For the next day-and-a-half, Leslie meandered over the north Atlantic without any change in intensity. At 09:00 UTC on 1 October it began to strengthen, with the NHC noting an increase in convective banding in the north and northwest.[18] Leslie continued to slowly strengthen over the next couple of days, before becoming a hurricane on 3 October at 09:00 UTC.[19] At that time, deep convection surrounding Leslie had immensely improved and a well-defined low-level eye had developed.