WDXS31 PGTW 170300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (ERROL) WARNING NR 022// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.0S 119.0E INITIAL INTENSITY: 120 KTS GEOGRAPHIC REFERENCE: 253 NM NORTHWEST OF BROOME, AUSTRALIA MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 04 KTS SIGNIFICANT WAVE HEIGHT: 32 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL CYCLONE (TC) 29S (ERROL) EXPERIENCING A RAPID DECLINE IN CONVECTIVE ORGANIZATION AS IT TRACKS TOWARD THE WEST KIMBERLEY COAST. INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE NEARLY COMPLETELY FILLED EYE FEATURE PRESENT IN THE VISIBLE IMAGERY LOOP. ANALYSIS REVEALS AN INCREASING AMOUNT OF DRY AIR WRAPPING INTO THE SYSTEM, AS WELL AS SIGNIFICANTLY LESS UNIFORM CENTRAL DENSE OVERCAST (CDO) AND MORE PRONOUNCED SPIRAL BANDS OF DEEP CONVECTION. POLEWARD OUTFLOW REMAINS STRONG AND AS THE SYSTEM SPEEDS UP, IT CAN YET AGAIN TAP INTO THE WARM (29-30 C) WATERS OF THE INDIAN OCEAN. HOWEVER, ANY POTENTIAL REDEVELOPMENT WILL BE HALTED BY STRONG (20-25 KTS) AND INCREASING WESTERLY VERTICAL WIND SHEAR (VWS) AND LOW MOISTURE CONTENT AVAILABLE THROUGHOUT THE COLUMN. CURRENT INTENSITY IS ESTIMATED AT 120 KTS, WITH MEDIUM CONFIDENCE, BASED ON DVORAK SATELLITE ANALYSIS AND SUPPORTING OBJECTIVE ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: WEAK STEERING BY A SUBTROPICAL RIDGE (STR) TO THE EAST AND INFLUENCE FROM A PASSING LONG WAVE TROUGH TO THE SOUTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T7.0 - 140 KTS CIMSS ADT: 112 KTS AT 170010Z CIMSS AIDT: 110 KTS AT 170010Z CIMSS D-MINT: 117 KTS AT 162220Z CIMSS D-PRINT: 118 KTS AT 170010Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 20-25 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG POLEWARD 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 29S IS EXPECTED TO CONTINUE MOVING SOUTHEASTWARD, GUIDED BY A WEAKENING SUBTROPICAL RIDGE (STR) TO THE EAST, WHICH ITSELF IS GRADUALLY SHIFTING EQUATORWARD. MEANWHILE, AN UPPER-LEVEL TROUGH TO THE SOUTH OF TC ERROL IS ADVANCING EASTWARD. AHEAD OF THIS TROUGH, STRONG WESTERLY WINDS ARE AFFECTING THE CYCLONE, BRINGING IN HIGH VERTICAL WIND SHEAR, WHICH WILL LEAD TO A DECAPITATION OF THE DEEP CONVECTION WITHIN THE NEXT 24 HOURS. AS A RESULT, TC 29S IS FORECAST TO CONTINUE TO RAPIDLY WEAKEN, WHILE TRACKING TOWARD AUSTRALIA. THE CYCLONE IS EXPECTED TO MAKE LANDFALL OVER THE NORTHERN DAMPIER PENINSULA BETWEEN TAUS 36 AND 48. INTENSITY AT THE TIME OF LANDFALL IS FORECAST TO DROP TO 45 KTS, AND THE SYSTEM IS EXPECTED TO COMPLETELY DISSIPATE OVER LAND, BY THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS COMING TO A BETTER AGREEMENT THAN DURING THE PREVIOUS FORECAST, AS WITNESSED BY A 50 NM CROSS TRACK SPREAD AT THE TIME OF LANDFALL, WITH THE EXCLUSION OF GALWEM, WHICH STILL SUGGEST A TRACK TO THE NORTH OF THE CONSENSUS, WITH LANDFALL NEAR WALCOTT INLET. ALONG-TRACK SPREAD IS NOT AS GOOD HOWEVER, WITH 135 NM ACROSS THE GUIDANCE AT TAU 36. JTWC TRACK IS THEREFORE LAID WITH MEDIUM CONFIDENCE AND CLOSE TO THE MULTI-MODEL CONSENSUS. IN TERMS OF INTENSITY, MODELS ARE IN GOOD AGREEMENT THAT TC ERROL WILL CONTINUE TO WEAKEN RAPIDLY. GFS AND COAMPS-TC ARE NOW THE MOST AGGRESSIVE, PREDICTING DISSIPATION BEFORE 36 HOURS. THE DECAY SHIPS MODEL IS MORE CONSERVATIVE, BUT STILL FORECASTS COMPLETE DISSIPATION BEFORE 72 HOURS. HAFS IS NOW ALSO LESS AGGRESSIVE AND MAINTAINS WINDS ABOVE 35 KTS UNTIL AT LEAST TAU 48. AS A RESULT, THE JTWC INTENSITY FORECAST IS LAID WITH MEDIUM CONFIDENCE, CLOSELY FOLLOWING THE MULTI-MODEL CONSENSUS THROUGHOUT THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN