The supercell thunderstorm test case.

Steps to run this test case:

1. Link the init_atmosphere_model and atmosphere_model executables from the top-level MPAS directory.

2. Run init_atmosphere_model to create initial conditions.

3. Run atmosphere_model.

4. Run the supercell.ncl script to produce plots theta, vertical velocity, etc.

--------

Revision history:
* NCL plotting script updated on 26 July 2018