Transcript of webinar – Seasonal outlook for Victoria: What are the latest climate signals telling us?
Heather Field:
Hello, everyone, and welcome to today's webinar, Seasonal update and outlook for Victoria. My name is Heather Field, and I'm a climate change service development officer with Agriculture Victoria and will be facilitating today's webinar.
Before our presenters begin, just a few housekeeping items. This webinar is being recorded and will be made available after today. You are all currently muted just to stop background noise. So if you do have a question, please use the Chat function, which is currently explained on your screen, and we'll make some time at the end of the presentation for questions. We do have a large audience joining us today, so we'll get to as many questions as we can. There will also be a quick survey following the webinar. So it'll take only a minute to complete, and we greatly appreciate your assistance in completing this.
Before we commence, I'd like to acknowledge the Traditional Owners of the lands and water on which we're all meeting and pay my respects to Elders past and present. And I'm tuning in from the lands of the Wadawurrung People in Ballarat, and I'd like to acknowledge all the lands on which everyone is tuning in from today.
So, today we're joined by Graeme Anderson, Dale Grey, and Dale Boyd, all from Agriculture Victoria, for a seasonal update, looking at the current conditions and what the climate outlook might mean for Victorian farmers. And our presenters today are likely well known to most of you online, but I will share a little bit about them before we kick off. So, Graeme Anderson is a climate specialist and leads a small team who deliver climate risk services, such as The Break and Soil Moisture Monitoring and On-Farm Emissions Pilot.
Dale Grey is a seasonal risk agronomist, and Dale provides agronomy, climate change, climate and weather analysis for farmers, agribusiness, government, and the media across Southeast Australia. And he authors the Fast Break climate newsletter and produces a monthly YouTube climate update called The Very Fast Break.
And Dale Boyd is also a seasonal risk agronomist and currently works on a statewide technology adoption project that uses deep soil moisture, soil moisture probes and weather station networks. This helps Victorian dryland farmers and advisors interpret seasonal risk information to a decision-making using soil moisture data. And this data is provided and interpreted in an e-newsletter for the grains industry.
So, before we jump into the main presentation, I just wanted to briefly highlight the drought and fire support services currently available in Victoria. So, the drought support package continues to provide practical support for farmers and communities. And on the screen is a summary of what's available.
So, it includes the Farm Drought Support Grants. Grants are up to $5,000 and are available statewide to support on-farm improvements and essential business activities. And farmers in 12 local government areas in the south west can also access an additional $5,000 topper.
We've got the Farm Advisory Service. Farmers can access up to three hours with technical specialists, either on-farm or online. And these can include business advisors, livestock nutritionists, soil and pasture specialists, et cetera. And farmers can choose their preferred consultant.
We've got some group technical events, and we've had plenty of those over the last little while. These are free workshops and events, and they're delivered statewide, focusing on key drought management topics, like feeding livestock and farm water planning. And details for upcoming events are on our Agriculture Victoria website, which I'll pop in the chat shortly.
Looking Over the Farm Gate, this program supports community-led events that promote social connection and mental wellbeing with grants up to $5,000. And these are delivered through the National Centre for Farmer Health.
And finally there, the free and confidential support is also available for financial and wellbeing assistance through the Rural Financial Counselling Service. So farmers can contact the Financial Counselling Service directly and also find out more information online.
So, the next slide has additional targeted supports for south west, and that's to recognise the longer term impacts in that region. So it includes the Household Financial Relief Program delivered by the CWA. And you can see on the screen there the eligible local government areas that it applies to.
And finally, on the next slide, for those affected by the January bushfires, there are recovery grants and concessional loans available to support cleanup, rebuilding, and getting businesses back on track. So Rural Finance is the main point of contact for details on eligibility and how to apply.
So, more information on all of these supports that I've just run through are on our Agriculture Victoria website. So I'll pop a few links in the chat for that shortly.
So, now, with that, we're going to hit over to the main part of today's presentation, and I'll hand over to Graeme to get us started. Thanks, Graeme.
Graeme Anderson:
Thank you, Heather. And welcome, everybody. Graeme Anderson here. And I've just thought I'd give a bit of a plug. We're going to hear from both the Dales today who do some amazing stuff, but we really want to thank Victorian government for investing in their projects. We've got this information that's pulled together and made free for farmers. You can subscribe to monthly updates to get the latest on what's going on with seasonal outlooks and weather patterns, and Dale will go through that with the... But The Break newsletter is a fantastic newsletter. For those that haven't come across it yet, you can subscribe to free. We'll post the links there. And also get regular updates on the deep soil moisture probe network through the soil moisture monitor network. So they're both available. They're available for free. And yes, there's plenty of stuff whizzing around on Facebook and social media about all sorts of other experts, but if you want some good, trusted, sensible information, this is the place to get it. So, just thought I'd throw that in there. And next, hand over to Dale.
Dale Grey:
Righto. Thank you, Graeme. Let's just do a little bit of a summary of the last three months. Looking at February rainfall was wetter in much of the northern half of the state and the eastern half of the state for that matter and a bit drier down there on the, what's that, almost the Surf Coast, I suppose you'd say, and over on the Shipwreck Coast as well. February maximum temperatures were much warmer than normal.
And then in the very last day of February and then into March, we had that very significant rainfall event that was, once again, though, still mainly in the north, not down around the Wilsons Prom and South Gippsland. And the areas bounded in yellow here had up to 100 millimeters in that event, which kicked off both weed and pasture growth in abundance. Yeah, things were going absolutely nuts. And as we'll hear, a lot of cropping people have retained that moisture. Temperatures, because of the rain and the cloud, were more normal in terms of maximums.
