2017 Atlantic hurricane season

Collectively, the tropical cyclones were responsible for at least 3,364 deaths. The season also had the highest accumulated cyclone energy (ACE) since 2005 with an approximate index of 224 units, with a record three hurricanes each generating an ACE of over 40: Irma, Jose, and Maria.


This season featured two Category 5 hurricanes (one of only seven on record to feature multiple Category 5 hurricanes), and the only season other than 2007 with two hurricanes making landfall at that intensity. The season's ten hurricanes occurred one after the other, the greatest number of consecutive hurricanes in the satellite era, and tied for the highest number of consecutive hurricanes ever observed in the Atlantic basin.


The season officially began on June 1 and ended on November 30. These dates historically describe the period of year when most tropical cyclones form in the Atlantic basin and are adopted by convention. However, as shown by Tropical Storm Arlene in April, the formation of tropical cyclones was possible at other times of the year. In late August, Hurricane Harvey struck Texas and became the first major hurricane to make landfall in the United States since Wilma in 2005, ending the 12-year US Major Hurricane drought and the strongest since Charley in 2004. The storm tied the record for the costliest tropical cyclone and broke the record for most rainfall dropped by a tropical cyclone in the United States, with extreme flooding in the Houston area. In early September, Hurricane Irma became the first Category 5 hurricane to impact the northern Leeward Islands on record, later making landfall in the Florida Keys as a Category 4 hurricane. In terms of sustained winds, Irma, at the time, became the strongest hurricane ever recorded in the Atlantic basin outside of the Gulf of Mexico and Caribbean, with maximum sustained winds of 180 mph (285 km/h); it was later surpassed in 2019 by Hurricane Dorian. In mid September, Hurricane Maria became the first Category 5 hurricane in history to strike the island of Dominica. It later made landfall in Puerto Rico as a high-end Category 4 hurricane with catastrophic effect. Most of the deaths from this season occurred from Maria. In early October, Hurricane Nate became the fastest-moving tropical cyclone in the Gulf of Mexico on record and the third hurricane to strike the contiguous United States in 2017. Slightly over a week later, Hurricane Ophelia became the easternmost major hurricane in the Atlantic basin on record, and later impacted most of northern Europe as an extratropical cyclone. The season concluded with Tropical Storm Rina, which became extratropical on November 9.


Initial predictions for the season anticipated that an El Niño would develop, lowering tropical cyclone activity. However, the predicted El Niño failed to develop, with cool-neutral conditions developing instead, later progressing to a La Niña—the second one in a row. This led forecasters to raise their predicted totals in late May, with some later anticipating that the season could be the most active since 2010.


Prior to the start of this season, the National Hurricane Center (NHC) changed its policy to permit issuance of advisories on disturbances that were not yet tropical cyclones but had a high chance to become one, and were expected to bring tropical storm or hurricane conditions to landmasses within 48 hours. As a result of this change, early watches and warnings could be issued by local authorities. Such systems would be termed "potential tropical cyclones".^[2] The first storm to receive this designation was Potential Tropical Cyclone Two, which later developed into Tropical Storm Bret, east-southeast of the Windward Islands on June 18.^[3] Additionally, the number assigned to a potential tropical cyclone would remain with that disturbance, meaning that the next identified tropical system would be designated with the following number, even if the potential tropical cyclone did not develop into one. The first such system was Potential Tropical Cyclone Ten in August.