WTXS31 PGTW 280900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 07S (CHALANE) WARNING NR 008// RMKS/ 1. TROPICAL CYCLONE 07S (CHALANE) WARNING NR 008 01 ACTIVE TROPICAL CYCLONE IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 280600Z --- NEAR 20.0S 43.7E MOVEMENT PAST SIX HOURS - 245 DEGREES AT 09 KTS POSITION ACCURATE TO WITHIN 040 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 000 NM NORTHEAST QUADRANT 025 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT REPEAT POSIT: 20.0S 43.7E --- FORECASTS: 12 HRS, VALID AT: 281800Z --- 20.2S 42.1E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 060 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 275 DEG/ 09 KTS --- 24 HRS, VALID AT: 290600Z --- 20.1S 40.2E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 270 DEG/ 10 KTS --- 36 HRS, VALID AT: 291800Z --- 20.0S 38.0E MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 000 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 010 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 270 DEG/ 11 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 300600Z --- 20.0S 35.7E MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 000 NM NORTHEAST QUADRANT 010 NM SOUTHEAST QUADRANT 000 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 000 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 010 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 265 DEG/ 12 KTS --- 72 HRS, VALID AT: 310600Z --- 20.2S 30.5E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND VECTOR TO 96 HR POSIT: 265 DEG/ 13 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 010600Z --- 20.5S 24.9E MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND --- REMARKS: 280900Z POSITION NEAR 20.1S 43.3E. 28DEC20. TROPICAL CYCLONE 07S (CHALANE), LOCATED APPROXIMATELY 236 NM EAST-NORTHEAST OF EUROPA ISLAND, HAS TRACKED WEST- SOUTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CONVECTION FLARING TO THE NORTHWEST AND OVER THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH THE LOW LEVEL CLOUD BANDS EXPOSED ON THE SOUTHERN SIDE. ANALYSIS OF THE EXPOSED LOW LEVEL CLOUD BANDS, AND A 280550Z ASCAT-A SCATTEROMETER PASS LEND HIGH CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY IS HEDGED SLIGHTLY HIGHER THAN THE PGTW DVORAK INTENSITY ESTIMATE OF T1.5 (25 KTS) BASED ON AN ADT ESTIMATE OF T2.5 (35 KTS), A SATELLITE CONSENSUS ESTIMATE OF 36 KTS AND THE AFOREMENTIONED 280550Z ASCAT-A PASS, WHICH SHOWED A BAND OF 30-35 KNOT WINDS STRETCHING FROM THE NORTHEAST TO SOUTHEAST QUADRANTS, BETWEEN THE LLCC AND THE COASTLINE. ENVIRONMENTAL ANALYSIS REVEALS GENERALLY SUPPORTIVE CONDITIONS, WITH LOW (<10 KTS) VWS, AND VERY WARM (31-32C) SSTS, BEING OFFSET SOMEWHAT BY WEAK OUTFLOW ALOFT, AS THE SYSTEM LIES DIRECTLY ALONG THE AXIS OF A 200 MB RIDGE EXTENDING FROM FAR NORTHERN SOUTH AFRICA TO NORTHEAST MADAGASCAR. TC 07S CONTINUES TO TRACK WEST-SOUTHWESTWARD ALONG THE NORTHWESTERN PERIPHERY OF A LOW TO MID-LEVEL STR LOCATED TO THE SOUTHEAST OF MADAGASCAR. OVER THE NEXT 12 HOURS, THE STEERING PATTERN IS EXPECTED TO CHANGE, WITH A BUILDING STR TO THE SOUTH OF THE MOZAMBIQUE CHANNEL EXPECTED TO PRESUME THE DOMINANT STEERING ROLE, SHIFTING TC 07S TO A WESTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST. NUMERICAL TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH THE ENTIRETY OF THE FORCAST PERIOD, WITH A MAXIMUM SPREAD OF 90NM AT TAU 48, LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK. THERE IS HOWEVER SIGNIFICANT UNCERTAINTY IN THE INTENSITY GUIDANCE, WITH THE HWRF NOW BACKING OFF THE RAPID INTENSIFICATION IT HAS BEEN PREDICTING IN EARLIER RUNS, WHILE THE ECMWF AND COAMPS-TC SOLUTIONS CONTINUE TO SHOW A PEAK INTENSITY NEAR 55 KNOTS. IN THE NEAR-TERM, WEAK OUTFLOW AND MID-LEVEL DRY AIR WILL LIMIT THE OPPORTUNITY FOR INTENSIFICATION THROUGH TAU 24. THERAFTER THE MID-LEVELS MOISTEN, OUTFLOW SLOWLY IMPROVES AND THE SYSTEM MOVES OVER A POOL OF HIGH OHC, ALLOWING FOR FASTER INTENSIFICATION THROUGH TAU 36. THE SYSTEM IS EXPECTED TO REACH PEAK INTENSITY OF 65 KNOTS AT TAU 48 AS IT MOVES THROUGH A VERY FAVORABLE ENVIRONMENT. THE ONLY FACTOR LIMITING THE INTENSIFICATION IS THE AMOUNT OF OUTFLOW ALOFT, AND ANALYSIS OF UPPER-LEVEL MODEL FIELDS LENDS SUPPORT TO A HIGHER INTENSITY THAN THE INTENSITY GUIDANCE WOULD SUGGEST. THE COAMPS-TC ENSEMBLE SUGGESTS A HIGH PROBABILITY OF INTENSIFICATION UP TO 65 KNOTS, WITH A SLIGHT POSSIBILITY OF A HIGHER INTENSITY JUST PRIOR TO LANDFALL NEAR BEIRA, MOZAMBIQUE. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 280600Z IS 12 FEET. NEXT WARNINGS AT 282100Z AND 290900Z.// NNNN