In terms of April, though, April was probably drier than we would have liked. It was decile 1, the lowest 10% in much of East Gippsland and an area of sort of Swan Hill up to Boundary Bend. And other areas were below average as well at decile 2 to 3. And April's temperature maximums were much warmer than normal, which really made things grow, but made that moisture that we had disappear quite quickly.
Looking from space here, this is greenness, looking at the state of Victoria. This is an NDVI and an anomaly. So we're looking in the white, pale green, and yellow colours where things are normal compared to normal, and in the browner colours where they're not as green as they should be for this time of the year, and in the darker green where they are greener. And compared to this time last year, a very starkly different map where the forests and the landscape as well, particularly in the north of Victoria, is generally greener than normal. We can see some fire scars there, too. But we can see some areas down along that sort of Central Gippsland, the sandy coast there, areas of the south west, particularly the eastern kind of half, and areas of the north east, too, sort of the western half of north eastern Victoria, where paddocks probably haven't got the start as good and they didn't get the follow-up that they would have liked compared to some other regions.
I think it's interesting just to put this into contrast with the rest of Australia, because I think that if you're in livestock and particularly cattle, that tells a very interesting story because it really does stick out how green northern Australia and the interior of South Australia is and how dry and poor in terms of growth areas of northern New South Wales and southern Queensland are in comparison to normal.
So, moving over to soil moisture and moving to the other Dale, Dale Boyd.
Dale Boyd:
Thanks, Dale. And thanks for that weather observation update. What we've got here is the Soil Moisture Monitoring dashboard, which is got the moisture probe sites that are being calibrated to plant available water. So we've got the key there in the right-hand corner, indicating red is less than 25%, blue is more than 75%, and we've got amber and green on either side of 50%.
We've got a mixture here of cropping sites and pasture sites, and I'll go into more detail with both of those in coming slides. We're measuring deep soil moisture here, too. So, cropping, it's from 30 centimeters down to a meter. Pasture, it's from 10 centimeters down to 80 centimeters.
And as Dale indicated, that significant rain that fell in the 8-day period and ending at the start of March was really significant and it had a real impact on the moisture probe locations in that rainfall zone. Essentially, with the moisture probes, when we get rainfall, we're looking to see what infiltration is associated with that rain. And when we look at the AgVic networks and the sites that receive greater than 100 mil, reflecting its... We've actually got sites that receive more than 150 and even up to 200 mil. We've got sites there at Ouyen, Speed, so a lot of those Mallee sites have detected moisture down at a meter. And also some of the north central sites there at Charlton, Raywood. And we've got Sheep Hills as well that was on essentially a fallow last year, starting at a wetter profile, but the rain that fell was also detected at a meter, where it's a little bit off from detecting down at those deeper sensors.
Rainfall in the zones of 50 to 100 mil includes Birchip, Brim, Taylors Lake, and around Youanmite in the north east. Infiltration that we detected there was around that 60 to 70 centimeters. So we've partially filled some of those moisture profiles, soil profiles, but we've still got some underlining moisture deficits there at depth.
Probably something that people are picking up is that there's a couple of sites there north of Bendigo that are red when others are surrounded there with wetter than 75%. And that's essentially two perennial pasture sites there that have been able to utilise and quickly consume a full profile in the space of 6 to 8 weeks with a lucerne and a kangaroo grass there with their perennial nature.
So, we'll move to the next slide there, Dale. We'll look at a focus in on the pasture sites. With the dashboard, you can toggle between cropping and pasture, and essentially that's just down on the bottom left-hand side. So highlighting here is the pasture sites. And with their perennial nature, they've been able to consume the rain if they did receive rain in that early March period. April, of course, was dry, indicated by the Bureau rainfall charts. And May has been a bit patchy. So we've got a lot of sites that are less than 50% moisture.
And I'm just also highlighted the area over in Gippsland because in terms of information products, there's quite a few that are floating around generated from the moisture probe network. But a bit of a shout-out to James Paulet. On a fortnightly basis, he does an update for the Gippsland sites. And so he's got a great spread there and not only looks at soil moisture comparison to a month previous and this time last year, but he also looks at soil temperatures, which are highly critical. And I guess as it's starting to decrease now, that's why those pasture sites ideally have moisture. And the earlier that they receive those rainfall events and start to build a profile, the better to generate growth.
And also just highlights the two sites north of Bendigo. They're the lucerne and the kangaroo grass there. So, we'll move to the next slide to just sort of showcase the benefits and the highlights you can get from looking at deeper in past just the site locations. And by clicking on those sites, you can obtain more detail. Just some examples here from Birchip and Raywood north of Bendigo. So, what I was looking to do with the dashboard was just put up the essentials. So we can look at the snapshot of the 9:00 AM soil temperature. We can also look at the current soil moisture as it's found through the soil profile. And all these are rated as plant available water.
Birchip, I'd indicated that infiltration was to about 60 centimeters with that March rain event, and you can clearly see that by colour coding it as a soil moisture percentage per sensor. And the speedo or the fuel gauge is another pretty simple way to give that indicator of how full the tank is. As we do know, it's so beneficial to have reserves in place for those cropping regions to draw upon if we experience months that rainfall doesn't meet plant water requirements.
I guess also just the summary from what was happening at Birchip and at Raywood, both sites started at about 20% over summer, and the impact that we were able to observe with the March rain was infiltration to 60 centimeters, which boosted that Birchip site by 50%, and Raywood got a boost of about 80%. It was greater than that with the March rain because it infiltrated down to 1 meter. A little bit of moisture was lost in that April period. But pleasingly, we're now starting to see that 30 centimeter sensor spike up again. So we're starting to see the moisture conditions that are going to permit germination and emergence, and more pleasingly, the connection to those deep moisture levels that were laid down a couple of months ago.
