WDPS31 PGTW 190300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.6S 147.8E INITIAL INTENSITY: 115 KTS GEOGRAPHIC REFERENCE: 229 NM NORTH-NORTHEAST OF CAIRNS, AUSTRALIA MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 34 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT AND RAPIDLY INTENSIFYING TROPICAL CYCLONE (TC) 27P (NARELLE). OVER THE LAST 12 HOURS, THE MAXIMUM INTENSITY INCREASED BY 25 KTS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A SMALL (10 NM IN DIAMETER) EYE FEATURE, PRESENT IN VISIBLE AND IR IMAGERY, SURROUNDED BY SYMMETRICAL, DEEP, AND DENSE CONVECTIVE CANOPY. CLOUD TOPS ARE ANALYZED AT -88 C, WHILE THE EYE TEMPERATURE HAS WARMED TO -46 C. THE INITIAL INTENSITY OF 115 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON AN EARLIER (181947Z) RCM-3 SAR PASS SHOWING EYEWALL WIND SPEEDS AT 110-115 KTS, SUPPORTED BY AGENCY DVORAK FIXES AND NEARLY ALL OBJECTIVE ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS CHARACTERIZED BY WARM (29-30 C) SEA SURFACE TEMPERATURES (SST), STRONG RADIAL OUTFLOW, MOIST ATMOSPHERIC COLUMN, OFFSET SLIGHTLY BY AN INCREASING EASTERLY VERTICAL WINDS SHEAR (VWS) REACHING 22-25 KTS, PARTICULARLY THROUGHOUT THE 400- 850 MB LEVELS. INITIAL WIND RADII BASIS: 181947Z RCM-3 SAR PASS CURRENT STEERING MECHANISM: NORTHEASTERN EXTENSION OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED OVER WESTERN AUSTRALIA AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.0 - 115 KTS KNES: T6.5 - 127 KTS ABRF: T6.5 - 127 KTS CIMSS SATCON: 122 KTS AT 182036Z CIMSS ADT: 112 KTS AT 190010Z CIMSS AIDT: 113 KTS AT 190010Z CIMSS D-MINT: 114 KTS AT 182036Z CIMSS D-PRINT: 110 KTS AT 190010Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 20-25 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC NARELLE IS FORECAST TO TRACK GENERALLY WESTWARD THROUGHOUT THE CURRENT FORECAST PERIOD, WITH ALL MODELS RECOGNIZING THE PRIMARY STEERING MECHANISM ASSOCIATED WITH A NORTHEASTERN EXTENSION OF A DEEP-LAYER STR CENTERED OVER WESTERN AUSTRALIA. WHILE THE RIDGE IS EXPECTED TO REPOSITION AND EXTEND ALONG THE NORTHWEST-SOUTHEAST AXIS AROUND TAU 96, TC 27P IS EXPECTED TO MAKE A SLIGHT WEST-SOUTHWESTWARD TURN, TRANSITING ALONG THE AUSTRALIAN COAST. BEYOND THE CURRENT FORECAST PERIOD, THE RIDGE IS PROJECTED TO STRENGTHEN, PUSHING TC NARELLE WESTWARD AND OVER OPEN WATER, BEFORE THE SYSTEM BEGINS TO ROUND THE WESTERN PERIPHERY OF THE STR. REGARDING THE SHORT TERM TRACK FORECAST, TC 27P IS EXPECTED TO MAKE LANDFALL OVER THE CAPE YORK PENINSULA AROUND TAU 24. UNTIL THEN, FAVORABLE ENVIRONMENTAL CONDITIONS WILL RESULT IN CONTINUOUS INTENSIFICATION. AS SOON AS THE LLCC AND THE ASSOCIATED EYEWALL HIT LAND, WEAKENING IS EXPECTED, WHICH WILL RESULT IN THE SYSTEM LOSING SOME OF ITS MOMENTUM. AS IT REEMERGES OVER THE GULF OF CARPENTARIA AROUND TAU 36, THE INTENSITY IS EXPECTED TO BE AT 65-70 KTS. AT THAT POINT, THE CORE OF THE VORTEX WILL BE SIGNIFICANTLY MORE BROAD THAN CURRENTLY OBSERVED. WITH THAT SAID, THE SYSTEM WILL REQUIRE SOME TIME TO CONSOLIDATE BEFORE IT INTENSIFIES AGAIN OVER THE FAVORABLE WATERS OF THE GULF. PEAK INTENSITY IS EXPECTED TO REACH 80-85 KTS BETWEEN TAUS 48 AND 72 AND PRIOR TO A SECONDARY LANDFALL IN THE VICINITY OF GROOTE EYLANDT. RAPID INTENSIFICATION DURING THAT PERIOD IS LESS LIKELY DUE TO INCREASING AND PERSISTENT EASTERLY VERTICAL WIND SHEAR, POTENTIALLY REACHING 30-35 KTS. AFTERWARDS, THE SYSTEM WILL TRACK OVER LAND FOR MAJORITY OF THE TIME, WITH A BRIEF TIME OVER THE JOSEPH BONAPARTE GULF BETWEEN TAUS 96 AND 120. AS A RESULT, A STEADY WEAKENING TREND IS EXPECTED THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS OVERALL IN VERY GOOD AGREEMENT REGARDING THE TRACK WITH NAVGEM BEING THE ONLY OUTLIER, AND PROJECTING A TRACK FURTHER SOUTH. THE ALONG-TRACK AND CROSS-TRACK SPREADS AMONG THE REMAINDER OF THE CONSENSUS MEMBERS ARE MINIMAL, RESULTING IN HIGH CONFIDENCE IN THE OFFICIAL JTWC TRACK PREDICTION. AS FAR AS INTENSITY, THE FORECAST IS LAID CLOSE AND SLIGHTLY ABOVE THE CONSENSUS AVERAGE, WITH MEDIUM CONFIDENCE. DETERMINISTIC GFS INTENSITY PREDICTION IS THE MAJOR OUTLIER OFFERING THE MOST CONSERVATIVE MAXIMUM WIND SPEEDS, WHILE NAVGEM-DRIVEN COAMPS- TC IS ON THE OTHER SIDE OF THE SPECTRUM, NOT INDICATING ANY LAND- INDUCED WEAKENING. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN