money quote:
"First, is that typically La Niña follows El Niño, but this is an example of a La Niña event that had no preceding El Niño. That’s not completely impossible, but unlikely. The second thing is, we had this La Niña event that lasted for three years that didn’t follow an El Niño. That is unprecedented. Previous long-lasting La Niñas have always happened after a strong El Niño.”