Might move to the next slide, which is another highlight of some cropping sites. I'm just still trying to get a handle on exactly what's happening over in the Wimmera, that due to the varying nature of those rain events that occurred at the end of February, start of March. Fortunately, I've been able to tap into quite a considerable amount of networks, and the Woorak have been generous enough to share some data with me. So they've got 36 probes within the district. So it gives me a pretty good indication of what sort of infiltration occurred within that district and rain events that were sort of around that 50 mil, a little bit variable. But the consensus was that out of those 36 sites, two-thirds have got infiltration from 20 to 40 centimeters. But in terms of the deep moisture accumulation, it's yet to occur. Whereas we look at the Wonwondah sites in that southern Wimmera, more rain, not as many probes to investigate, but the consensus is with what we can acquire the data from, there's a deeper level of infiltration.
I guess I never like to just rely on one information source. So I've also brought in some data from the SoilWaterApp, an excellent model that I utilise to fill gaps where I cannot get data. And they're reflecting similar consensus to what the moisture probes are indicating. So a little bit shallower with the moisture infiltration there at Woorak and that Nhill sort of district, whereas much more deeper infiltration there at Wonwondah and the Bungalally district.
So, I guess I'm just encouraging to utilise all sources of information where possible.
And if we flick to the next slide, I'll finish off on that. And that's certainly acknowledging the contributors to the moisture probe network. So we've got other networks coming in, whether it's Landcare groups, CMAs, or the farming system groups. So we do acknowledge that. And this is something that's commonly put up with Dale Grey's Very Fast Break, but by simply colour coding the changes, so yellow is a greater than 10% change in the past month or 30 days and reflecting that there has been, in those perennial pasture systems in that south west, some improvement to soil moisture, but still generally at a pretty low base, and over there in Gippsland, greater than 10% drier. So, a bit of a miss with the rainfall. And those perennial nature species in the absence of rainfall, they will certainly deplete what's there.
So, really, it's just a shout-out to say utilise your district networks. I find great value in doing soil cores and ground truthing against all these moisture probe sites. And please subscribe where possible to your relevant industry. And reach out for James if you're looking for that site-specific information there over in Gippsland.
Next slide, Dale.
Dale Grey:
It's me. Righty-ho. Marvellous. Let's move to climate here now. This is a sea surface temperature anomaly chart where we're looking at the ocean temperatures compared to normal, where normal is the kind of grey colour. You can see that there's a lot of orange on that map. We can see off the coast of Ecuador some warmer-than-normal water sweeping out across the equatorial Pacific. And the region that we monitor for El Niño and La Niña and this Niño 3.4 region out here currently has a relative temperature of +0.52 degrees C, where a plus 0.8 would be deemed an El Niño.
We have warmer-than-normal water in the Coral Sea, although the expanse of that has retracted over the last month. It was sort of much warmer sort of in behind the reef, and now it's sort of gone a bit further to the north east. And over in the Indian Ocean was just warm in that basin as well.
The Dipole Mode Index measurement, the difference between the west and the east boxes that we measure for the Indian Ocean Dipole, is stock standard normal. The value for a positive Indian Ocean Dipole would be +0.4. We can see we're nowhere near that. We did have some positive-like behaviour in the Indian Ocean back in March, but that sort of very quickly destabilised in April, and it was probably due to tropical processes rather than the actual Indian Ocean Dipole going on.
The real interest, that warm water that's been slowly poking up off the coast of South America along the equator is being driven by this really large area of warmer-than-normal water at depth. And this built up in January of this year when we had a very strong reversal of the trade winds. The trade winds that normally go from east to west across the Pacific Ocean started to blow very strongly from the west, and they pushed warmer-than-normal water underneath the ocean and sent it over. This water was cool four months ago. It was blue in this graph. And now it's been replaced by much warmer-than-normal water, and that's starting to upwell off the Ecuadorian coast, starting to propagate across the equator.
And this is a pre-El Niño-like signature. This is where the torque is coming from. It's because every model in the world can see this big slug of warmer-than-normal water, which has in the past, every El Niño we see generally starts off this way. But I'm at pains to say that just because this occurs does not guarantee that an El Niño actually forms. It's a pre-El Niño-like state.
Over in the Indian Ocean, there's not a lot going on there, really just a little bit warmer to depth off Sumatra. Little bit of cool anomalies been starting to build up of late, but sort of on top of the... underneath the warm anomaly. So there's nothing really over there that really strikes of something that could happen in the future.
Cloud patterns, we look at the junction of the date line and the equator for the absence or presence of more cloud, where less cloud is brown and more cloud is in the blues and purple. And at the moment, the cloud is essentially normal there. We've got more cloud in the northern part of the equator and less cloud in the southern part of the equator. So there is no pattern there. If we had an El Niño, remember that's warm water that comes right across to here, we'd have an abundance of cloud coming off that warmer water and we'd generally see less cloud to the north of Australia. So we don't see that pattern, but we do see less cloud to the north of Australia generally, and generally sort of a lack of northwest cloud band activity going on there as well.
In the Indian Ocean, we have some extra cloud off Somalia and Kenya, and we've got a little bit of less cloud off Indonesia. I think this pattern is still very much a phase of what the Madden-Julian Oscillation is, the cloud wave that goes around under the equator. We're looking at tropical processes here rather than any kind of, well, positive IOD or El Niño-like signature that's going on there. It's just the way we landed at the end of the wet season.
