How and when rogue waves form is still unknown and being discovered by scientists. A few of their causes, however, are thought to include constructive interference and focusing of wave energy.
Scientists have studied constructive interference and its effect on rogue waves. When swells traveling across the ocean at different speeds and directions pass each other, they sometimes collide. This causes their crests, troughs and lengths to reinforce each other, creating towering waves that disperse quickly. However, if these swells are traveling in the same direction, these giant waves can last for a few minutes.
Another cause of rogue waves is the focusing of wave energy. Storms create waves that go against the normal wave direction, shortening the wave frequency. This can cause waves to join up and create larger waves. Both of these are possible explanations for how rogue waves are caused. Rogue waves are monstrous, steep waves that appear out of nowhere. As rare as they are, sailors who have seen rogue waves describe them as a giant wall of water. Rogue waves are unpredictable and come opposite of the prevailing winds and waves.There is not a set height that classifies a rogue waves as such. Instead, it is distinguished as being at least twice as large as surrounding waves.