2016 North Atlantic Hurricane Season Review RMS REPORT 1 Executive Summary The 2016 North Atlantic hurricane season will be remembered for several reasons. First and foremost, Major Hurricane Matthew, the first Category 5 storm in the Atlantic Basin since 2007, impacted the Caribbean and southeastern United States in early October. Although the U.S. was spared major wind damage from Hurricane Matthew, high winds and flooding, driven by storm surge and rainfall, impacted coastal areas from central Florida to North Carolina. Florida saw the first hurricane landfall in 11 years when Hurricane Hermine made landfall in the Big Bend region of Florida in September, followed in early October by a near miss from Major Hurricane Matthew, which came within 5 mi (8 km) of landfall as it tracked up the east coast of the state. With Matthew’s miss, the well- publicized “hurricane drought,” a term given to the lack of major hurricane landfalls in the U.S., was extended to an 11th season. Hurricane activity got off to an early start when Hurricane Alex spun up in mid-January, becoming the second earliest hurricane on record. In addition, the season ended late, as Hurricane Otto made landfall in Nicaragua in late November. The gap between the two events – at 318 days – broke the record for the most number of days between the first storm forming and the last storm dissipating. The rest of the hurricane season lived up to forecasters’ expectations with slightly above-average named storm activity, near-average hurricane and slightly above-average major hurricane activity, closing with fifteen named storms, seven hurricanes, and four major hurricanes. Early 2017 hurricane season forecasts by Tropical Storm Risk (TSR) predict the 2017 season will be similar to 2016, although forecast skill at this lead time is poor. Colorado State University (CSU) anticipates that activity in the 2017 season will be determined by the strength of the thermohaline circulation (THC) and Atlantic Multidecadal Oscillation (AMO), as well as the phase of El Niño-Southern Oscillation (ENSO). 1 Overview of the 2016 North Atlantic Hurricane Season The 2016 season was the most active since 2012. Fifteen named storms formed in 2016, which was above the 1950-2015 average1 (11.2 storms) and slightly above the 1995-2015 average2 (14.6 storms), as seen in Figure 1. Seven hurricanes formed in 2016, slightly above the 1950-2015 average (6.2 storms) but slightly below the 1995- 2015 average (7.4 storms). There were four major hurricanes (Category 3 and above) during the 2016 season,3 which lies above the average for 1950-2015 (2.7 storms) and 1995-2015 (3.4 storms). 1950-2015 Average 1995-2015 Average 2016 Season 16 15.0 14 14.6 12 11.2 10 8 7.4 7.0 Number of Storms of Number 6 6.2 4 4.0 3.4 2 2.7 0 Named Storms Hurricanes Major Hurricanes Figure 1: Comparison of the 2016 North Atlantic hurricane season storms to the 1950-2015 and 1995-2015 averages. (Data from the National Oceanic and Atmospheric Administration Hurricane Research Division, 2017.) A total of five storms made landfall in the United States in 2016 – three tropical storms (Bonnie, Colin, and Julia) and two hurricanes (Hermine and Matthew) – though no major hurricanes made landfall. The 2016 season extended the longest period without a major hurricane landfall in the U.S. to 11 years, since records began in 1851. The last major hurricane to make landfall in the U.S. was Hurricane Wilma in 2005. Prior to the 2016 season, Wilma was also Florida’s last hurricane landfall of any intensity. Hurricane Hermine broke this streak, making landfall in the Big Bend region of Florida on September 2 as a Category 1 hurricane. Major Hurricane Matthew was the strongest storm of the 2016 season, reaching peak intensity as a Category 5 hurricane in the Caribbean Sea. Matthew later made landfall over Haiti and Cuba as a strong Category 4 storm before weakening slightly and tracking through the Bahamas as a Category 3 storm. Matthew tracked offshore along Florida’s east coast as a Category 3 storm and briefly made landfall as a Category 1 storm in South Carolina. 1The historical database for land falling hurricanes worldwide is generally agreed to be complete since 1990. However, the record of hurricane activity in the Atlantic Basin alone is generally agreed to be complete only from 1950 onward, following the increases in aircraft reconnaissance and the onset of satellite technology. 2It is widely recognized that the Atlantic Basin entered a period of elevated activity in 1995 compared to the long-term historical average, driven by a positive phase in the Atlantic Multidecadal Oscillation. 3In its post-season assessment released on January 30, 2017, the National Hurricane Center (NHC) increased the intensity of Hurricane Otto to Category 3, making it the fourth major hurricane of the 2016 season. 