Everything that happens in the coming months will be all about the trade winds and what they do or don't do. Remember, the trade winds go from east to west, as indicated by these arrows here. And the colours show when we've got anomalies, stronger anomalies in the wind. And when we've had El Niños in the past, we have these strong reversals of the trade winds that generally send westerlies from north of Papua New Guinea all the way out to central Pacific Ocean. And we simply have not seen anything like that. The stronger burst that we saw in January and February was kind of sort of situated in here. In the last month, there was a lot of excitement about a double cyclonic storm, which we can see the remnants of up here. But that sort of force did not get anywhere across the Pacific Ocean.
And of course, this is important for warming up the central Pacific Ocean because the trade winds will go from the east in this direction. They'll go from the west in this direction. The ocean will calm off in the centre and allow the sun to get in and warm it up. But at the moment, we just see none of that kind of activity at all. And until we do, there won't be any excitement about an El Niño actually forming properly in the atmosphere at least.
And over in the Indian Ocean, there's absolutely nothing going on there in the last month, although in the last week, there is some stronger westerly wind going on up here, which is interesting because that's not remotely positive IOD-like. We'd expect to see stronger easterly winds going on if there was to be a positive IOD forming.
Going down to the southern parts of the globe now around the Southern Annular Mode, that climate driver that measures how strong the winds are spinning around Antarctica and whether we have positive phase systems or negative phase systems which may be pulling or pulling the systems away from mainland Australia. At the moment, the Southern Annular Mode is diving into negativity. But because we're still in autumn, the Southern Annular Mode has pretty poor response in terms of what that means. It could mean anything.
Once we get to winter, a negative Southern Annular Mode would normally mean the frontal systems have been pushed up closer to the mainland. Whereas a positive Southern Annular Mode in winter would normally mean that they've been pulled away. So, at the moment, it is weakly to moderately negative, and both the American and the Australian bureaus are in sync about what they're predicting in terms of that negative peak pretty in the next seven days coming back to normality.
In terms of pressure, that's where our bogey has been. We've had, on average, a high pressure centred over south-eastern Australia, which has been putting downward pressure on the frontal systems coming through and decreased opportunities to be getting tropical moisture coming down. And this is a phenomena that often happens or has often happened in autumn, often mucks us around, has in previous last couple of years as well.
And the other thing we're seeing that's happened in the last week or two is that the absolute pressure of those high pressures has really picked up. I note that the current one at 1,041 hectopascals down here off Tasmania, which is a massive behemoth of a high moving very slowly and leading to very stable weather. So, higher pressure over the southern parts is never a good thing for rainfall. We need that to move and shift.
The other thing we measure is just the Southern Oscillation Index, which is the difference in pressure between Tahiti minus Darwin. Tahiti pressure is slightly lower at the moment. Darwin pressure is slightly higher, which is why the SOI is at a negative value. It kind of got to about -10. Normally we'd say something like -8 is an El Niño-like value. But just looking at the pattern here, we're kind of being driven by pressure coming from the south rather than tropical pressure in this pattern. And the pattern over Tahiti doesn't look exciting kind of either. So, we need to be watching for that in coming months, too, weeks and months, about what the Southern Oscillation Index gets up to. Because if it goes to -10 or something like that, that could well and truly indicate that the pressure patterns are now starting to sing from the El Niño hymn sheet as well. Whereas at the moment, that's kind of a bit more uncertain about where they're heading at the moment.
So, just in summary, in these two climate drivers, and you'll see why we're talking about these two soon, there's nothing going on in the Indian Ocean in terms of a positive IOD. And in terms of an El Niño, we just have that strong ocean depth temperature being much warmer. There's nothing yet of a great note happening at the surface. The pressure patterns are a little bit mixed. And the trade winds and the cloud patterns are not remotely keeping with El Niño. And we'd need to see something like four to five blue ticks along these things here before you might say that these climate drivers are fully functioning and what they call coupled, coupled together between the ocean and the atmosphere.
Which brings us to the climate model forecast. We have a bit of a mix because we're mid-month at the moment. So we've got some models that have kicked across for May and some that are still April forecast that I've highlighted here in lavender, for want of a better word. And model skill is sort of moderate low, so split between poor to moderate this time of the year. We have every model predicting an El Niño as a result of seeing that warm water under the Pacific. And I'd be at pains to say that this doesn't mean that one will happen. The models are wanting that to happen, but that doesn't mean it will. And not until we see some more interest in westerly wind bursts and things going on up in the Coral Sea.
What is interesting this month is that interest in a positive IOD has gone off. There was stronger interest last month. And now we've got four models predicting a positive IOD, some of them predicting the ocean to our northwest just being warmer than normal, which it currently is, and some just predicting nothing going on, normality. So, a bit more uncertainty this month in terms of what's happening in the Indian Ocean.
Where there is stronger consensus, though, is just in terms of rainfall and particularly temperature. We have a majority of models with drier signals. Rainfall, likely to be in the driest third of the record. There is a little bit of spatial variability in some of those models where the European and the Chinese model both have a drier north of the divide and a more neutral pattern for south of the divide. Neutral meaning anything could happen.
But generally, there's plenty of sniffs of drier there. And given they're predicting an El Niño and somewhat positive IOD, not remotely fascinating to see that, in fact, there are drier predictions with dry climate drivers being predicted. But in many cases, these drier outcomes will be predicated on at least this feature up here actually kicking in, which, as I said, is not guaranteed.
The real crystal ball gazing, which at this time of the year is not worth too much, interestingly, has that El Niño continuing on for spring, so mid of spring if it forms. So it's predicting it to be a longer-lasting event. And given that heat signal underneath the Pacific, that's not unsurprising as well. But we do get a few more models bringing a positive IOD back for spring, too. And El Niño and positive IOD, a coupling of sort of double whammy dry in the Indian and the Pacific Ocean have not been uncommon in the past. And given that suite of climate drivers, still got a number of drier signals coming from the models and warmer, which is unsurprising given those climate driver predictions.
