Warnings ARE possible. After the initial earthquake, it can be several hours before the tsunami hits a distant coast. Wave front moves 500 to 600 mph (800 to 1000 km/h) in water.
Warnings ARE possible.
I knew about the warning system but had forgotten just how incredibly fast the waves can move. To be a little more clear, I should have said 'immediate natural environment'. Was thinking in my Oklahoma tornado context. Having lived a lot of my life in OK, one's internal radar can sense that conditions are 'ripe' for tornadic activity hours before the wall cloud appears outside your window & the television screen lights up w/ warnings.