Well, if by weather we consider the broader meterological picture (atmosphere, climate, seasonal changes) then the arctic conditions that ultimately form an iceberg, and that it was the season for ice in the North Atlantic, would technically qualify it as "weather."
That said, I'm not sure I would have thought of the climate and weather of 1912 a big enough deal in 2007 to rank it on a top 100 list (1912 is hardly the only year there have been icebergs).
However, it's not every year an iceberg sinks a ship, kills hundreds of people, and changes the course of history. And for weather-related, we now ended up with the International Ice Patrol. So all that might justify ranking it as a "Weather Moment".