2 The Accumulated Cyclone Energy (ACE) index,4 which provides an alternative assessment of hurricane activity based on intensity and duration, was above both the long-term (1950-2015) and recent (1995-2015) averages at 138.31 (104 kt2) in 2016. The 2016 season ACE index ranks as the largest since 2010 at 38 percent above the long-term average of 100.4 and 10 percent above the recent average of 125.5, as illustrated in Figure 2. Major Hurricane Matthew contributed approximately 35 percent of the total 2016 ACE index, breaking the record for the most ACE generated by a hurricane in the eastern Caribbean Sea,5 and is ranked as eighth highest among Atlantic hurricanes in the satellite era. Figure 3 shows ACE value for all storms in the 2016 season. 250 200 ) 150 2 kt 2016 ACE 4 1995-2015 Average ACE (10 1950-2015 100 Average 50 0 1950 1960 1970 1980 1990 2000 2010 Figure 2: North Atlantic hurricane season Accumulated Cyclone Energy (ACE) totals and 1950-2015 and 1995-2015 averages. (Data from WeatherBell Models, 2016.) [WeatherBell Models ACE values represent the operational advisories and not the post-season reports published by the National Hurricane Center and therefore these ACE values do not show the retrospective upgrade of Hurricane Otto] 60 50 ) 2 40 kt 4 30 ACE (10 20 10 0 Figure 3: Accumulated Cyclone Energy (ACE) values for storms in the 2016 season (TD = Tropical Depression, TS = Tropical Storm, H = Hurricane, MH = Major Hurricane). (Data from WeatherBell Models, 2016.) [WeatherBell Models ACE values represent the operational advisories and not the post-season reports published by the National Hurricane Center and therefore these ACE values do not show the retrospective upgrade of Hurricane Otto] 4ACE is calculated as the square of the sum of the maximum sustained wind speed (in knots) at 6-hour intervals for the duration of the storm at tropical storm status or greater (sustained wind speeds of 35 knots or higher). The unit of ACE is 104 kt2 5Matthew broke the record of Hurricane David (1979). 3 The 2016 North Atlantic Storms and Their Impacts The 2016 North Atlantic hurricane season broke the record for the most number of days – 318 – between the first storm forming and the last storm dissipating. The period lasted from January 12 when Hurricane Alex formed to November 26 when Hurricane Otto dissipated, beating the previous record of 311 days set in 1938. The 2016 season was particularly active in terms of land falling storms – 10 of the 15 named storms made landfall, while a further two tracked close enough to impact land. Five storms made landfall in the U.S.: Tropical Storm Bonnie, Tropical Storm Colin, Tropical Storm Julia, Hurricane Hermine, and Hurricane Matthew. Three storms made landfall over Mexico and Central America: Tropical Storm Danielle (Mexico), Hurricane Earl (Belize), and Major Hurricane Otto (Nicaragua). Major Hurricane Matthew impacted the Caribbean, with landfalls in Haiti, Cuba, and the Bahamas. Meanwhile Major Hurricane Nicole made landfall over Bermuda as a Category 2 storm and Hurricane Alex made landfall in the Azores. The 2016 North Atlantic storm activity is illustrated in Figures 4 and 5. Figure 4: The 2016 North Atlantic storm tracks and intensities. (Data from the National Hurricane Center, 2017.) 4 2.25 Named Storm January May June July August September October November H Alex 3.6 TS Bonnie 1.1 TS Colin 1.7 TS Danielle 0.4 H Earl 4.1 TS Fiona 2.7 MH Gaston 24.6 TD Eight 0.0 H Hermine 3.5 TS Ian 3.5 TS Julia 1.6 TS Karl 7.0 TS Lisa 3.1 MH Matthew 48.5 MH Nicole 25.7 H Otto 6.6 Figure 5: Timeline of the 2016 North Atlantic hurricane season (TD = Tropical Depression, TS = Tropical Storm, H = Hurricane, MH = Major Hurricane) with Accumulated Cyclone Energy (ACE) values for each storm. (Data for timeline from the National Hurricane Center, 2016; data for ACE values from WeatherBell Models, 2016.) [WeatherBell Models ACE values represent the operational advisories and not the post-season reports published by the National Hurricane Center and therefore these ACE values do not show the retrospective upgrade of Hurricane Otto] Hurricane Alex The first named storm of the 2016 season, Hurricane Alex, formed in the eastern North Atlantic on January 13, becoming the second earliest hurricane on record6 and just the fourth named Atlantic storm to form in January since records began in 1851. Alex is also only the second hurricane to form in the Atlantic Basin east of 30°W and north of 30°N after Vince in 2005. Alex tracked north into increasingly cooler sea surface temperatures and weakened before making landfall on the island of Terceira on January 15 as a tropical storm, with maximum sustained wind speeds of 63 mph (101 km/hr).