I would argue that it is not obvious. The impact of ships on low level liquid clouds is a very different process and is comparatively well understood. There is even a wikipedia article on it [1]
However, convective invigoration by aerosols is a different issue. They are suggestions that suppressing warm rain (rain formed through processes that don't involving ice) might lead to more intense updraughts in convective systems [2], but the observational evidence is unclear. Convective storms tend to form in humid locations, where satellite observations of aerosol are biased high by the humidity [3].
Even in this case, it is not clear that the result holds outside the local aerosol enhancement generated by ships [4]. Do aerosols affect convective clouds at a large scale? I would argue that there is no strong evidence either way at the moment.
[1] - https://en.wikipedia.org/wiki/Ship_tracks
[2] - http://doi.org/10.1126/science.1160606