  We present results from the sixth stage of a project to build a statistical
hurricane model. Previous papers have described our modelling of the tracks,
genesis, and lysis of hurricanes. In our track model we have so far employed a
normal distribution for the residuals when computing innovations, even though
we have demonstrated that their distribution is not normal. Here, we test to
see if the track model can be improved by including more realistic non-normal
innovations. The results are mixed. Some features of the model improve, but
others slightly worsen.
