It would be beyond prediction without resorting to heavy duty computer simulations, and even then the results would be pretty iffy.
The big problem is that a lot of the oceanic current
heat transport mechanisms would be affected since the underwater topography would have changed a fair bit, places that were land and couldn't transport water
and heat now could.
The cycles that involve airborne heat transport between land and sea areas would be completely disrupted. Take for instance the monsoons, as wikipedia describes them they are 'seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating
of land and sea.' ( Monsoon - Wikipedia, the free encyclopedia
You may ask what does heat transport have to do with the weather? It has everything to do with the weather, the difference in temperature between various locations on the surface of the earth provides the energy to drive winds, and related temperature and pressure changes lead to rain.
Even now the best models running on the really big computers
are only good for predicting 48hr or so in advance and that is after decades of refinement, coparing predictions to actual weather in order to find refinements.