"water vapor comes and goes with the weather."

Yes, but now we are talking about combusting H2 with O2, which is an entirely new source of H2O vapor.

And, if you want another little problem to solve with the storage and use of hydrogen, look up "Hydrogen Embrittlement."

I'm not saying it won't be feasible, but it isn't by any means a magic panacea.

In his book, "Skunk Works," Ben Rich talks about Lockheed's experiments with producing and storing liquid hydrogen in the 1950's for possible use as a fuel for high flying, Mach 3+ reconnaissance aircraft. The chapter is titled "Blowing Up Burbank." (That should give you a hint.) Their conclusions were that it was terribly inefficient due to the size of the storage vessel needed for acceptable range, it was very dangerous to transport and store and the infrastructure needed to ensure availability around the world would cost more than the rest of the program, including development of the aircraft and training Air Force personnel to handle it. They went with a new fuel (JP-7) and built the A-12, followed by the SR-71.