Tropical Cyclone Weekly Summary #7 (September 15 - 22, 1991) This report is compiled from warnings issued by: National Hurricane Center Central Pacific Hurricane Center Joint Typhoon Warning Center Japanese Meteorological Agency Royal Observatory of Hong Kong Indian Meteorological Service Reunion Meteorological Service (others may be added as they become available) WEEKLY TROPICAL CYCLONE SUMMARY #7: SEPTEMBER 15 - 22, 1991 North Atlantic Basin: No tropical cyclones. Eastern North Pacific Basin (E of 140 Deg. W): Tropical Storm Ignacio: Tropical Depression 11E formed near 14N 102W on 16 September. The system intensified to Tropical Storm Ignacio the same day while moving north-northwest. Ignacio reached a peak intensity of 50 kt on 17 September. Rapid weakening then ensued, and Ignacio dissipated near 17N 103W on 18 September. Hurricane Jimena: Tropical Depression 12E formed near 10N 100W on 20 September. Moving west-northwest, the system became Tropical Storm Jimena the next day. Jimena reached hurricane intensity on 22 September, and at at the end of the summary period it was moving west with 70 kt winds. Central North Pacific Basin (180 Deg. W to 140 Deg. W): No tropical cyclones. Western North Pacific Basin (W of 180 Deg. W): Tropical Storm Luke: At the start of the summary period, Tropical Storm Luke was tracking west-northwestward with 40 kt winds. Luke turned north- west on 16 September, and then it recurved to the northeast on 18 Septem- ber. Maximum winds reached 55 kt on 19 September, and the system became extratropical on 20 September. It should be noted that Typhoon Ivy, Typhoon Kinna, and Tropical Storm Luke have all become very powerful extratropical low pressure systems that moved into the Aleutian Islands. Typhoon Mireille: The tropical depression that was mentioned in summary #6 near 14N 165E intensified very rapdily as it became first Tropical Storm Mireille and then Typhoon Mireille on 16 September. Developement was in- terrupted at that point, and winds remained in the 65 to 80 kt range as the typhoon moved west thru 19 September. Mireille passed just north of Saipan in the Marianas Islands on 19 September, and typhoon force winds were not observed at the weather station. Mireille started to intensify again on 20 September, and winds increased to 130 kt as the typhoon turned west- northwest. At the end of the summary period, Mireille was moving northwest while maintaining its 130 kt winds. Typhoon Nat: The tropical depression that was mentioned in summary #6 near 16N 133E developed into Tropical Storm Nat on 16 September. Erratic motion was a characteristic of this storm. It was moving west when it first reached tropical storm intensity. On 17 September, it drifted erratically near 20N 118E. On 18 September, it started drifting eastward. An east to east-northeast motion persisted through 20 September. On 21 September, Nat started moving in a genally westward direction again. Intensification was slow until 21 September, when Nat quickly strengthened into a typhoon. At the end of the summary period, Nat was moving westward toward southern Tai- wan with 110 kt winds. North Indian Ocean Basin: No tropical cyclones. South Indian Ocean Basin (W of 135 Deg. E): No tropical cyclones. South Pacific Ocean Basin (E of 135 Deg. E): No tropical cyclones. Disclaimer: While an effort has been made to make sure this information is accurate as possible, it was drawn from operational warnings that may not always agree with the best track information published after the storm is over. Please address any questions or comments by e-mail to: jack@cloud3.met.fsu.edu.