BUG: logical operations in winds.py

I thought I was handling both np.ndarray and np.ma.core.MaskedArray
cases appropriately, but I discovered certain cases where the code would
fail. I believe an easy remedy (which I have made) is to use
np.ma.filled() on all data arrays and strictly deal with the np.ndarray
case. Note that np.ma.filled() produces desirable results whether it is
passed a np.ndarray or a np.ma.core.MaskedArray.