Question

How large a wave would be generated from a 50 mph wind, with a 1420 mile fetch, over a 69 hour period be?

Answer 1

Beaufort force 9 severe gale.  After 8-10 hours of constant force the average height would be about 7 meters.

Answer 2

In your question where the ask is how large a wave would be generated if 50mph of wind, with 1420 mile fetch, over  69 hours period of time and base on my calculation and analyzation and also in deep understanding about this problem I came up with an answer of 97 and its D.