THE INFLUENCE OF THE NEAR EQUATORIAL RIDGE TO THE NORTH. THE
FORECASTED ENVIRONMENT WILL REMAIN FAVORABLE FOR CONTINUED
DEVELOPMENT OF THE SYSTEM WITH WARM SEA SURFACE TEMPERATURES (29C
TO 30C), LOW VERTICAL WIND SHEAR (10-15 KTS), AND IMPROVING
OUTFLOW, THOUGH THE SYSTEM DOES NOT HAVE LONG BEFORE IT TRACKS
INLAND OF THE NORTHWESTERN COAST OF AUSTRALIA. THIS IS EXPECTED TO
LIMIT THE CIRCULATION TO A MAXIMUM INTENSITY OF AROUND 50 KTS.
INTENSIFYING HIGHER THAN 50 KTS IS NOT OUT OF THE QUESTION AS THE
STORM HAS ALREADY UNDERGONE A PERIOD OF RAPID IMPROVEMENT WITH A
SIMILAR SET OF ENVIRONMENTAL CONDITIONS. AFTER TRACKING INLAND
BETWEEN TAU 24 AND 36, THE SYSTEM WILL RAPIDLY WEAKEN AND DISSIPATE
OVER LAND BY TAU 48.   

MODEL DISCUSSION: CROSS TRACK SPREAD AMONGST MODEL GUIDANCE IS
UNDER 70 NM FOR THE MAJORITY OF THE FORECAST PERIOD. GFS IS LEADING
THE NORTHERNMOST TRACKS WHILE AIFS IS REPRESENTING THE SOUTHERNMOST
TRACK. WHILE GFS MOST ACCURATELY DEPICTS THE STRUCTURE OF THE STORM
AT THE MOMENT, A MAJORITY OF THE MODELS LEAN TOWARDS THE AIFS
DEPICTION. AS SUCH, THE JTWC TRACK FORECAST IS PLACED JUST SOUTH OF
THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE IS IN GOOD AGREEMENT WITH A SPREAD OF 10-15 KTS EXCLUDING
ONE RAPID INTENSIFICATION MODEL. THE JTWC INTENSITY FORECAST
REFLECTS VALUES IN LINE WITH THE MULTI MODEL CONSENSUS WITH MEDIUM
CONFIDENCE.

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