The other day as my wife and I were going over the checkbook in the dining room one of our daughters, in the west-facing living room, called us to come look at the sky. She saw how the clouds' ragged edges took light from the sun, intensifying both the dark gray of the main body of the clouds and the pale blue of the late autumn sky. She was touched by the lovely picture it all made. She felt that we should see the sky for ourselves, should share directly the experience that triggered her feelings. So she called us.
As we looked at the sky, we saw what she saw. And at the same time we thought back to other skies we had known. I felt the mixed feelings of time passing, the loss of the heat of summer and the beginning of the rush toward the winter holidays and the New Year. My wife spoke of the deeper colors that would come later, with the reddening of the sunset. As the three of us looked at the sky, almost wordlessly, we felt a sharing that goes far deeper than the words I have just used to describe the event can ever penetrate. (4-5)
So it is indeed the sense of recognition which is important, and the sharing of that moment between haiku writer and haiku reader.
The process may be put like this: event (can be natural, social, or whatever) is seen/experienced; writer uses the medium of haiku to translate the "aha" experience in a very short but very suggestive way, effacing him/herself behind it; reader reads haiku and, if it is a successful one, will almost get the event in its original impact and (hopefully) experience the "aha" moment, albeit in a slightly different, and specifically personal manner.
Now, whether it is actually possible to transport the same moment even when the actual event is not there anymore is of course open to discussion, but it is admirable that the haiku at least tries to do so with such an economy of words and with such evocative power.