WTXS31 PGTW 170900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 10S (JOSHUA) WARNING NR 004// RMKS/ 1. TROPICAL CYCLONE 10S (JOSHUA) WARNING NR 004 02 ACTIVE TROPICAL CYCLONES IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 170600Z --- NEAR 18.4S 89.9E MOVEMENT PAST SIX HOURS - 235 DEGREES AT 09 KTS POSITION ACCURATE TO WITHIN 030 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 - 050 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 070 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT REPEAT POSIT: 18.4S 89.9E --- FORECASTS: 12 HRS, VALID AT: 171800Z --- 18.9S 88.5E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 020 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 255 DEG/ 08 KTS --- 24 HRS, VALID AT: 180600Z --- 19.3S 86.8E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 020 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 265 DEG/ 09 KTS --- 36 HRS, VALID AT: 181800Z --- 19.5S 85.0E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 080 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 070 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 260 DEG/ 10 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 190600Z --- 19.8S 82.9E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 034 KT WINDS - 080 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 070 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 255 DEG/ 10 KTS --- 72 HRS, VALID AT: 200600Z --- 20.7S 78.7E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 034 KT WINDS - 080 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 070 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 250 DEG/ 09 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 210600Z --- 21.8S 75.2E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 170900Z POSITION NEAR 18.5S 89.5E. 17JAN21. TROPICAL CYCLONE (TC) 10S (JOSHUA), LOCATED APPROXIMATELY 1222 NM SOUTHEAST OF DIEGO GARCIA, HAS TRACKED SOUTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A SLOWLY-CONSOLIDATING SYSTEM WITH DEEP CONVECTIVE BANDING OVER THE WESTERN SEMICIRCLE WRAPPING INTO A WEAKLY DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). A 170326Z MHS 89GHZ IMAGE REVEALS LIMITED, FRAGMENTED DEEP CONVECTIVE BANDING AND SHALLOW BANDING WRAPPING INTO A DEFINED LLCC, WHICH SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH WEAK POLEWARD OUTFLOW, LOW NORTHEASTERLY VERTICAL WIND SHEAR (VWS) AND CONDUCIVE SST VALUES (26-27C). THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON THE PGTW DVORAK CURRENT INTENSITY ESTIMATE OF 2.5 (35 KNOTS) AND A 170600Z ADT ESTIMATE OF 2.4. TC 10S IS EXPECTED TO TRACK WESTWARD TO WEST-SOUTHWESTWARD THROUGH THE FORECAST PERIOD ALONG THE NORTHERN FLANK OF A LOW-LEVEL SUBTROPICAL RIDGE. WITH THE EXCEPTION OF NVGI AND EGRI, WHICH TURN THE SYSTEM SOUTHWARD AFTER TAU 72, THE BULK OF THE GUIDANCE IS IN GOOD AGREEMENT WITH A 110- 150NM SPREAD IN SOLUTIONS AFTER TAU 72. CONSEQUENTLY, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK. TC 10S IS FORECAST TO INTENSIFY SLIGHTLY TO 40 KNOTS BY TAU 12 BUT WILL WEAKEN STEADILY AFTER TAU 36 DUE TO INCREASING VWS, COOLER SST VALUES (25-26C), WEAK OUTFLOW AND DRY AIR ENTRAINMENT. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 170600Z IS 14 FEET. NEXT WARNINGS AT 172100Z AND 180900Z. REFER TO TROPICAL CYCLONE 12S (ELOISE) WARNINGS (WTXS32 PGTW) FOR TWELVE- HOURLY UPDATES.// NNNN