Summary:
- 2+ major hurricanes during ON: 1995, 2001, 2005, 2008, 2016, and 2020
- 1 major hurricane during ON: 1996, 1998, 1999, 2011, and 2017
- 0 major hurricanes during ON: 2000, 2007, 2010, and 2021
The question is: why do some -ENSO seasons fail to take advantage of theoretically favorable conditions?
Some of these can easily be answered: 2007 and 2021 had strong Atlantic Niños, suppressing the ITCZ to the south; and 2000 was a -AMM year. However, some of these make little sense: why did 2010 fail to produce a single major hurricane during ON. It had a -PDO, +AMM, +AMO, and no strong Atlantic Niño; plus, it was ultimately a strong La Niña? What ASO conditions do 2000, 2007, 2010, and 2021 share that the others do not? What ASO conditions do 1996, 1998, 1999, 2011, and 2017 share that the others do not?