The Bureau of Meteorology issued its Climate Driver Update yesterday. While that may not mean much to many readers, it will when I say that the chances of a La Niña returning to the Northern Rivers in 2024/25 is 50/50, and if it does, it will be weak.

La Niña is the cool phase of the El Niño Southern Oscillation (ENSO). It is associated with cooler-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean.

(an image reflecting a La Niña weather pattern. Source: BoM)

Recent observations and model forecasts show the central tropical Pacific Ocean is now 0.8°C cooler than normal, and that has resulted in changes to Trade Winds and pressure patterns.

The Bureau's model suggests sea surface temperatures (SST) are likely to remain within the ENSO (El Niño-Southern Oscillation-neutral range (-0.8 °C to 0.8 °C) throughout the forecast to February 2025.

Of the six other climate models surveyed, three suggest SSTs in the tropical Pacific are likely to exceed the La Niña threshold (below -0.8 °C) from this month. In comparison, another three models forecast SSTs to fall just short of the threshold from November.

The prediction is that if a La Niña does develop in the coming months, it is forecast to be relatively weak (in terms of the strength of the SST anomaly) and short-lived, with all models indicating a return to neutral by February.

Of course, a neutral weather system or a weak La Niña doesn't mean we will not experience a wet rest of spring and summer.

In terms of the next three months (October to December), The Bureau has forecast a slightly wetter and slightly warmer period.

The chance of above-median rainfall, which is greater than 311mm, is 66%, and the chance of an unusually wet three months (greater than 386.5mm) is 31%.

To give that some perspective, in 2023, the recorded rainfall for the same period was 308.4mm.

We have already experienced some very hot days at the end of winter, indicating that summer will be warmer than last year.

The Bureau says there is a 75% chance of above-median temperatures, which is greater than 27°C, and a 26% chance of an unusually warm October to December period (greater than 28.1°C).

In 2023, the mean for each month was:

• October - 27.7°C
• November - 26.9°C
• December - 31.7°C

The hottest days in each month were:

• October - 36.7°C
• November - 35.5°C
• December - 37°C

So, it looks like more of the same or slightly warmer days are on the way in the next three months.

As for the immediate weather situation heading into the first long weekend since early June, the clouds will dissipate, and the sun will come out, leaving us with blue skies and temperatures in the late 20s and early 30s.

After the conditions we have had in the last week, we'll take it.