WDXS31 PGTW 151500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (ERROL) WARNING NR 016// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.9S 120.8E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 253 NM NORTH-NORTHWEST OF BROOME, AUSTRALIA MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN EXTREMELY SMALL AND COMPACT TROPICAL CYCLONE (TC), WITH TWO SEPARATED AREAS OF DEEP CONVECTION. ONE AREA OF CONVECTION HAS SLID WESTWARD TO THE SOUTH OF THE ASSESSED CENTER, WHILE THE OTHER AREA HAS SPLIT OFF AND COCOONED ITSELF INTO A TINY BUBBLE NEAR THE LLCC. THE MOST RECENT FRAMES OF EIR SUGGEST THESE TWO AREAS MAY BE STARTING TO ROTATE AROUND ONE ANOTHER BUT ITS YET TOO EARLY TO TELL FOR CERTAIN. A 151028Z WSF-M COLOR ENHANCED 37GHZ MICROWAVE IMAGE REVEALED A SMALL BUT WELL-DEFINED LLCC WITH DEVELOPING BANDING FEATURES SURROUNDING THE CENTER. COMPARISON TO THE 89GHZ CHANNEL REVEALED A NEARLY VERTICALLY ALIGNED VORTEX, AND A WEAK BUT DEVELOPING MICROWAVE EYE-LIKE FEATURE IN THE UPPER-LEVELS. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE TIGHT GROUPING OF AGENCY FIX POSITIONS AND EXTRAPOLATION OF THE MICROWAVE DATA DISCUSSED ABOVE. THE INITIAL INTENSITY IS INCREASED TO 55 KNOTS WITH MEDIUM CONFIDENCE, HEDGED TOWARDS THE T3.5 FIX INTENSITIES FROM BOTH PGTW AND KNES. THE OBJECTIVE ESTIMATES LIKELY CONTINUE TO BE TOO LOW DUE TO THE COMPACT NATURE OF THE CORE OF THE SYSTEM. THE ENVIRONMENT REMAINS VERY FAVORABLE FOR POSSIBLE RAPID INTENSIFICATION (RI), WITH LOW WIND SHEAR, ZESTY SSTS AND GOOD RADIAL OUTFLOW WITH ENHANCED POLEWARD OUTFLOW AHEAD OF A SHORTWAVE TROUGH EAST OF PORT HEDLAND. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF AN EXTENSION OF THE SUBTROPICAL RIDGE (STR) TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS KNES: T3.5 - 55 KTS APRF: T3.0 - 45 KTS CIMSS SATCON: 38 KTS AT 151130Z CIMSS ADT: 43 KTS AT 151130Z CIMSS AIDT: 36 KTS AT 151130Z CIMSS D-MINT: 39 KTS AT 151053Z CIMSS D-PRINT: 43 KTS AT 151130Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM 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 (ERROL) IS FORECAST TO CONTINUE TRACKING GENERALLY WESTWARD ALONG THE NORTHERN SIDE OF THE EXTENSION OF THE STR FOR THE NEXT 12 TO 24 HOURS. A SLIGHT TURN TOWARDS THE SOUTHWEST IS ANTICIPATED TO START AROUND TAU 24, WITH THE TURN SHARPENING AFTER TAU 24 AS THE SYSTEM DIVES SOUTHWARD INTO A BREAK IN THE RIDGE CAUSED BY THE APPROACH OF A DEEP TROUGH. IN THE SHORT-TERM, TC ERROL IS EXPECTED TO INTENSIFY RELATIVELY QUICKLY OVER THE NEXT 12 HOURS NOW THAT THE VORTEX APPEARS TO HAVE BECOME VERTICALLY ALIGNED. RI COMMENCES AROUND TAU 12, WITH AN EXPECTED 30 KNOT INTENSIFICATION THROUGH TAU 36, REACHING A PEAK OF AT LEAST 100 KNOTS BY THAT POINT. A DRAMATIC INCREASE IN