Still need to implement. 

Will need to download data:

  wget https://storage.googleapis.com/track_data_ncar_ams_3km_nc_small/track_data_ncar_ams_3km_nc_small.tar.gz
  tar -xvzf track_data_ncar_ams_3km_nc_small.tar.gz


Then calc cov matrix

  python utils/get_tornado.py \
    -n data/track_data_ncar_ams_3km_nc_small/NCARSTORM_20170323-0000_d01_model_patches.nc,data/track_data_ncar_ams_3km_nc_small/NCARSTORM_20170329-0000_d01_model_patches.nc # Comma-delimited storm patch files
    -o out/tornado_cov.npz 
