LA NINA UPDATE - HOW LONG WILL SHE LAST?

I touched on this during Friday but wanted to expand some thoughts on the position of the La Nina and to broaden the perspective from not just being what the Australian agencies are saying, but what about the more trusted international agencies, which have been forecasting this La Nina since last August....and here we are.


How long does it last? How strong does it get? Do we see it resolve by Autumn or linger closer to Winter? Are we set for another La Nina in the Spring and Summer of this year?


Lets try and answer some of these questions.


ENSO PREDICTIONS 2022

You can see some of the members from some fairly reputable climate agencies are suggesting that the La Nina will linger well on into our Autumn and not quite resolve out of the cool neutral. Some of the members to resolve it back to neutral but not placing very deep into positive territory, setting us up for possibly another La Nina phase as we track into our Spring and Summer. Now the February and March plumes that are delivered are usually low confidence, but reviewing the data from last year this time, they did have us remaining in neutral territory, with some forecasters saying they would "eat their hat" if there was a La Nina with this service the only one calling a La Nina alert back in July of last year to the raucous laughter. So it pays to not just read one set of data but look at conditions as we go along through the Autumn. Does the La Nina linger onwards? If it does, that means the recovery to neutral may be held back meaning the door is left open for more cooling into Spring and Summer later this year in the region.

This is one of the climate models and it suggests it does not come out of La Nina conditions all year, which would be unprecedented, the thing that I want you to notice is not only the black line which is the line you should use, but how tightly the members are clustered, rather than going all over the shop. So that is impressive. You can see the blue shading there throughout the Pacific Basin ENSO region, which means La Nina conditions may be maintained. I am not supportive on that idea, but one thing it does nearly confirm, no El Nino risk at this time....BUT....it can change.

The probabilisitc data sets show that slow waning of the La Nina, this is the model I am aligning myself with. You can compare with the global international agencies there. We have one outlier which is the NOAA (reputable model) that keeps us in La Nina and we have one outlier (BCC) that takes us into El Nino. The majority resolve this event and that is the right call. But note as we head through the outlook period this year, seasonally, the bias is not turning towards an El Nino, and since December's update, the likelihood of another La Nina has grown for later this year. The next 2 months of data will be interesting and verifying the La Nina against the forecast we can see here. I will break that down for you so you can then better prepare.

The BoM model has barely a La Nina, which is wrong. It is already deeper than that and is continuing to strengthen. This model also wants to place us into an warm neutral. I am not so sure on that based on the broader data sets above. One thing I will say, the skill score has not been great in the past year on this model for all climate drivers.

WHAT ARE SOME OF THE LONGER RANGE MODELS SUGGESTING?

Well it is always fraught with danger, the further out you go, the less confidence you should have in specific forecasting. In this situation, I am using the data as a base for you to see where the trend is going and to then help you understand my forecasts as we go throughout the coming months as we head into sowing season and then harvest 2022.


Seasonal Rainfall Forecast - May to July 2022

The exit out of Autumn and entry into Winter, looks very wet if this model is right. It is picking up on the waning La Nina but also projecting a negative IOD across the northwest which is clearly funnelling in deep moisture and rainfall. While that is plausible, it is not probable, not this far out. So just keep that in mind. But with a wet start to Autumn after a wet Summer and then a wet start to winter, if this is right, some areas could be swimming this year. Sowing season will be tricky and very challenging for many areas with above sub soil moisture to deal with and residual flooding. You can never have too much water when staring down a drought, but in this case, we are not seeing a drier trend for the east. For WA, there could be a leaning drier bias and over the tropics that is in line with expectations as we enter dry season.

Temperature wise, it is looking like that cooler trend that is beginning to emerge through the back of Summer will continue through early Autumn and indeed into the early part of winter, this being lead by the extensive cloud cover and rainfall projections. So that is conditional upon that verifying to see temperatures below average.

