He was part of a Princeton, New Jersey team that in 1950 performed the first successful numerical weather prediction using the ENIAC electronic computer.
[1] In the same year, he was appointed meteorologist at the Norwegian Meteorological Institute, where he came in contact with Arnt Eliassen.
Here, he joined a team composed of the American meteorologists Jule Charney, Philip Thomson, Larry Gates, and applied mathematician John von Neumann, who performed the first successful numerical prediction using the ENIAC electronic computer with the assistance of ENIAC programmer Klara Dan von Neumann.
[7] In 1951, Fjørtoft moved back to Norway, where he took a grand doctorate at the University of Oslo on the stability of atmospheric waves.
[1] Upon leaving the University of Copenhagen in 1955, Fjørtoft was appointed director of the Norwegian Meteorological Institute, where he stayed until 1978.