Right, so probably, the mechanism that would cause such a rainfall, coming from the oceans waters as I am proposing, would carry with it a lot of heat, and do the same thing. Then all that heat from kinetic energy of a raindrop falling would be a non-issue.
I think, without bothering to calculate it out, that the heat from kinetic energy probably isn't the big player here. Far more important in any *worldwide* flood is the means to drive such a huge heat engine
everywhere at once. If it's raining all over the world (that was a song once, I think....) you must provide 540 calories of heat per gram of water you evaporate on the surface, you must get rid of that same 540 calories per gram up in the clouds as you recondense that vapor,
and you somehow must transport the vapor up through the falling rain to where it can make more raindrops!
And the size of this heat flow ain't 'zactly small - if we take your 4 inches of rain per hour, I calculate 100,000 grams of water per hour for each square meter of the Earth's surface. That comes to 54,000,000 calories for each of the (several!) square meters on Earth, each hour for forty days and forty nights, getting transferred from rock to water, and then from water vapor to outer space. In (physically) countercurrent flow. (I don't remember what calories come out to in Btu's, RR. Sorry.)
Hurricane Ivan didn't have this problem. He was only a couple of hundred miles across, and had the whole warm Caribbean to wander on and suck heat and water vapor from. I'll bet, though, that the heat flow problems are precisely what keeps hurricanes from getting larger than they do - the physics of our atmosphere just won't allow them to.
A cumulonympho? That's a f***ing thunderstorm!