No surprises with the late call of La Nina here in this country, we have been talking about this developing since Winter 2021. The event has been underway since October generally and now strengthening.
What do you need to know though?
Well the BoM is following a policy line of following their ACCESS model which is calling for a weak La Nina (this same model also sits well outside of the more reputable international models which deepen and prolong the ENSO phase). That would mean that the event would not have the same implications as last year, however last year the model played catch up looking at my records.
Cast your mind back to last year and when La Nina was declared. Many were asking where is La Nina? Where is the rain? Well there are no questions about that this year thanks to the negative IOD, but also influencing the weather is the La Nina. It is earlier this year, the waters east of Australia are suggesting that and the atmosphere is responding.
Where we had elevated moisture levels and rainfall events post Christmas 2020r, this year it appears that the impacts are being felt pre Christmas 2021. The concerning element in that is we may see a protracted period of this type of weather which does not get even spoken about. I do not know why, when the impacts are just as problematic and disruptive for many who rely on that information.
International Model Predictions of ENSO for the next 9 months.
Only one model which is the BCC takes us into an El Nino. The reputable NOAA strengthens the La Nina to an event not seen since the 1970s and has not budged from this, other models in the plot support a much stronger and prolonged La Nina that the BoM model. Follow the Green, Blue and Red Lines as they are the model averages and taking those at face value, we are staring down a stronger event than last season. The event may persist deep into Autumn with the CPC suggesting this may be the case with a 70% chance of this occurring. Remember this product has been screaming La Nina since August as I have. Now it is a matter of how strong and how long.
BoM ENSO Outlook November 23rd 2021
The ACCESS model which is traditionally not the highest scoring model out of the suite is conservative and rather erratic in the approach to this unfolding ENSO phase with a rapid drop in the coming 4 weeks, plateauing and then resuming a neutral phase. I give this a very LOW chance of verifying.
Euro - Nino 3.4 Anomaly - November Plume.
Can see that even the Euro is becoming more aggressive on the La Nina event, after being more conservative, it has started to follow the NOAA forecast and deepening the phase before it wanes in the early Autumn. This La Nina phase could be with us for 3-4 months which would be very problematic where as the BoM says its done by early Feb. That extra 6 weeks could be a huge issue for those forward planning.
Euro Rainfall Outlook - Summer
The wet bias is over northern and eastern Australia. The heightened rainfall chances for QLD and NSW is the further east you go. Seasonal conditions elsewhere with a leaning above normal for many states. The wet season productive.
Euro Rainfall Outlook - Autumn
The chances of an early Autumn break look high for 2022. And the season overall looks wetter than normal for northern and central Australia which may be connected to the lingering wet season/cyclone season and the La Nina lingering longer would result in more green being painted on this chart for eastern areas of the nation.
The take away is.
La Nina is here, but how long is she here for? That question will be likely answered in December when the fresh plume data is available.
Have we seen the peak of the wet weather? NO! What we are experiencing now is from the negative IOD which was not spoken about by many agencies. You don't need to have a major event to have major impacts if everything comes together as we have seen.
Not one event is ever the same, this event has a nasty feel to it for northern and eastern Australia with high end flooding for many locations for a prolonged period.