[m_mueller]

Fortran and Python go together very well (they complement each other in just the right ways and there's all the bindings / data structure compatibility with Numpy that you need). Glue code / UI in Python, Numerics in Numpy + homegrown Fortran, that's how I'd implement a numerical model from scratch today.

[septc]

Just out of curiosity, what do you use for calling Fortran from Python (e.g. f2py, ctypes)? Do you have any suggestion about how to combine them together (e.g., for parallel calculations)?

[m_mueller]

So I haven't yet had the chance to do it myself, but yes I'd look at f2py first and how to integrate it with Numpy.