One of the early customers was the European Centre for Medium-Range Weather Forecasts, so, wild guess, they probably used it for medium-range weather forecasts.
in europe
( There was a seperate dedicated weather computer, this one was used for 'other' jobs like speculative weather modelling, monster group algebraic fun, et al.)
https://en.wikipedia.org/wiki/CDC_Cyber
The UK was the first customer:
In 1980, the successor to the Cyber 203, the Cyber 205 was announced. The UK Meteorological Office at Bracknell, England was the first customer and they received their Cyber 205 in 1981.If you really want a challenge, do it using pen, paper and a slide rule, like in the old days[1]. Just make sure to apply appropriate smoothing of the input data first[2].
[1]: https://www.smithsonianmag.com/history/how-world-war-i-chang...