WTXS31 PGTW 181500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 10S (JOSHUA) WARNING NR 007// RMKS/ 1. TROPICAL CYCLONE 10S (JOSHUA) WARNING NR 007 02 ACTIVE TROPICAL CYCLONES IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 181200Z --- NEAR 19.5S 86.3E MOVEMENT PAST SIX HOURS - 270 DEGREES AT 08 KTS POSITION ACCURATE TO WITHIN 045 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 035 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 045 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT REPEAT POSIT: 19.5S 86.3E --- FORECASTS: 12 HRS, VALID AT: 190000Z --- 19.3S 84.4E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 010 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 265 DEG/ 11 KTS --- 24 HRS, VALID AT: 191200Z --- 19.4S 82.1E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 030 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 245 DEG/ 11 KTS --- 36 HRS, VALID AT: 200000Z --- 20.3S 79.9E 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 - 030 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 250 DEG/ 11 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 201200Z --- 21.1S 77.7E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 181500Z POSITION NEAR 19.4S 85.8E. 18JAN21. TROPICAL CYCLONE (TC) 10S (JOSHUA), LOCATED APPROXIMATELY 1095 NM SOUTHEAST OF DIEGO GARCIA, HAS TRACKED WESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY REVEALS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) POSITIONED ON THE NORTHWEST EDGE OF AN AREA OF PERSISTENT DEEP CONVECTION. AN 181111Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTS SHALLOW BANDING WRAPPING INTO THE LLCC, WHICH IS JUST LOCATED UNDER A WEAK CURVED BAND OF DEEP CONVECTION. THE INITIAL INTENSITY IS ASSESSED AT 40 KNOTS BASED ON AN AVERAGE OF THE PGTW/FMEE CURRENT INTENSITY ESTIMATES RANGING FROM 2.5-3.0 (35-45 KNOTS). ENVIRONMENTAL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR, FAIR POLEWARD OUTFLOW AND MARGINAL SST VALUES (26C). HOWEVER, ANIMATED WATER VAPOR IMAGERY INDICATES AN UPPER-LEVEL SHORTWAVE TROUGH IS IMPINGING ON THE WESTERN PERIPHERY OF THE SYSTEM. ADDITIONALLY, THERE IS EVIDENCE OF SIGNIFICANT DRY AIR ENTRAINMENT, WHICH WILL LEAD TO STEADY WEAKENING. TC 10S IS FORECAST TO TRACK WESTWARD TO WEST-SOUTHWESTWARD ALONG THE NORTHWEST PERIPHERY OF A LOW-LEVEL SUBTROPICAL RIDGE AND IS EXPECTED TO DISSIPATE BY TAU 48. NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 181200Z IS 15 FEET. NEXT WARNINGS AT 190300Z AND 191500Z. REFER TO TROPICAL CYCLONE 12S (ELOISE) WARNINGS (WTXS32 PGTW) FOR TWELVE-HOURLY UPDATES.// NNNN