The 2013 Atlantic Hurricane Season was a relatively quiet season, in contrast to the two previous seasons. There were 13 tropical storms, which is a fairly high number, but of these, only two developed into hurricanes, neither of which got above category 1. Having only two hurricanes means this is one of the only two times since 1950 when there were only two hurricanes in a season. And this is one of only five times since 1950 when there were no major hurricanes in a season.
This is a rather unusual season to figure out. The number of tropical storms, 13, is still a relatively high number of storms, and yet the number of hurricanes and major hurricanes was very low. The pattern in which the storms was distributed was also unusual: there were two storms in June, which is a high number, and only four in September, which is a low number. To have a large number of tropical storms, spread throughout the season, with the peak of the season being so ill-defined, is an unusual pattern. Also, despite the quiet year in the Atlantic, it was a busy season in the Eastern Pacific, with 18 storms and 9 hurricanes. And in what was reputedly one of the most powerful hurricanes ever recorded, Super Typhoon Haiyan, hit The Philippines.
It is unclear what any of this means. The Atlantic has been busy for the past decade, and the three guesses about why this is are:
- Periodic oscillation in climate conditions, such as El Nino
- A long term trend due to climate change
- An artifact of better monitoring: satellite monitoring of the Atlantic might be turning up short-lived tropical storms that would have once gone unnoticed
All of these guesses make sense, and all of them leave some questions. But this year's season, an underpowered season with an unusual profile, especially with such a busy season in the Pacific, makes the question that much more difficult.