NORTHWESTERLY SHEAR IS EXPECTED TO MAKE ITSELF KNOWN IMMEDIATELY AFTER TAU 36, WITH SHEAR FORECAST TO INCREASE UP FROM ABOUT 15 KNOTS TO OVER 30 KNOTS IN A VERY SHORT PERIOD OF TIME, WHICH WILL QUICKLY DECAPITATE THE SYSTEM. RAPID WEAKENING WILL COMMENCE JUST AFTER THE SYSTEM PEAKS, WITH INTENSITY EXPECTED TO DROP TO 70 KNOTS BY TAU 48. AS THE SYSTEM IS SHEARED APART, DRY MID-LEVEL AIR WILL ALSO MOVE IN AND SMOTHER THE REMAINING VORTEX, WHICH WILL SIMULTANEOUSLY BE SHALLOWING AT A RAPID PACE DURING THIS TIMEFRAME. PICKED UP BY THE DEEP TROUGH MOVING IN FROM THE WEST, THE REMNANT VORTEX WILL TURN SHARPLY SOUTHEAST AND TRACK TOWARDS THE NORTHWESTERN COAST OF AUSTRALIA THROUGH THE REMAINDER OF THE FORECAST. THE FORECAST CALLS FOR THE WEAKENING VORTEX TO MAKE LANDFALL NORTHEAST OF BROOME, BUT SEVERAL MODELS SUGGEST THE SYSTEM MAY WEAKEN AND DISSIPATE PRIOR TO REACHING THE COAST AND-OR TURNING BACK TO THE SOUTHWEST UNDER THE INFLUENCE OF THE LOW-LEVEL FLOW PATTERN PRIOR TO REACHING THE COAST. BOTH SCENARIOS REMAIN IN PLAY AND THERE IS A HIGH DEGREE OF UNCERTAINTY IN THE EXTENDED FORECAST. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE AGREEMENT HAS IMPROVED OVER THE PAST SIX HOURS, WITH THE BULK OF THE CONSENSUS MEMBERS NOW IN FAIRLY GOOD CROSS- AND ALONG-TRACK AGREEMENT THROUGH TAU 48. THE GEFS MEAN STILL PUSHES THE LLCC FURTHER WEST THAN THE OTHER MEMBERS OF THE CONSENSUS BEFORE TURNING SOUTHEAST, AND THE NAVGEM IS DISCOUNTED DUE TO A STRAIGHT SOUTHWEST TRACK FROM TAU 00. THE REMAINDER OF THE CONSENSUS MEMBERS ARE CONFINED TO A 70NM ENVELOPE AT TAU 48. THE GUIDANCE QUICKLY DIVERGES AFTER TAU 48 HOWEVER AS THE SYSTEM WEAKENS, WITH CROSS-TRACK SPREAD BETWEEN THE GEFS AND THE GALWEM OPENING UP TO 350NM BY TAU 72, THOUGH ALL MODELS SHOW THE SYSTEM TRACKING TOWARDS THE SOUTHEAST AT THIS POINT. WITH THE EXCEPTION OF THE ECMWF AND EGRR, THE BULK OF THE GUIDANCE SHOWS THE SYSTEM TURNING SOUTHWESTWARD AROUND TAU 96, THOUGH THE MODELS VARY SIGNIFICANTLY ON THE STARTING POINT OF THE TURN, SOME OFFSHORE, SOME ONSHORE, SUCH THAT SPREAD INCREASES EVEN FURTHER BY THE END OF THE FORECAST. WITH SUCH HIGH DEGREES OF UNCERTAINTY, THE JTWC FORECAST IS PLACED NEAR THE CONSENSUS MEAN WITH LOW CONFIDENCE. INTENSITY GUIDANCE REMAINS IN FAIRLY GOOD AGREEMENT, THOUGH THE PEAK INTENSITIES HAVE COME DOWN QUITE A BIT. MULTIPLE RI AIDS ARE STILL TRIPPED, BUT NO MODEL SHOWS A PEAK INTENSITY ABOVE 100 KNOTS, WITH THE HWRF DOWN TO 95 KNOTS, WHILE THE HAFS-A HAS GONE FROM 115 KNOTS TO JUST 70 KNOTS. ALL MODELS EXCEPT COAMPS-TC REACH PEAK INTENSITY BETWEEN TAU 24 AND TAU 36 BEFORE A RAPID DROP OFF. THE JTWC FORECAST IS PLACED AMONGST THE RI GUIDANCE TRENDS, ABOVE THE OTHER GUIDANCE WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN