WTPN31 PGTW 182100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE WARNING// RMKS/ 1. TROPICAL DEPRESSION 18W (EIGHTEEN) WARNING NR 003 02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 181800Z --- NEAR 16.3N 108.1E MOVEMENT PAST SIX HOURS - 265 DEGREES AT 13 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT WIND RADII VALID OVER OPEN WATER ONLY REPEAT POSIT: 16.3N 108.1E --- FORECASTS: 12 HRS, VALID AT: 190600Z --- 15.9N 106.1E MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND VECTOR TO 24 HR POSIT: 260 DEG/ 06 KTS --- 24 HRS, VALID AT: 191800Z --- 15.7N 104.8E MAX SUSTAINED WINDS - 015 KT, GUSTS 025 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND --- REMARKS: 182100Z POSITION NEAR 16.2N 107.6E. TROPICAL DEPRESSION 18W (EIGHTEEN), LOCATED APPROXIMATELY 21 NM NORTH-NORTHWEST OF DA NANG, VIETNAM, HAS TRACKED WESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY REVEALS A BROAD AND POORLY DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FLARING DEEP CONVECTION SHEARED TO THE WEST OF THE LLCC. A 181433Z AMSU-B MICROWAVE IMAGE FURTHER REVEALS THE BROAD NATURE OF THE SYSTEM AS WELL AS INDICATES THE BULK OF THE DEEP CONVECTION IS SIGNIFICANTLY SHEARED OVER LAND. THE INITIAL POSITION IS BASED ON THE IR LOOP AND AFOREMENTIONED MICROWAVE IMAGE WITH POOR CONFIDENCE. A RECENT SCATTEROMETRY PASS INDICATES A SMALL LLCC, JUST EAST OF VIETNAM, WITH 20 KNOT WIND BARBS SURROUNDING THE CORE AND 25 KNOT BARBS ACROSS THE NORTHERN SEMICIRCLE. THE CURRENT INTENSITY IS ASSESSED AT 25 KNOTS BASED UPON OBSERVATIONS IN THE AREA AND DVORAK INTENSITY ESTIMATES OF 25 KNOTS FROM PGTW AND KNES. UPPER LEVEL ANALYSIS REVEALS THE SYSTEM IS LOCATED JUST EQUATORWARD OF THE SUBTROPICAL RIDGE AXIS IN A REGION OF MODERATE VERTICAL WIND SHEAR (15 TO 20 KNOTS) AND EASTERLY DIFFLUENT OUTFLOW. TD 18W IS FORECAST TO MOVE OVER LAND AND SUCCUMB TO INCREASING VWS AND THE FRICTIONAL EFFECTS OF LAND, ULTIMATELY DISSIPATING OVER THE NEXT 12 HOURS. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 181800Z IS 8 FEET. REFER TO TYPHOON 17W (USAGI) WARNINGS (WTPN32 PGTW) FOR SIX-HOURLY UPDATES. // NNNN