"It was a very, very powerful event," says Margaret Campbell-Brown, an astronomer at the University of Western Ontario in London, Canada, who has studied data from two infrasound stations near the impact site. Her calculations show that the meteoroid was approximately 15 metres across when it entered the atmosphere, and put its mass at around 7,000 metric tonnes. "That would make it the biggest object recorded to hit the Earth since Tunguska," she says.
2008 TC3 will become superheated as it strikes the thin upper atmosphere of the Earth to the point that it explodes far above the ground, probably at an altitude of tens of kilometers. This will occur high enough that no damage will occur on the ground. Some small fragments may survive and fall downrange (from Egypt and Sudan possibly to the Red Sea and Saudi Arabia) to reach the ground as meteorites. People over a large area should be able to see a spectacular fireball.
The Minor Planet Center gives about a 99.9% chance of 2008 TC3 encountering the Earth. JPL predicts that 2008 TC3 will enter the Earth's atmosphere over northern Sudan at 0246 GMT on 7 October (9:46 PM Central time 6 October). Impact point is predicted as 20.6° N, 33.1° E, at an angle of 18° above the horizon, by astronomers on the Minor Planets Mailing List bulletin board. This is approximate, and because of the low impact angle the fireball will pass over a significant downrange distance, moving west to east.