Weekly OISST.v2 dataset goes back to 1990. Since then, there have been 8 onset El Niño years (can't be a second year Niño, e.g. 2015). I plotted their mean weekly 3.4 anom and max/min range by week for all 52 weeks. I'll regularly update this. pic.twitter.com/ImHNdSUuGL

— Anthony Masiello (@antmasiello) April 19, 2018