WTXS31 PGTW 180900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 21S (GUAMBE) WARNING NR 002// RMKS/ 1. TROPICAL CYCLONE 21S (GUAMBE) WARNING NR 002 01 ACTIVE TROPICAL CYCLONE IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 180600Z --- NEAR 22.6S 37.7E MOVEMENT PAST SIX HOURS - 155 DEGREES AT 04 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 030 NM NORTHEAST QUADRANT 035 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 035 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 110 NM NORTHEAST QUADRANT 100 NM SOUTHEAST QUADRANT 095 NM SOUTHWEST QUADRANT 105 NM NORTHWEST QUADRANT REPEAT POSIT: 22.6S 37.7E --- FORECASTS: 12 HRS, VALID AT: 181800Z --- 23.2S 37.7E MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 040 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT 130 NM SOUTHEAST QUADRANT 090 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 225 DEG/ 04 KTS --- 24 HRS, VALID AT: 190600Z --- 23.8S 37.0E MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 020 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 130 NM NORTHEAST QUADRANT 140 NM SOUTHEAST QUADRANT 150 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 215 DEG/ 06 KTS --- 36 HRS, VALID AT: 191800Z --- 24.7S 36.3E MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 060 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT 140 NM SOUTHEAST QUADRANT 150 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 200 DEG/ 05 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 200600Z --- 25.6S 35.9E MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 050 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 070 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 070 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 110 NM NORTHEAST QUADRANT 150 NM SOUTHEAST QUADRANT 130 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 155 DEG/ 08 KTS --- 72 HRS, VALID AT: 210600Z --- 28.5S 37.4E MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 050 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 070 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 070 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT 140 NM SOUTHEAST QUADRANT 150 NM SOUTHWEST QUADRANT 120 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 125 DEG/ 16 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 220600Z --- 32.0S 43.8E MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING EXTRATROPICAL RADIUS OF 064 KT WINDS - 040 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 080 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 150 NM NORTHEAST QUADRANT 180 NM SOUTHEAST QUADRANT 210 NM SOUTHWEST QUADRANT 160 NM NORTHWEST QUADRANT VECTOR TO 120 HR POSIT: 110 DEG/ 20 KTS --- 120 HRS, VALID AT: 230600Z --- 34.7S 52.9E MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY EXTRATROPICAL RADIUS OF 050 KT WINDS - 080 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 150 NM NORTHEAST QUADRANT 180 NM SOUTHEAST QUADRANT 210 NM SOUTHWEST QUADRANT 160 NM NORTHWEST QUADRANT --- REMARKS: 180900Z POSITION NEAR 22.8S 37.7E. 18FEB21. TROPICAL CYCLONE 21S (GUAMBE), LOCATED APPROXIMATELY 141 NM WEST OF EUROPA ISLAND, HAS TRACKED SOUTH-SOUTHEASTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A STEADILY IMPROVING CONVECTIVE SIGNATURE WITH WEAK CYCLONIC BANDING FEATURES BECOMING EVIDENT WITHIN THE CENTRAL DENSE OVERCAST (CDO) WHICH IS OBSCURING THE LOW LEVEL CIRCUATION CENTER (LLCC). IN LIGHT OF THE OBSCURATION OF THE LLCC AND THE LACK OF RECENT HIGH RESOLUTION MICROWAVE IMAGERY, THOUGH AN ANALYSIS OF WEAK LOW-LEVEL BANDING FEATURES IN AN 180348Z N-19 89GHZ COMPOSITE IMAGE, LENT MODERATE CONFIDENCE TO THE INITIAL POSITION THE INITIAL INTENSITY IS ASSESSED AT 50 KTS WITH HIGH CONFIDENCE BASED ON AN AVERAGE OF MULTI-AGENCY DVORAK CURRENT INTENSITY ESIMATES RANGING FROM T2.5 (35KTS, PGTW) TO 3.5 (55KTS, FMEE), AND AN ADT ESTIMATE OF T3.3. ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS WITH A DEVELOPING POINT SOURCE DIRECTLY OVER THE LLCC PROVIDING LOW (5-10 KTS) VWS, MODERATE TO STRONG, NEARLY RADIAL OUTFLOW AND WARM (29- 30C) SSTS. TC 21S IS CURRENTLY ENSCONCED BETWEEN A BUILDING SUBTROPICAL RIDGE (STR) CENTER OVER NORTHERN MADACASGAR AND A SECONDARY STR CENTER OVER NORTHERN SOUTH AFRICA, RESULTING IN SLOW MOVEMENT SOUTHWARD. OVER THE NEXT 12-24 HOURS, THE EASTERN STR IS EXPECTED TO BUILD SUFFICIENTLY TO BECOME THE DOMINATE STEERING MECHANISM AND TURN TC 21S TO A WEST-SOUTHWESTWARD TRACK. AS THE STR MOVES SOUTH-SOUTHEASTWARD THROUGH TAU 48, TC 21S WILL ACCELERATE SOUTH THEN SOUTHEASTWARD AS IT ROUNDS THE RIDGE AXIS. AFTER TAU 72 THE SYSTEM RAPIDLY ACCELERATES SOUTHEASTWARD ALONG THE BAROCLINIC ZONE AS IT BEGINS TO INTERACT WITH STRONG MID-LATITUDE WESTERLY FLOW ALOFT. TC 21S IS EXPECTED TO STEADILY INTENSIFY UNDER FAVORABLE CONDITIONS TO A PEAK OF 85 KTS BY TAU 48, THEN MAINTAIN INTENSITY THROUGH TAU 72. THEREAFTER, INCREASING VWS WILL OFFSET THE STRONG POLEWARD OUTFLOW, LEADING TO SLOW WEAKENING. TC 21S WILL BEGIN EXTRATROPICAL TRANSITION BY TAU 96, AND BECOME A STORM-FORCE EXTRATROPICAL SYSTEM BY TAU 120. ALL MEMBERS OF THE CONSENSUS CONCUR ON THE OVERALL SCENARIO BUT DISPLAY SIGNIFICANT CROSS TRACK UNCERTAINTY THOUGH TAU 48, WITH NAVGEM AND THE COAMPS-TC TAKING THE SYSTEM MUCH CLOSER TO THE COAST OF MOZAMBIQUE, AND THE GFS AND ECMWF KEEPING THE SYSTEM WELL OFFSHORE IN THE MOZAMBIQUE CHANNEL. AFTER TAU 72, THE PACE AND STRENGTH OF THE INTERACTION WITH THE WESTERLIES RESULT IN EXTREMELY LARGE ALONG-TRACK UNCERTAINTY, WITH THE GFS, UKMET AND ECMWF WELL OUT AHEAD (800NM) OF THE REMAINING MEMBERS OF THE CONSENSUS. THE JTWC FORECAST TRACKS CLOSE TO THE ECMWF THROUGH TAU 48, BUT CLOSER TO THE NAVGEM THROUGH TAU 120. OVERALL THE JTWC FORECAST IS MUCH FASTER AFTER TAU 72 THAN THE PREVIOUS FORECAST. DUE TO THE VERY HIGH UNCERTAINTY IN THE LATER PORTIONS OF THE FORECAST, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 180600Z IS 18 FEET. NEXT WARNINGS AT 182100Z AND 190900Z.// NNNN