The TV news reporters are reporting that Tsunami waves are due to hit Hawaii within the half hour - at 1307 UTC (0307 HST). This is both true and not true. This is the earliest expected arrival time. The actual wave may not hit exactly on the mark, and in either case this is the time that waves are due to hit the westernmost coasts of Kauai. The wave will not hit the entire state instantaneously - it will take over an hour for the waves to travel down the rest of the chain.
We know that the wave was very destructive near the epicenter of the earthquake, but that does not necessarily mean that it will be as destructive in distant areas. Because the earthquake took place in Japan, and because there is little between there and Honolulu except the ocean, it is hard to predict exactly what will happen. Instrumentation at Midway indicates that the wave was approximately 5 feet above normal sea level there.
For twitter coverage, see hashtag #hitsunami