WDXS31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY)     
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.3S 113.7E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 410 NM NORTHWEST OF PORT HEDLAND,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS WEAK
SPIRAL BANDING OVER THE WESTERN SEMICIRCLE WITH A FAIRLY SYMMETRIC
CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW-LEVEL CIRCULATION
CENTER (LLCC). EIR INDICATES PERSISTENT EASTERLY VERTICAL WIND
SHEAR (VWS), WHICH CONTINUES TO HINDER THE DEVELOPMENT OF AN EYE
DESPITE SEVERAL FEEBLE ATTEMPTS. A 080546Z ATMS 88.2GHZ MICROWAVE
IMAGE REVEALS A PARTIAL EYEWALL OVER THE WESTERN QUADRANT WITH THE 
BULK OF THE DEEP CONVECTION DISPLACED OVER THE WESTERN SEMICIRCLE DUE 
TO THE AFOREMENTIONED MODERATE TO HIGH EASTERLY VWS. THE INITIAL 
POSITION IS PLACED ALONG THE EASTERN EDGE OF THE PARTIAL EYEWALL IN 
THE ATMS IMAGE WITH HIGH CONFIDENCE. OVERALL, ENVIRONMENTAL CONDITIONS 
REMAIN FAVORABLE WITH MODERATE EQUATORWARD AND POLEWARD OUTFLOW AND 
WARM SST OFFSETTING THE VWS SOMEWHAT. THE INITIAL INTENSITY OF 95 KTS 
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW, APRF AND KNES 
DVORAK ESTIMATES. THIS IS SLIGHTLY HIGHER THAN THE ADT AND AIDT 
ESTIMATES OF 87 AND 83 KNOTS, RESPECTIVELY, BUT IN LINE WITH THE MOST 
RECENT OPEN-AIIR ESTIMATE OF 94 KNOTS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTH OVER WESTERN AUSTRALIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   APRF: T5.0 - 90 KTS
   CIMSS SATCON: 74 KTS AT 080544Z
   CIMSS ADT: 87 KTS AT 080530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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: TC 11S IS FORECAST TO TRACK WESTWARD ALONG THE
NORTHERN PERIPHERY OF THE STR THROUGH THE FORECAST PERIOD. MODERATE
TO HIGH VWS IS EXPECTED TO PERSIST THROUGH TAU 36, WHICH SHOULD
LEAD TO A STEADY WEAKENING TREND. AFTER TAU 36, VWS IS FORECAST TO
RELAX ALLOWING FOR A REINTENSIFICATION PHASE. 

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH REMAINS
SIGNIFICANTLY LEFT OF TRACK, THE BULK OF THE DETERMINISTIC GUIDANCE
REMAINS IN GOOD AGREEMENT WITH A 55 TO 90NM SPREAD IN SOLUTIONS
FROM TAU 72 TO TAU 120. THE 071800Z ECMWF ENSEMBLE (EPS) IS IN
BETTER AGREEMENT WITH THE BULK OF SOLUTIONS SHOWING A WESTWARD
TRACK. AFTER TAU 72, EPS INDICATES INCREASING SPREAD IN THE TAU 96
AND TAU 120 FORECAST POSITIONS REFLECTING INCREASING UNCERTAINTY IN
THE JTWC FORECAST TRACK. THERE IS SIGNIFICANT UNCERTAINTY IN THE
JTWC INTENSITY FORECAST WITH RELIABLE INTENSITY GUIDANCE REVEALING
A LARGE SPREAD AFTER TAU 24. HWRF INDICATES A SHARP WEAKENING TREND
TO ABOUT 50 KNOTS THEN A SHARP REINTENSIFICATION TO 90 KNOTS BY TAU
96. COAMPS-TC (GFS VERSION) CONTINUES TO INDICATE RAPID 
INTENSIFICATION (RI) TO 135 KNOTS BY TAU 84, WHICH IS WELL ABOVE
THE OTHER GUIDANCE. PROBABILITY VALUES ASSOCIATED WITH THIS RI
PHASE ARE 30 TO 40 PERCENT FROM TAU 36 TO TAU 66.       

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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