Current forecasts of Eastern Pacific sea surface temperatures (SST) and expert judgement point to a significant likelihood of an El Nino materializing: currently this stands at over 90% chance of it happening by early 2019.
How long is it likely to last and how intense is it likely to get?
Judging from the forecasts for how SST are likely to evolve, this El Nino, should it materialize, is likely to be relatively short and over by mid 2019. Based on the same evidence, and other features of the Pacific ocean circulation, it is likely to remain a weak to moderate El Nino, much weaker than the 2014-16 event.
Is it possible it won’t happen at all?
This remains a possibility. So far, although the Pacific Sea Surface Temperature patterns are in place, these have not yet “connected” properly to the atmosphere and the circulation patterns typical of El Ninos have not picked up enough for an El Nino to be declared.
If an El Nino is not declared, does it mean its impacts will not happen?
No. El Nino events are not on-off phenomena. An El Nino declaration is made based on a number of ocean and atmospheric features being in place. Even if these are not fully met and no El Nino is declared, you will be very close to it and therefore some areas of the globe may well experience impacts typical of “official” El Ninos.
We see this being played out in Southern Africa (typical El Nino-like situation), Indonesia (El Nino-lite features) and East Africa (outcomes opposite to typical El Nino). See ahead for details.