WDPS31 PGTW 180300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 12.4S 153.3E INITIAL INTENSITY: 65 KTS GEOGRAPHIC REFERENCE: 512 NM EAST-NORTHEAST OF CAIRNS, AUSTRALIA MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 25 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT INNER-CORE OF RAPIDLY DEVELOPING DEEP CONVECTION, AND EVIDENCE OF A NASCENT EYE FEATURE, ACCOMPANIED BY A CORRESPONDING WARM SPOT IN THE ENHANCED INFRARED (EIR) IMAGERY. A RECENT DROUGHT IN MICROWAVE IMAGERY PRECLUDES AN ACCURATE ASSESSMENT OF THE VERTICAL WARM CORE STRUCTURE; THEREFORE, THE DEGREE OF VERTICAL VORTEX TILT IS CURRENTLY INDETERMINATE. THE SYSTEM EARLIER EXHIBITED A CENTRAL COLD COVER (CCC) STRUCTURE, CHARACTERISTIC OF ARRESTED DEVELOPMENT, DURING WHICH OBJECTIVE INTENSITY ESTIMATES REMAINED STAGNANT FOR APPROXIMATELY 12 HOURS. HOWEVER, IN THE PAST SIX HOURS, THE LOW-LEVEL CIRCULATION CENTER (LLCC) IS ASSESSED TO HAVE BECOME INCREASINGLY AXISYMMETRIC AS CONVECTION HAS BEGUN TO WRAP UPSHEAR, INDICATING THE ONSET OF INTENSIFICATION. THE MOST RECENT MICROWAVE DATA ACQUIRED WAS A 171744Z SSMIS PASS WHICH REVEALED A 37GHZ EYE FEATURE WITH A CYAN RING, INDICATIVE OF POTENTIAL RAPID INTENSIFICATION IN THE NEAR-TERM. A 172254Z ASCAT-C PASS REVEALED A VERY COMPACT INNER-CORE, WITH THE ULTRA-HIGH RESOLUTION (UHR) VERSION INDICATING MAXIMUM WINDS OF 66 KNOTS. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON AN EXTRAPOLATION OF THE ASCAT-DERIVED CENTER. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW, CONFIRMED BY THE ASCAT PASS. ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE OF RAPID INTENSIFICATION (RI), WITH LOW VWS, VERY WARM SSTS, MODERATE OHC AND STRONG OUTFLOW ALOFT. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) OVER NORTHEASTERN AUSTRALIA. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.0 - 65 KTS KNES: T4.0 - 65 KTS ABRF: T4.0 - 65 KTS CIMSS ADT: 59 KTS AT 180000Z CIMSS AIDT: 65 KTS AT 180000Z CIMSS D-PRINT: 66 KTS AT 180030Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG WESTWARD OTHER FACTORS: MODERATE EQUATORWARD OUTFLOW. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 27P (NARELLE) REACHED ITS MOST EQUATORWARD LATITUDE AT 1800Z AND IS NOW TRACKING GENERALLY WESTWARD ALONG THE NORTHERN PERIPHERY OF THE STR ANCHORED OVER NORTHEASTERN AUSTRALIA. THE RIDGE IS FORECAST TO BUILD AND EXTEND NORTHEASTWARD OVER THE NEXT 24 HOURS, PLACING TC 27P ON THE NORTHWESTERN PERIPHERY, RESULTING IN A WEST-SOUTHWESTWARD TRACK TAU 24. BY TAU 36, THE TRACK FLATTENS TO A DUE WESTWARD TRAJECTORY WHILE SIMULTANEOUSLY DECELERATING AS A WEAKNESS DEVELOPS IN THE RIDGE IN RESPONSE TO PASSAGE OF A SHORTWAVE TROUGH TO THE SOUTH. LANDFALL JUST NORTH OF PRINCESS CHARLOTTE BAY IS EXPECTED JUST AFTER TAU 48. THE SYSTEM CROSSES THE CAPE YORK PENINSULA BY TAU 60 AND EMERGES INTO THE GULF OF CARPENTARIA. TC 27P THEN ACCELERATES SLIGHTLY AS THE STEERING RIDGE ENTRENCHES OVER CENTRAL AUSTRALIA. A SECOND LANDFALL IS EXPECTED ALONG THE WESTERN COAST OF THE GULF AROUND TAU 84, WITH THE SYSTEM CONTINUING INLAND TO THE SOUTH OF DARWIN AND MOVING OVER THE NORTHWEST COAST BY TAU 120. IN TERMS OF INTENSITY, THE SYSTEM IS PRIMED TO INITIATE RI IMMINENTLY. