Here is the non-normalized version, it looks a lot more reasonable now. So any scaling or truncation of the numbers might overly simplify the field lines in the streamplots:

[Stream Plot Laplacian dT/dt non-normalized ](http://files.lossofgenerality.com/daniel_debug_stream2.pdf)

Generally we could have any dimension volumetric data and spline along the axes and take derivatives.