Finally, I just want to finish off on just a bit of basic interpretation of climate models. Here we've got yesterday's model forecast for the next three months, for June to August, for Victoria roughly. There's a lot of brown on that map, and people might be thinking, "Gee, it's not going to rain up in Shepparton" looking at that. And really what you're looking at is, what does this colour mean. We're four colours in from yellow. They're saying there's a 20 to 25% chance of exceeding median rainfall or average rainfall. And in your mind, you need to take that away from 100%. So there's really an 80 to... 75 to 80% chance that the rainfall won't be wetter than average by definition. But we're not getting any information about actual average rainfall here. It's either above or below.
What people may not know is that for a number of years now, you can click anywhere on this map on the Bureau's site. There's a little magnifying glass up here that you can type in any location. And I've typed in Ouyen, Hamilton, Benalla, and Bairnsdale just as examples. And you get these little graphs coming up here where you get the results of the last 99 model runs. That's what this map's created on. But this actually gives you a much more detailed information about those 99 model runs and where they're falling in terms of their rainfall. And you can see at Ouyen that there's a slightly increased chance of decile 1, 2, 3, 4, the drier end of things, where 20% is considered the normal odds of those happening and half the odds of decile 7, 8, 9, 10. People get frustrated when I say the model won't be wrong because the future is somewhere here. It's just that this model at the moment is swinging some of these wetter outcomes over towards the drier, but not discounting that there is still some chance of winter actually occurring.
And the models are always doing this. They're always working on probability. We can see at Hamilton, that's very much a beige, off-white, bone-coloured forecast. It's pretty much 20% essentially across the board there. And you can see that that is also, like, a 50-50 split there between exceeding or not exceeding the average. But basically, that's a forecast there saying plan on anything.
And if we go to that drier forecast up in the north east there at Benalla, we can see quite a low probability of decile 9, 10 and almost a doubling of the odds of decile 1, 2. But you can still see that every possibility is still on the table there, just a very strong increase in the probabilities in towards the drier end. And Bairnsdale also has a pretty much what I'd call a plan-for-anything forecast going on there for the next three months. So, that's it from me, and now moving over to Graeme.
Graeme Anderson:
Very good. Thank you to both Dales. That was excellent. And I just wanted to provide a little bit of additional context because I know some of the folks who've already got some questions there around things like super El Niños and things like that. So just a bit of wider context to add to the mix before we get into the questions.
So, we know this is global average temperatures that have been recorded up to 2024, and you can see how global temps are rising, driven by increased greenhouse gases trapping extra heat. Now, of that extra heat that's been trapped in our atmosphere, 90% of that or actually more than 90% flows into our oceans. And that's pretty important because as we know, the oceans are a flywheel that drive a lot of our year-to-year variability. And it's sort of why we see a lot more orange colours on those sea surface temperature maps these days.
Now, from an El Niño, La Niña neutral cycle, that's all called the ENSO or El Niño-Southern Oscillation perspective, that cycle's going to continue. But noting now, we're also on a warming trend. So every decade or so, we're likely to see an El Niño and some warm water pop up out there in the Eastern Pacific that's warmer than any previous events, and that's why you get some of these terms like super El Niños. But anyway, we're living in interesting times. It also means it's increasingly hard to find any true analogue years in the past because those sea surface temperature maps that we look at today are much warmer overall than what we've seen in the past. So, while historical records for rainfall are a great place to start, it's also important to know that some big things are sort of happening out there which drives Victoria's weather patterns.
So, the next slide, Dale, is one of my favourite images. It shows a wider picture of the Southern Hemisphere, a part of the planet. Now, Australia's climate science come a long way in terms of understanding what are those key drivers and influences of Victoria's wetter or drier seasons, and we know this info better than ever. So we live at the crossroads of some of these large-scale climate drivers, and how they interact explain a lot about our past and future variability.
So, you'll notice the big Pacific Ocean, it's huge. It's almost half of the planet. So when the Pacific Ocean's doing something a bit different, it can affect the seasons and weather patterns across multiple continents. So, warm water sloshing around out there has always played a big part in that wetter and drier years. So, on the map, you'll see some key features here. So that Pacific Ocean, El Niño-Southern Oscillation out on the right, but also we've got the Indian Ocean Dipole out to the left, really key cycles. And depending on where the warm water goes, where all the cloud is, that they really do drive a lot of our moisture circulation and pressure patterns that sometimes those oceans are in helpful moods and sometimes they're not so helpful.
And down south, we've got the Southern Annular Mode and also the subtropical ridge, which are sort of really important in terms of the triggers for how that rain falls out. We like to think of them sometimes as the four climate dogs that round up Victoria's rainfall. And just like normal sheepdogs, when things are going well, it makes farming easy, but if the sheepdogs start misbehaving, then that makes the job of farming harder.
I just sort of like to say that if you're looking for past impacts, I mean, we know if you go back to some of those really big dry years that a lot of farmers will remember, such as back in 2006 or 2015, that was when both those big oceans, we had an El Niño in the Pacific and a dry phase of the Indian Ocean Dipoles, so an IOD positive at the same time. So we know some of those dry years or the risk of dry years is when both those oceans are in a foul mood when it comes to making rain.
