June 1 marked the official start of the Atlantic hurricane season, which runs through the end of November. It’s a busy time for us at the Tropical Meteorology Project in Colorado State University’s (CSU) Department of Atmospheric Science, where we are issuing our 34th annual Atlantic basin seasonal hurricane forecast.

In early April we predicted a slightly below-normal hurricane season for 2017, with a total of 11 named storms (average is 12), four hurricanes (average is six) and two major hurricanes (average is two). To be named, a tropical cyclone must have maximum one-minute sustained winds of 39 mph. If it strengthens to 74 mph, it is called a hurricane, and if the winds reach 111 mph, it is called a major hurricane.

Here’s a look at how we develop our forecasts.

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