Looks like one may be forming right now.
Judith, the question that needs answering: Are weather conditions right for a series of westerly wind bursts in the western tropical Pacific? Without westerly wind bursts to initiate downwelling Kelvin waves, there will be no El Niño.
So this morning I checked with the NOAA GODAS website, and, yes, there have been westerly wind bursts this year. See the hovmoller plot of the “Surface zonal wind stress anomaly” from the GODAS Pentad Anomaly Products webpage (my Figure 1 below).
Then it was time to check the subsurface temperature anomalies for the equatorial Pacific. And they can be found at the NOAA CDC webpage here. See animation 1 below. A downwelling Kelvin wave is already making its way across the equatorial Pacific.
So to answer the title question, it obviously appears the initial phases of the processes that initiate an El Niño are already in progress.
Will an El Niño in 2018/19 be strong enough to permanently raise global sea surface temperatures?
Only time will tell. And if you’re wondering how a strong El Niño can (and does) raise global sea surface temperatures permanently, then you obviously haven’t read my ebook Dad, Why Are You A Global Warming Denier? – A Short Story That’s Right for the Times, which is available in Kindle ebook and in paperback editions. In that book, I’ve explained how a strong El Niño can (and does) raise global sea surface temperatures permanently so simply that an eight-year-old can understand it. How do I know? In real life, I explained it to an eight year old, and he understood, no problem. BTW, I have not discussed, and have no intention of discussing, that very simple aspect of strong El Niños in a blog post.