[gradsusr] Graphing text file (NOAA aurora forecast) - file format conversion

[Stefan Gofferje (Suomen Sääkeskus)]

Hi,

I'm not really deep in the data formats but maybe somebody here could 
help me out? I'd like to graph the NOAA aurora forecasts with GrADS but 
they offer the data in some custom text file format. The description 
says "Tabular Data is on the following grid: 1024 values covering 0 to 
360 degrees in the horizontal (longitude) direction  (0.32846715 
degrees/value), 512 values covering -90 to 90 degrees in the vertical 
(latitude) direction  (0.3515625 degrees/value), Values range from 0 
(little or no probability of visible aurora) to 100 (high probability of 
visible aurora)".

Here's the file: http://services.swpc.noaa.gov/text/aurora-nowcast-map.txt

Could somebody give me some pointers on how to convert this into a 
gib/grib2 file?

-Stefan