While El Niño forms across the tropical Pacific, forecasters look at one region in particular called the Niño3.4, monitoring a three-monthly average of the sea surface temperature compared to the long-term average.
A strong or ‘super El Nińo’ is when that goes above 1.5C.
Forecasts from the European Centre for Medium Range Weather Forecasts (EC), NOAA and BoM are all pretty much aligned in their outcomes.
In the latest prediction from the EC, more than half of their forecast models suggest a temperature of over 2.5C by the autumn.
Anything over 2.5C would be a “historically strong event,” said Johnson.
BoM forecasts are also confidently showing the possibility of a very strong El Niño to develop later this year.
Some forecast data is even suggesting the temperature could exceed 3C, surpassing the current known peak of 2.7C recorded in 1877.
It should be noted this was a very different era with limited observations and so there remains a lot of uncertainty in the reported temperature.
That El Niño lasted around 18 months which triggered a catastrophic global climate event, causing extreme drought and widespread famine across Asia, Brazil, and Africa which killed millions, while producing severe flooding in other regions like Peru.
The last ‘very strong’ El Niño occured in 2015-2016 when the average three-monthly (November, December, January) Niño3.4 temperature reached 2.4C.