The 2015 Northern Hemisphere tropical cyclone (TC) in 2015 stands as the most active season for intense tropical cyclones on record, by a large margin.
The extraordinarily busy year is most directly linked to the strong El Niño event in the tropical Pacific Ocean, which has infused unusually warm water in many parts of that basin, fueling intense storm after intense storm.
Recall that when we refer to tropical cyclones, they encompass hurricanes, typhoons, and cyclones – which are all the same breed of storm, but called different things in different parts in the world.
Let’s take a holistic and then basin by basin look at 2015’s tropical cyclone numbers in the Northern Hemisphere.
Northern Hemisphere summary
Adding together the storms across all ocean basins, the number of intense tropical cyclones to form in the Northern Hemisphere in 2015 is unprecedented in modern records. 27 major tropical cyclones (winds greater than or equal to 111 mph) have occurred this year which is four more than any other year.
Year-to-date, Accumulated Cyclone Energy, a metric that measures overall hurricane season levels through a combination of frequency, intensity and duration, is at record high levels.
While Northern Hemisphere TC activity has calmed down recently, there is certainly the potential that more damaging TCs could form prior to the end of the year.
The Northeast Pacific has been quite active, with ACE to date trailing only 1992.
The level of activity in the North Central Pacific (180-140 degrees west) portion of the basin stands out as most notable. More named storms, hurricanes and major hurricanes have existed in this region than any year on record (reliable data exists for the North Central Pacific since around 1980).
The most memorable storm of the 2015 season in the Northeast Pacific is Hurricane Patricia, which had maximum sustained winds of 200 miles per hour and a minimum surface pressure of 879 mb, both records for the Western Hemisphere. Fortunately, Patricia made landfall in a relatively undeveloped portion of Mexico which drastically reduced both damage and fatalities from what otherwise would likely have occurred.
The table below summarizes tropical cyclone activity to date using four different measures: named storms (winds greater than or equal to 39 mph), hurricanes (winds greater than or equal to 74 mph, major hurricanes (winds greater than or equal to 111 miles per hour) and ACE.
The Northwest Pacific has also been very active, with ACE only trailing the incredibly strong El Niño year of 1997. The season has witnessed a large number of Cat. 3+ typhoons (winds greater than or equal 111 mph), with 14 experienced so far this year, tying 1965 for the most ever observed in the Northwest Pacific to date. (Note that hurricanes are called typhoons in the Northwest Pacific.)
Typhoon Soudelor was the strongest typhoon of the Northwest Pacific season, with maximum sustained winds estimated at 180 miles per hour. Saipan, Taiwan and portions of eastern China were devastated by the typhoon, with at least 38 fatalities attributed to the system. Damage is estimated at over $3 billion US dollars.
El Niño typically reduces Atlantic storm activity through increases in upper-level winds that tear apart hurricanes as they are trying to form. 2015 has been no exception, with overall activity only about 60 percent of normal to date.
The most notable Atlantic storm has been Hurricane Joaquin which devastated portions of the Bahamas. It was also the first Category 4 hurricane to impact the Bahamas during October since 1866.
North Indian Ocean
The North Indian Ocean had been fairly quiet until Cyclone Chapala formed last week. Chapala became the second strongest TC in the Arabian Sea on record with maximum winds estimated at 155 mph, trailing only Gonu (2007) which had winds of 160 mph. Chapala was also the longest-lived Cat. 3+ cyclone in the North Indian Ocean on record. Note that all TCs, regardless of strength, are called cyclones in the North Indian Ocean.
Chapala made landfall in Yemen early on November 3, becoming the first named TC to strike Yemen since 1960. It is likely also the first cyclone with hurricane-force winds to strike Yemen since the modern era began in the 1940s.