Brain Freeze

The copies are put directly onto the stack. They aren't cast and won't be counted by other spells with storm cast later in the turn.

A copy of a spell can be countered like any other spell, but it must be countered individually. Countering a spell with storm won't affect the copies.

The triggered ability that creates the copies can itself be countered by anything that can counter a triggered ability. If it is countered, no copies will be put onto the stack.