And the big wet years, when you think about some of the Murray-Darling flooding in that 2010, 2022, in those years, both out in the Pacific and the Indian Ocean Dipole, both of them in their wet phases. So we know that their fingerprints are all over that variability. But of course, most years they're actually not teaming up like that. They're doing a bit of one thing or a bit of the other. But anyway, the key bit is, make sure you get good commentary because what The Break commentary and newsletter does each month just tells you about what each of these are up to. And there's one thing to hear about what's happening with forecasts and models, but then we're more confident on some of those forecast models when you can see from month to month and actually all of the bits falling into place.
I just got to throw in that down south these important climate features. The Southern Annular Mode represents those westerly winds that are pretty much down there over the Southern Ocean, and that's the conveyor belt that brings us all our cold fronts to southern Australia. And then above that, we've got Ridgy, climate dog Ridgy, subtropical ridges where the zone, where the high pressure patterns like to track along.
Now, both SAM and Ridgy drive a lot of our variability, but they're also influenced by climate change, because there's increased global heat actually shifts some of these weather patterns towards the poles, and in our case, shifts them southwards. So, the basic physics is that as the planet warms... The hottest part of the planet is along the equator, and that's what we call the tropical zones. As the planet warms, these tropical zones expand further from both sides of the equator. And as the tropics expand, it then nudges the overall weather patterns and those westerlies towards the poles. And so, for southern Australia, that means that those key drivers of our reliable autumn, winter, spring rainfall are slipping southwards more often.
So, that's what's sort of pretty well known by the climate scientists. And that's what shows up in a lot of the climate change models, which they say this is a bit different to good old-fashioned variability, which is why they expect to be a bit warmer than dry more often. But we're still going to have lots of variability in the mix.
So, the next slide, I'd just like to give a good plug before we finish to a useful little tool called the Local Climate Tool. It's a great little resource, and we'll post the web link in there. But basically, you can go to it and look at the past effect of any of these phases such as an El Niño or a La Niña seasons or the Indian Ocean Dipole wetter or dry phases. You can go to that and see how have they affected your district's local rainfall.
So, next slide. Thanks, Dale. So, when you get there, you can see at the top, you'll get a button there and you can click which climate phase you're interested in, and then you can click the month. So, I've just clicked here June to November. So I'm interested in that period, that sort of winter and out to the spring finish. And I clicked on El Niño years and it then pops up these sort of little chocolate wheels that tells you, well, the red is in the driest third of years, the blue is the wettest third of years, and the yellow is sort of the average third of years. You can see that in and you click that for an El Niño, you can watch those graphs shape because more than half of them were dry, but there was still the odd wet one in there, even in El Niño years.
In the next slide, Dale, if you click on one of those wheels, you can then find out for the locations, and I've just banged on to Longerenong's there, but then you can start to get a bit more detail about your local rainfall and what's played out there in those previous phases.
So, the next slide. Thanks, Dale. This next one's pretty handy. I like this little table. This one for your district is worth printing out and hanging up on the office wall because it's got... And if you look at that top one there, Dale, the deciles, decile 1, 2, 3, 4, all the way up to decile 10, shows that all years, from driest through to the wettest, we're just talking about splitting them up into the driest 10% of years, and decile 10 is the wettest 10% of years and everything in between.
But you can just see how those deciles have changed depending on what combination of either neutral, El Niño, La Niña, IOD, or combo years happen. And look at that horrible one Dale's hovering on now. When the El Niño combines with the positive IOD, the chance of a decile 1 at Longerenong really does increase. So, this is useful. Jump on the site and crunch this data for your local district and put it up there.
The other bit I'd just like to point out, the useful bit of this, is quite a few farmers and agronomists we've worked with like to see in the next slide, Dale, is the... Oh, yeah, no, you could put out your annual graph there, which shows just the annual rainfall, and it's colour coded into those previous climate phases. Another one worth printing off and putting on the office wall.
Next slide. Thanks, Dale. One of the things that some of the agronomists and farmers like to do is you can actually go into that and for that location and then look at, for the El Niño years, what was the actual monthly rainfall and some of those season finishes, and that's where it's quite interesting. And you can see here these, again, just a bit of a series of El Niño years. And Dale's got one of the super ones marked there in the past. And it was an average year that sort of yellow indicates, well, it was an average finish in that year.
Now, if you head down to the next slide, Dale, one sort of thing which really is about our memory bias, you can see these are other El Niño years. And if you look right at the bottom, 1982 was a very dry year. Yes, it was an El Niño. 2006, another one there, very dry.
So, often when farmers hear the word El Niño, everyone is assuming it's like that. But just remember there's been 28 past El Niños. And if you go to this site, you can get a look at how the whole 28 of them in the past were. And every El Niño is going to be somewhere in that range, basically. And the important bit we talk a little bit and some of the farmers hearing about super El Niños is that there's super El Niños in the past there that have been drier or average. So super doesn't guarantee any particular outcome.
And I guess our next slide, I think, Dale, we sort of talk about that. And it's not really helpful. You're hearing about in the media, I know a lot of farmers are anxious about this, hearing the word super El Niño or sometimes all sorts of words are used to explain it. It's not overly helpful for Australian farmers, I don't think. And most of the climate scientists we speak to don't like the term. But it doesn't stop people all around the world writing articles, and you get more clicks if you make those headlines more exciting. So, it's creating quite a bit of unnecessary angst.
But basically, an El Niño occurs when the Pacific and the ENSO zone out in the Pacific exceeds 0.8 degrees above normal. And the word super gets thrown around anytime it's perhaps more than 2 degrees above normal. So, that's why we're hearing a bit about what might happen this year. And as I said, with climate change, every 10 years or so, it would pop up again probably a bit warmer. So we're going to have to get used to that.
