Is it possible? Probably yes. It depends on how you’re deforming the mesh.
If you’re using math functions, the normal of a curve can be found mathematically also.
Here’s a forum post that discusses solving for the normal of a point on a sine wave, for example.
https://gamedev.net/forums/topic/551569-finding-the-normal-of-a-point-on-a-sine-wave/551569/
“Sine curve is parameterized as (x,sin(x)). A unit-length tangent is (1,cos(x))/sqrt(1+(cos(x))^2) = (tx,ty). A unit-length normal is (ty,-tx).”
In other words, it comes down to solving for the functions tangent, and then rotating the tangent 90 degrees.