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN OPTIMAL THROUGH AT LEAST TAU 36, SUPPORTING RI UP TO A PEAK INTENSITY OF AT LEAST 115 KNOTS. AS THE SYSTEM PASSES NORTH OF CAPE MELVILLE, THE INNER CORE WILL BE STRUCTURALLY DEGRADED AS PERIPHERAL INFLOW BANDS INTERACT WITH THE OROGRAPHY IN AND AROUND CAPE MELVILLE. SIMULTANEOUSLY, EASTERLY SHEAR WILL BEGIN TO INCREASE TO MODERATE LEVELS. FRICTIONAL EFFECTS AUGMENTED BY SHEAR WILL RESULT IN VERTICAL VORTEX DISPLACEMENT BY THE TIME IT CROSSES THE CAPE YORK PENINSULA, LEADING TO A RAPID WEAKENING PHASE, THOUGH THE SYSTEM IS STILL EXPECTED TO MOVE INTO THE GULF OF CARPENTARIA AS A STRONG TROPICAL STORM. THE DISCRETE FORECAST POINTS DEPICT A SLOWLY WEAKENING STORM BETWEEN TAU 72 AND TAU 96, THOUGH IN REALITY THE SYSTEM IS FORECAST TO INTENSIFY TO A PEAK OF 70 KNOTS AT TAU 84, THEN WEAKEN ONCE AGAIN AFTER MAKING LANDFALL NEAR GROOTE EYLANDT. THE SYSTEM WILL CONTINUE TO WEAKEN THROUGH THE REMAINDER OF THE FORECAST PERIOD DUE TO LAND INTERACTION. MODEL DISCUSSION: THE CONSENSUS PACKAGE IS IN EXCELLENT AGREEMENT, WITH MINIMAL CROSS-TRACK SPREAD. THE NAVGEM HAS BEEN DISCOUNTED AS A STATISTICAL OUTLIER, TRACKING THE SYSTEM ERRONEOUSLY INTO THE RIDGE OVER CENTRAL AUSTRALIA. THE REMAINDER OF THE GUIDANCE IS CONFINED TO A 70NM ENVELOPE THROUGH TAU 120. ALONG-TRACK SPREAD IS SLIGHTLY HIGHER THAN THE CROSS-TRACK, HOWEVER IT CONTINUES TO CONVERGE WITH EACH MODEL RUN, NOW APPROXIMATELY 100NM BY TAU 120. THE JTWC FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS MEAN THROUGH THE FORECAST PERIOD WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD OVERALL AGREEMENT. ALL CONSENSUS MEMBERS AND NUMEROUS RI MODELS SUPPORT THE PEAK INTENSITY OCCURRING AT TAU 36, BETWEEN 100-130 KNOTS WITH STRONG AGREEMENT ON A 115 KNOT PEAK. THE POST-LANDFALL MINIMUM IS SHOWN TO OCCUR BETWEEN TAU 60 AND TAU 72, IN A RANGE BETWEEN 45-60 KNOTS, FOLLOWED BY A SECOND PEAK IN THE GULF OF CARPENTARIA BETWEEN TAU 84-96 AND A INTENSITY RANGE BETWEEN 50-80 KNOTS. THE JTWC FORECAST IS CONSISTENT WITH THE RI AIDS THROUGH TAU 36, THEN ROUGHLY CONSISTENT IN TREND TO THE CONSENSUS BUT PLACED ABOUT 10 KNOTS HIGHER THROUGH TAU 120. NEARLY ALL RI MODEL AIDS HAVE BEEN TRIGGED, ALONG WITH VERY HIGH (EXCEEDING 50 PERCENT) AI-RI PROBABILITIES, SUPPORT THE ONSET OF RI WITH HIGH CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 00-72 HR: HIGH INTENSITY 72-120 HR: MEDIUM// NNNN