Now, the impacts on Victoria's rainfall, there's really no clear link between how strong that temperature increases in the Pacific to any individual rainfall event. There's just a huge range of things that can happen. We do know that overall El Niños can increase the odds of drier conditions for our winter-spring. But still doesn't guarantee it because it's also about what the Indian Ocean Dipole, what local sea surface temperatures are up to and local cloud patterns and all of that stuff. So, don't just assume the worst. It's all about what's going to happen here. And that's why we're saying with The Break newsletter, yes, there is some warmth out there under the Pacific, but to see whether that translates into next month where does it surface or not, does the atmosphere start to lock in, does the cloud patterns and the wind start to shift, does the SOI start to drop, they're all the things that we would need to be seeing and hence get regular updates on that.
So, that's probably... What's the next slide, Dale, before we finish up and open up to questions? Stay up to date, because this stuff is fluid, and then in autumns, we talk about predictability barriers. We know these oceans have a big influence in our winter and spring. And sometimes the models get it right and sometimes they get it wrong. So, we're usually more confident when you see the models predicting something. And then as each month goes on, you can see those key chunks of information actually change. So, that's what we'll be watching. It hasn't happened yet.
So, understand how past ENSO events have affected your region is a really good place to start. There's 28 El Niños in the past. They're not all like that driest one that you can remember. So there's a big range of outcomes there. And the key bit, too, make decisions on what's knowable, know your stored soil moisture, how much you've got, know feed/pasture on offer, fodder-water reserves, which I know is really mixed across the state, and those things like your own stocking rates and markets. Map those things out and just monitor them and have decisions as we go along.
As Heather pointed out, there's great advice and support that's available. And a little tag. The Bureau does a really good job with their seasonal outlooks. And actually read the text because what's really important, a lot of work goes into the Bureau's rainfall outlooks and very carefully worded. So don't just look at the map and actually read what they're saying because that's often really useful.
So, thanks, Dale. I think that's probably rounded it up, and we can get into a few questions.
Heather Field:
Wonderful. You've done a great job, all three of you, in presenting a wealth of information there and actually addressing a few of the questions that have been popping in as well. So, that's been great.
Just looking at the questions, there was one that I saw about late spring frosts, Dale Grey. "So, there's data about late spring frosts, October, November. Been a few frosts in the north east of Victoria. And traditionally, a bad late frost only happens once or twice a decade. So, what are the chances that could happen again?"
Dale Grey:
Well, we know El Niño in particular, but also the positive IOD increases the odds of frost, because if it's drier and clearer skies, we stand a chance of potentially just increase the odds of frost if those two climate drivers actually form. So, until they'd form, I'd say normal odds, nothing to see here in terms of increased risk. But if either of those two were to form, I would say there would be an increased chance of frost, correct, in spring.
Graeme Anderson:
Yeah, thanks, Dale. And Heather, I see Tim's got a question in there just about, "Does it really matter if we get an official El Niño or not? Because if models are predicting a dryer forecast, don't we end up with a similar sort of result anyway, like a dry year?"
My thoughts on that one is, yes, actually, different climate drivers can get a lot of the commentary, but really it's the overall forecast, which all of these climate models now are trying to take the overall weighting of all of those things put together. And that's why you're best just looking at that overall seasonal outlook.
And the beauty of what Dale does together so that you don't have to, he reads across and clicks hundreds of buttons to get those 12 different leading global forecast models and put them all on the one sheet. So, there's quite a bit of work there behind the scenes. But that's sort of a bit like a footy tipping indicator about what's the vibe. Sometimes they're all over the place. Sometimes when they all start to gang up on a particular way, it sort of makes things look a bit more likely. But again, you've still got to see how things change each month about, are the models onto it and is it happening? Or sometimes we can have the models all onto something, and then month by month, you look at it and there's no shifting cloud pattern, nothing happening, and it's a bit of a false one. So, that's why don't go locking anything in just yet. [inaudible 00:54:26], Heather-
Dale Grey:
And just adding to that, Graeme, the March forecasts from a lot of models were drier in the absence of El Niño and positive IOD, particularly for April, because they were sensing that those pressure patterns, I suspect, were going to move against us, which is what they've done. And so, yeah, the climate models are able to elucidate a lot of that kind of stuff, or we hope they can. The best chance we have of helping to integrate, I suppose, all the things that are going on, not just is there an El Niño or is there a positive IOD, but how's the atmosphere and the ocean interacting and playing out?
Graeme Anderson:
Yeah. Dale Sharon's asked, "Heard from another forecaster that the El Niño will be too far north to affect Australia's weather. What are your thoughts?"
Dale Grey:
That's an interesting question. I mean, at the moment, we don't even have one. I mean, they nearly always, if they form, they will form along the right on the equator. So I don't think it'll be too far north. I do wonder if there are questions about that wind that was being stirred up because the wind that we've seen stirred up by the cyclone in the Northern Hemisphere hasn't done what we would have thought it would do.
And in past El Niños, what we've seen perhaps is not... And as Graeme said, there's no link between how warm the central Pacific gets and any drying pattern on eastern Australia. What will be more worrying is how cold the water gets to the north of Australia in either direction. And if it doesn't get cold, well, maybe all bets will be off there as well. [inaudible 00:56:18] playing out.
Graeme Anderson:
And Dale, that wasn't... We had some interesting stuff happening in 2023, wasn't it, where there was some models predicting sort of an El Niño and [inaudible 00:56:27]-
Dale Grey:
It's almost a cookie cutter, almost a cookie cutter of our current situation.