Seasonal Rainfall Forecast - June to August 2022

The wetter bias continues for much of the nation with a negative IOD in place and warmer than normal SSTs around the north and east o the nation. This will support a wetter look for the east and much of the inland. The east coast tends to be drier in a prevailing westerly so that is nothing outrageous or drought worthy. The west, that is suggesting that the position of the long wave trough, where cold fronts are expected to surge through, may be placed over Bight waters and areas east, so there is no skill in that idea, the model just suggests that is where the frontal weather is likely to be. Northern Australia could see some dry season patchy rainfall.

The heavier rainfall and cloud cover and the potential that the cold fronts will be situated over the southern Bight and through the southeast would lead to more cold air being drawn across the nation's central and eastern parts. Again this is conditional, but the overall trend from this model is for cooler weather.

Seasonal Rainfall Forecast - July to September 2022

Rainfall signal sharpening in line with the strengthening negative IOD idea that this model has. It is not heavily supported but I have showed you that the Euro and UK like the idea of a warmer than normal Indian Ocean so it is plausible, not probable. The nation is looking quite damp. With strengthening IOD and the chance the La Nina may struggle to weaken fully, this is the outcome. But the further you go out, the skill of the model is not great, any model for that matter.

Cooler bias for the central and eastern areas of the nation continuing the theme of the long wave being parked over southern and southeast Australia. That specific detail cannot be forecast with that great accuracy. The north remains seasonal at this time under dry season conditions. Overall temperatures looking to be near to below average through winter.

Seasonal Rainfall Forecast - August to October 2022

Early season onset rainfall for the north with the developing 3rd La Nina and the negative IOD in place as well, combining for a repeat of what we saw last year through Spring. Possible, but not especially high given we are looking over 7 months out from now and models cannot see what is happening 7 minutes out sometime. Something to watch closely. But more on this half of the year coming up later in March. We have to see how the Pacific Ocean behaves through the coming 8 weeks and what the Indian Ocean is doing before a forecast like this gathers more confidence.

That cooler bias continues which again is conditional to where the long wave trough is in relation to the nation. Where the cold fronts are positioned, whether we are in a colder southwest flow through this period more often than not coupled with higher moisture across the nation leading to more cloud cover. To be that specific ahead of this period is fraught with danger. The trend is for perhaps a cooler bias over Winter into early Spring.

Seasonal Rainfall Forecast - September to November 2022

Certainly another flood look for the nation if this is correct, but as mentioned in the previous rainfall analysis, determining this information this far out, there is no skill. It is one idea on the board and I will revisit this again in a month for all you wanting to know what the remainder of 2022 is looking like. Well if this was right, wet, humid, thundery with severe weather events and below average temperatures.

Once again the cool Spring idea is on the table with the negative IOD, the developing La Nina for the third year running with higher than average rainfall for many inland areas and the east and north. That will lead to more cloud cover and less sunshine, less chance for the heat engine to get up and running. But once again is one idea out of many that are on the table. This is just the only model that goes out this far with any degree of detail.

The Indian Ocean Dipole is key to that forecast above coming off, but what are the models suggesting away from CANSIPS?


May 2022

The IOD is expected to start forming a negative phase if this is correct off the global models. The BoM model says nothing is happening. But the Euro and other international models did pick the last IOD event of 2021 quite well which resulted in significant rainfall developing in the late Spring. They do move towards a warming phase but still within neutral values.

June 2022

The Euro getting close to calling a negative IOD event but other models keep it neutral with some impacts of a wetter start to winter if the Euro is right, where other models say seasonal conditions expected.

BoM Model and all the members.

You can see there is a strong upward trend on some of the members according to the BoM model as we go further out, will keep an eye on that, but with international models not interested in that idea, I am not too concerned. This model performed poorly last year in forecasting the event of 2021 ahead of time

So there are plenty of interesting pieces moving on the climate board this year, and there is no rule book when it comes to how many times we see La Nina in a row, or El Nino etc. We just have to go where the guidance is taking us. Right now, no El Nino is a very strong chance and no positive IOD is another idea that is gaining traction.


What that means is that we are left with seasonal conditions, with a tendency for some areas to be wetter than normal.


More to come.






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