Thursday, December 29, 2016

2016 Season Summary

The 2016 Atlantic hurricane season had below-average activity, with a total of

16 cyclones attaining tropical depression status,
15 cyclones attaining tropical storm status,
7 cyclones attaining hurricane status, and
3 cyclones attaining major hurricane status.

Before the beginning of the season, I predicted that there would be

14 cyclones attaining tropical depression status,
13 cyclones attaining tropical storm status,
7 cyclones attaining hurricane status, and
3 cyclones attaining major hurricane status.

The season was just a bit above average, since the average numbers of tropical storms, hurricanes, and major hurricanes are 12.1, 6.4, and 2.7, respectively. My predictions at the beginning of the season were close to the actual result, with the only difference being in the number of tropical depressions and tropical storms. The Accumulated Cyclone Energy of the 2016 season was 132, an above average value, since there were a few relatively long-lived and intense hurricanes. In particular, Hurricane Matthew had an individual ACE of about 48, the highest for a single Atlantic hurricane in a dozen years.

The biggest story in 2015 for Atlantic hurricane development was the 2014-5 strong El Nino event. Indicated by anomalously warm ocean temperatures over the equatorial East Pacific region, this event limited the 2015 season to below-average activity. However, by the end of that year, it was diminishing, and fairly neutral conditions prevailed throughout the 2016 hurricane season. Generally speaking, El Nino inhibits tropical cyclone formation and La Nina conditions (with anomalously cool ocean temperatures over the same Pacific region) support it. The near-average 2016 season was consistent with this general rule.

Atlantic ocean temperatures were also not quite as extremely warm as in 2015, but more favorable atmospheric conditions in the Caribbean Sea and Gulf of Mexico allowed systems to form in areas likely to result in landfalls. Hurricane Matthew was by far the most notable hurricane of the season, strengthening into a category 5 in the Caribbean at an unprecedentedly low latitude. It was also the first category 5 in the basin since 2007. The system went on to devastate Haiti with a category 4 landfall, and later affected Cuba, the Bahamas, and the southeastern United States. Some other notable facts and statistics concerning this season include:
  • Hurricane Alex formed in January, making it the first hurricane to form in the month since 1938
  • Following the rapid start to the season with Alex and Bonnie, Tropical Storm Colin and Tropical Storm Danielle became the earliest forming 3rd and 4th tropical storms in an Atlantic season in recorded history
  • Tropical Storm Julia actually formed with its center of circulation over land, marking the first occurrence of this phenomenon since 1988
  • When Hurricane Nicole achieved category 4 status, 2016 became the first known season to have two category 4 hurricanes (the other was Matthew) exist in the month of October
  • The season ended on another unusual note, with Hurricane Otto becoming the southernmost landfalling hurricane in Central America ever recorded, and the first Atlantic storm to cross into the East Pacific basin since 1996
  • Unfortunately, the death toll of the 2016 season exceeded 1700 people (with most of these occurring in Haiti due to Hurricane Matthew), making 2016 the deadliest Atlantic hurricane season since 2005

The 2016 season was not extraordinarily active, but saw a relatively high number of landfalling systems in the Caribbean, the Gulf, and elsewhere.