Attached below is what I believe is the earliest document in English on an early spectral wave model by Gelci & Chavy (1963), appeared in the conference proceedings on Ocean Wave Spectra by the National Academy of Sciences. The meeting itself was 1961 in Easton, Maryland.
Earlier versions of this paper exist in French, I think as early as 1957 according to some citations. I hope @Fabrice can conjure up something even earlier.
Anyhow, fascinating details in this paper, like the grid setup dependence on the teletype build, hardcoded values of period, direction, and wind speed for table lookup and similar. Only wind input and propagation. Like many papers from this time, things are explained from first principles.
Hi Milan, the group in Casablanca (Morocco) started their operational swell forecasting in 1922, and Sverdrup and Munk (1947) cite their estimation of swell dissipation (a 1937 paper which I have not managed to find yet). Gelci was part of that group and they swtiched to computers at some point in the 1950s. The 1957 paper has unfortunately nothing about numerical methods, and I pretty sure I’ve read another one of their early papers in which they discuss errors caused by lamps burning off (I could have dreamt this but I remember reading this and just cannot find it anymore). I do have the 1918 paper by Gain on which the early method was based. At some point they used observations in the Azores to propagate swells to Morocco.
Gelci finished his career in Brest in the 1980s / 1990s I believe, after transfering to France when Morocco became independent. The DSA models were used at Meteo France until the late 1990s. This was replaced by VAG (a 2nd generation model developed by Anne Guillaume, who was a WAM Group member). VAG was still running in the Mediterranean in the 2000s because of the “limiter bug” in WAM Cycle 4… Jean-Michel Lefevre told me the story that he was not allowed to show the bad results of WAM at a WAM meeting (not sure if Klaus or his boss Anne told him not to show it).
If you look for the early papers, most of what I have in PDF is on this google drive: OTHERS - Google Drive
just search for “Gain” or “Gelci” in there. Google will also find you the papers that cite them (Barnett, Golding …) . I do have a few paper copies and reprints that I should scan one of these days …