When SAIL decided to print something on rogue waves (October, 2003), the first question that came up among the editors was—what IS a rogue wave? Soon it became clear that "rogue wave" means different things to different people. Faced with the job of making sense, or a bit of sense, of the jumble, I eventually decided that a rogue is any wave that is bigger, steeper, moving faster, or coming from an angle different from whatever the boat and crew were prepared for. In storm conditions, a rogue can rise out of a wave train in which one wave overtakes another, and multiple waves build combined energy and height. Big waves are frightening, but not necessarily dangerous unless they're breaking. Cross-pattern seas can be the most dangerous to meet.
Additive rogue waves are statically predictable (so you could argue they are not "rogues" at all, but that's not a productive line of argument). Cross-pattern rogues should have a level of predictability if you are able to know what's happening in other parts of the ocean, but for most of us most of the time that's a lot to ask. The great puzzles are the documented rogue waves that seem to appear out of nowhere and nothing on a mild day in a mild sea (not to be confused with tsunamis, which have little effect on open water).
There's quite a bit of information online. Look below the Sponsored Links for a sampling that I found informative, entertaining, or both—Kimball Livingston
Heavy scientific noodling from NOAA: NOAA on rogue waves
A window into the world of the scientists who study rogue waves for a living, largely on behalf of international shipping and oil platform companies: Scientific conferences and Modeling a rogue wave; is it possible?
The brief text here is actually about the camera used to make the shot, but it's worth a click to see the shot: big ship in BIG wave
A BBC news story analyzing the sinking of a ship by waves that were deadly because they were the same length as the ship: BBC on sinkings
A student expedition to a wave-beaten peninsula proves that the umpteenth wave can be much bigger than the ones before Almost scary
An account of the QEII's encounter with something real, real big: QEII's storm encounter
And an account of the 61-foot Sorcery's encounter with "A freight train: There was no time to react. As the starboard locker emptied onto me, the engine, which had been battery charging, kicked off. I piledrived into the amazingly white surface of the overhead, right where the cabin sole used to be; the port lockers emptied out. Sometime in between, it seemed that a wave had washed through into the forepeak, but I barely noticed it. Everything was very, very vague, and I sat buried in cans and boxes on the cabin sole watching black stuff run down my arms. The whole world kept going in a barrel roll, and the noise was like being in a cement mixer. The first definite sounds that penetrated the chaos were piercing screams from on deck, then a sound of "Man Overboard, Man Overboard, Man Overboard". One yacht's trial
Info about the Coastal Data Information Program (CDIP), which measures, analyzes, archives, and disseminates coastal environment data for use by coastal engineers, planners, and managers as well as scientists and mariners. A West Coast deal at CDIP
The quote is a fair taste of what you will find here: "Writing in Smithsonian Magazine, Peter Britton cites a study of giant waves in the Gulf of Alaska. Waves there are found to be no worse than in the northern North Sea, where extreme wave heights are near 100 feet. However, the study indicates that the maximum possible wave height in the Gulf of Alaska is a terrifying 198 feet:" Alaska Science Forum
Here's the Marine Prediction Center on its part in predicting "The Perfect Storm:" NOAA tracks a big one