Graeme Anderson:
Yeah. Well, it fluffed around, but didn't actually form until really late in the year. What got its gear, it finally sort of got into the El Niño right at the end of the year. And so, it's less of an issue for us for our summer rainfall in southern Victoria that if you were going to be concerned about potential El Niños, IOD, it's probably the ones that form earlier and send the signals earlier in the season. If in the next two or three months we see it all... if you see the sea surface temperature changed into the El Niño, you see the trade winds go the wrong way, see the cloud disappearing off Indonesia and all heading out into the central Pacific and the pressure pattern things, that's when Dale would be starting to get a bit more gloomier in the mood, I guess, about that rainfall.
Graeme Anderson:
Yeah. But it's fair to say farmers... And we've got a weather event coming on the weekend and who knows what happens with that, but there's quite a bit of variability on the weather models. But the Pacific can be doing one thing, which is not helpful, but if the Indian Ocean is still in gear and offering some moisture to flow through those northwest cloud bands, then we can still snag some good years. So, that's why the overall sort of outlook, and that's what things like the Bureau's ACCESS model, it's measuring the physics playing out for all of those things combined. So that's why they're pretty good just to go to that and stay tuned to that.
Heather Field:
Thanks, Graeme. Just looking at the questions, we've covered a fair bit on the El Niño, but there is one about, "Would it be true to say that for southern Australia, the IOD is more of a factor indicating drought than El Niño?"
Dale Grey:
I don't think you can hang your hat on IOD without including El Niño in the mix as well. If you look at them in isolation, they've both had a similar effect over time. They both increased the odds, 50 to 75% chance of spring rainfall being in the lowest third of the record. And then as Graeme said, if you combine the two together, well, then the odds increase of drier.
But it's interesting because most people may not know that a lot of the moisture that falls out as rain over Victoria has once evaporated off the Coral Sea to our north east. I'm pointing in a different direction. But we're just kind of a bit counterintuitive because that's kind of not where our weather comes from, but those westerly weather patterns that come across, getting northwest cloud bands, pulling cloud out of Broome, the actual moisture that's come in that's forming that cloud may once have evaporated off the Coral Sea. So, that's why the Pacific Ocean does have such the influence as it does. And the Indian Ocean is often a bit of a killer. It puts the high pressures in the wrong spot and can sort of kill your connection to tropical moisture, irrespective of [inaudible 00:59:51]-
Graeme Anderson:
Now, Luke's asked the question, Dale, [inaudible 00:59:52]-
Dale Grey:
Sorry, Go on.
Graeme Anderson:
Luke's asked the question, "What point does the increase in global temperatures trends start to override the current models? And does it mean they're no longer work or useful?"
So, I guess what we'd say is that no matter what happens to future variability, it's still driven by the live physics. So all of these global climate models are just dealing with the live physics. So they already know and they're picking up those warmer signals. And really, for how things like the El Niño-Southern Oscillation works, it's still going to be about where the warmest water sits out there along the equator. And then if the atmosphere starts to match that and you get extra cloud and the trade winds shifting, those processes will still be happening.
I guess a wider observation would just be that there is a possibility that as some warmer bits pop up, and I think 2010 was a good example of that where we had warmest on record sea surface temperatures to northern Australia. So we had the big La Niña and the big IOD negative happening, but that accumulated extra heat. Suddenly the warmest ocean was in our neck of the woods, which then fueled extra moisture to then feed into our weather patterns.
And so, that's sort of the bit that's about the variability versus climate change, is that these swings in variability will continue like good old-fashioned variability, but every now and then they'll come with some extra knobs on top. So, that's probably... That fair, Dale?
Dale Grey:
Oh, the climate models won't model... They won't care. If it gets warmer, the maths, as Graeme says, will respond. And they might start predicting some weird things that we've not seen before because of that extra warmth. But no, I don't think they'll start putting out unbelievable results because they're getting warmer. And if anything, they're our best chance of getting results of predictions that are believable, I think.
Graeme Anderson:
And Chris has just asked about the Antarctic vortex, and basically that's what we're talking to with regards to the Southern Annular Mode. The longer term sort of trend and what the climate change models expect is, as you warm up the planet, warm up things, the tropics expand from the equator and everything gets nudged towards the pole. So, that conveyor belt for all those southern fronts just slips out a bit more often or a little bit weaker. So, that's sort of the climate change signal. But we'll still have seasons where if SAM's in negative mode and it's during winter, it can still get quite wet. But it's variability, but there is a probably longer term trend there we'd expect to see.
Anyway, Heather, how are we going time-wise? Have we burnt it up?
Heather Field:
Yeah, we probably are at time. We've got through most of those questions. And we did have a big crew online today with a bit over 200 online. So, yeah, great to get lots of interest and some great questions there coming through.
I have popped a number of links into the chat, but if anyone's having trouble accessing those, they will be provided with the recording, which will go out to everyone who has registered. So, if you can't manage to access them in the chat, don't fear, you'll have them in the recording that'll be sent out hopefully later today.
But if there is nothing else burning, I will close it out, given we are just a bit over time. And just want to thank Graeme, Dale Grey, and Dale Boyd for some great presentations today and very much a timely topic and lots of interest in hearing what's been happening and what will be happening.
We do have a survey that will pop up on your screen in the browser when you do close out of today's webinar. So really appreciate if you can fill that in. It'll take about a minute to do. And yeah, we do look at that information and take your feedback on board.
As I said, there will be a recording made available. So if you want to catch up on anything again that you've heard today, that's a great opportunity to have another look. And yes, stay tuned for future webinars that we might have coming up. They'll definitely go out to everyone who's registered for today's webinar.
So, with that, I'll thank everyone again for your engagement and look forward to seeing you at the next AgVic climate webinar.
Dale Grey:
Best wishes.
Graeme Anderson:
Best wishes. Thanks, Heather.
Heather Field:
Catch you next time.
Graeme Anderson:
Thanks, Dales. See you.