Predictability of the 2017 North Atlantic hurricane season

• Published in: Atmospheric Science Letters
• Main Authors: Camp, Joanne, Scaife, Adam A., Heming, Julian
• Other Authors: DECC/Defra Met Office Hadley Centre Climate Program, UK Public Weather Service
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: North Atlantic
• Online Access: http://dx.doi.org/10.1002/asl.813; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fasl.813; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/asl.813

The 2017 North Atlantic hurricane season was one of the most active in recent history. The season recorded a total of 17 named storms, of which 10 became hurricanes and 6 became major hurricanes, and an Accumulated Cyclone Energy (ACE) index of 226. The number of major hurricanes was joint second highest since 1970, and the ACE index was third highest. We show that the Met Office Atlantic seasonal tropical cyclone forecast, initialised on May 15, 2017, predicted an increased risk of above‐average activity. The forecast also captured aspects of the spatial distribution of the tropical cyclones, such as the high frequency of tracks which crossed the northeast Caribbean in September 2017, at more than 3 months lead time. We show that the high levels of seasonal activity, particularly in terms of major hurricanes and ACE index, were likely a result of a combination of low wind shear in the western Atlantic, above‐average tropical Atlantic sea surface temperatures (SSTs) and a transition to cooler SSTs in the tropical Pacific due to a developing La Niña event, all of which appear to be predictable at seasonal lead times. This study provides evidence for seasonal predictability of the intense 2017 Atlantic hurricane season, including advanced warning of an increased risk of tropical cyclones transiting the northeast Caribbean.