Microwave data showed that the system had a surface circulation elongated around an intruding baroclinic zone.[11] At 18:00 UTC on 25 September, the NHC forecasted that Leslie would regain subtropical characteristics in a couple days.[12] Soon afterward, Leslie merged with an approaching frontal system and subsequently strengthened; on 27 September, at 00:00 UTC, Leslie acquired hurricane-force winds, due to baroclinic processes.[13] As Leslie began to regain subtropical characteristics, it weakened to tropical storm force strength.[14] At 21:00 UTC on 28 September, the NHC resumed issuing advisories on Leslie as a subtropical storm, as its organization had increased and baroclinic features had disappeared.[15]