another weakness

The wind turbines were spinning making a sound like the laughter of skulls.
Accelerator was making that plasma by compressing the wind he gathered from
throughout the city. The scale was much too small for him to be gathering it from
throughout the world, so his ability must have had limits.

For example, when he was controlling rather than just reflecting, he might have to
calculate out the original vector for the wind as well as the altered vector.
In that case, his calculations could be interrupted by something causing a disturbance in
the wind throughout the city.
Academy City had wind turbines spread throughout the city. There were probably more
than 10,000 of them.
And the wind turbines could be made to spin by using a certain electromagnetic wave.
Each individual propeller could only produce a small amount of wind, but more than
10,000 of them spinning at once was a different story. Accelerator may lose control of
the wind as a result.

- Toaru Majutsu no Index Volume 3, Chapter 4 Part 7


With a roar of wind, the sphere of plasma floating above lost its form.
“Wha-...?”
Accelerator looked up. That plasma had been created from all the wind flowing through
the city being condensed into one point. The flow of that wind had clearly shaken for an
instant. That had caused an error in the compression ratio which caused the plasma to
be shaken as well.
Accelerator thought he might have made an error in his calculations of the wind, so he
rebuilt those new equations. Unlike simple reflection, he had to calculate both, the
vector before alteration and the vector after alteration which was a pain in the ass.
But Accelerator managed to perfectly revise that huge set of equations in less than 10
seconds. His brain had developed to the point that something of that level was no
problem. In Academy City, power development was part of the teaching method, so
Academy City’s strongest espers were also Academy City’s greatest honor students.
But the movement of the wind flowing through the city suddenly changed as if escaping
from the supposedly perfect equations he had built up in his head. It was not a mere
coincidence. It was as if the wind itself had a will and was slipping through the gaps of
his equations.
The mass of compressed air above his head scattered and the plasma disappeared as if it
were dissolving into the air.

- Toaru Majutsu no Index Volume 3, Chapter 4 Part 8