Although NASA has cleared Space Shuttle Atlantis to launch after checking its systems for the impact of a lightning strike on 25 August, the proximty of tropical storm Ernesto to Kennedy Space Center could see the shuttle rolled back to the vehicle assembly building (VAB) for safety reasons.
During a Sunday 27 August press conference, space shuttle programme launch integration manager LeRoy Cain said "[I'm] happy to report that the team has finished their lightning strike reviews, and the vehicle has been cleared for launch."

But preliminary preparations are today under way to roll Atlantis back to the VAB, although no final decision has been made to allow for possible changes in tropical storm Ernesto's track. The roll back decision is expected by midday, local time, Tuesday 29 August.

Atlantis rolls from the VAB for STS-115

 Above: Atlantis on the mobile transporter with launch pad 39B in the background

Cain added that management and engineering teams had spent Sunday tracking two major issues, the impact of the lightning strike and the intensity and direction of tropical storm Ernesto. The launch window extends until 13 September but mission managers are hoping to launch by 7 September. 

A launch from the ninth to the 13 September would see the Shuttle, which has an 11-day mission planned, at the International Space Station (ISS) at the same time as the expected arrival of a Soyuz spacecraft, which is to be launched on 18 September. NASA is discussing the scheduling conflict issue with the Russian Federal Space Agency.

Mission Atlantis/STS-115 will see astronauts install the  P3/P4 integrated truss and a second set of solar arrays on the ISS, doubling the station’s current ability to generate power from sunlight and adding 15.8t to its mass.