CHARLOTTE, NC (WBTV) - Every so often someone will ask me why the rain from tropical systems do not produce salty rain water since their origins are over the ocean and they clearly derive their moisture from that source.
I don't think anyone would argue the point that the vast majority of moisture that makes up the clouds and storms in hurricanes is supplied by the ocean. But it is important to keep in mind the exact process of how the moisture is transported from the ocean up into the atmosphere where the clouds and eventually the rain form.
Unlike tornadoes which can actually suck water straight up into the storm and, yes, deposit the salty water in another place, hurricanes don't posses that funnel type forcing on a broad scale. Instead, the moisture that feeds the hurricane's clouds occurs purely from evaporation.
As the ocean water evaporates into water vapor, a gas, the salt itself is left behind in the ocean.
Thus, all that remains is the pure water vapor which eventually condenses back into a cloud droplet. Any rain that might fall from that would also be salt-free water.