The OP is quite interesting, never actually seen this kind of theory before.
But I do think that this is most likely moving closer to the actual explanation (Ronald's response).
It can be hard to understand what is going on with end-time prophecies relating to the state of the earth, but if you do a little scientific research you can get an idea. The 6th Seal and 7th Bowl are similar, of which reflect what was prophesied by Isaiah. I think this is the primary explanation.
Isaiah 24:19-21 New American Standard Bible (NASB)
19 The earth is broken asunder,
The earth is split through,
The earth is shaken violently.
20 The earth reels to and fro like a drunkard
And it totters like a shack,
For its transgression is heavy upon it,
And it will fall, never to rise again.
21 So it will happen in that day,
That the Lord will punish the host of heaven on high,
And the kings of the earth on earth.
The hailstones are one of several results of this reeling, the most significant one being the shortening of the days from 24 to 16 hours (Trumpet 5) which can be again be explained using science (conservation of momentum for a rotating body).
But on the hail stones, the violent shaking of the earth is going to cause an unprecedented evaporative effect worldwide (mostly of the oceans). Remember 71% of earth is covered in water. Coupled with the atmospheric convulsions that will be going on at that time (inside air currents and drafts being generated), you'll essentially have "oceans" of water in the atmosphere being cooled to astronomical degrees, hence the gigantic hailstones.