Transcript of the which weather systems cause Victoria's rainfall, and how are they changing webinar

Heather Field:

Our webinar today is on which weather systems cause Victoria's rainfall and how are they changing. In this webinar, Acacia Pepler from the Bureau of Meteorology will highlight how the importance of different weather systems varies between different parts of Victoria, and what changes in lows and fronts in recent decades can tell us about rainfall declines during the cool half of the year.

Heather Field:

Following Acacia's presentation, we will also hear from our two panel members, Lyndon Kubeil and Dale Grey, both from Agriculture Victoria. Lyndon and Dale will share their thoughts from a sheep and cropping perspective about what this means at the farm and paddock level and what can be done to manage it. I'm looking forward to our presentation and panel discussion today.

Heather Field:

I'll hand over to you now, Acacia. I'll just do a little bit of an introduction. Acacia is a climate scientist in the climate research group of the Bureau where she researches Australian climate variability and change with a focus on climate extremes. Acacia received her PhD from the University of New South Wales in 2017, where she studied east coast lows and severe low pressure systems that can cause very heavy rain in the east coast of Australia. Over to you, Acacia, for your presentation. Thank you.

Acacia Pepler:

Thanks, Heather. Today, I'm going to be talking about some work we did as part of the Victorian Water and Climate Initiative. This is work funded by the Bureau and CSIRO but particularly the Victorian Department of Environmental and Water and Planning. It's the water group within DELWP. The focus of this much larger project, VicWaCI, has been about getting improved information on past and future climate to support water sector in Victoria, although, of course, the information is applicable to a large number of different areas, including hopefully all of you guys listening today.

Acacia Pepler:

There are a lot of different things that have been studied as part of the VicWaCI more generally, including the work I'm going to talk about which is the different weather systems that influence rainfall in Victoria and their changes. But there's also been work on changes in stream flow, projections of stream flow and the role of climate change in the Millennium Drought, changes and extreme rainfall across Victoria and also the broader scale circulation changes in the atmosphere and how that's influencing Victoria.

Acacia Pepler:

So there's a lot of interesting work going on there. The synthesis report is due to be released sometime this week hopefully. So if you're interested to find out more about the broader program, there's a link at the bottom left of my slides, just water.vic.gov.au/climate-change. This just forms a very small part of some of the work that's going on in VicWaCI.

Acacia Pepler:

The work I'm talking about today is talking about what weather systems influence Australia's rainfall. There are a lot of different ways that I could be defining or referring to weather systems, I can't talk about all of them. This research is really focused on three of the most significant types of weather that influence us in Victoria and across Southern Australia more generally. And there are pictures on the slide.

Acacia Pepler:

First off, in the top left, I have a cyclone or a low pressure system. You can identify these on a weather chart by seeing an area that's got lower pressure surrounding environment often with a bit of L and X in the middle of it and then it's surrounded by those pressure contours. A low pressure system, they can produce quite a lot of rainfall and they can have quite a large area. As you can see from this map, they're always big in Victoria and they can also sometimes hang around for a long time.

Acacia Pepler:

Lows are particularly familiar to people from Gippsland who are well acquainted to the special types of lows called East coast lows, but they can of course happen across all of Southern Australia. The second type of weather system I'm talking about today is on the bottom left. Another one that's quite familiar to many people who look at the webinars. It's a cold front. It's marked by that blue line with the little blue triangles. It's an area where cooler air is coming in and replacing warm air causing the air to rise and rainfall.

Acacia Pepler:

Generally, if a cold front comes through, they can be quite fast, but again, they have cover quite a large part of the state. You get a change from those warmer northerly winds to cooler southerly winds. And they can both be important for rainfall and also particularly in the summer, they can make a big difference to things like heat waves and fire.

Acacia Pepler:

The third type of weather system I'm going to talk about on the right is on a completely different scale. Lows and fronts, we're talking about things that last a day or multiple days and cover areas larger than the state. Thunderstorms, on the other hand, will cover a few tens of kilometers and they'll last a year. And then, an individual storm might last half an hour or a few hours.

Acacia Pepler:

But what we're looking at is the environment that favor thunderstorms to happen because, when the atmospheric conditions are right, you can have a lot of thunderstorms developing over a period of time and over larger areas. This particular figure here is just the radar from a day back in 2017 where there was some quite severe thunderstorms in Melbourne which caused things like heavy rainfall and strong winds and hails. Some thunderstorms can even cause tornadoes. So they're very important for that extreme weather.

Acacia Pepler:

This is just an example of how not everywhere in Melbourne was having a thunderstorm, but there are quite a few different little thunderstorms popping up in the area. To identify thunderstorms, we're using a similar approach to what you'll see on thunderstorm warnings, where you would see a big area of the state highlighted in yellow saying, this area has the conditions favorable for thunderstorm activity.

Acacia Pepler:

That's what we're looking at. We're looking at conditions that favor the activity of thunderstorms. Those are the three weather systems. What's interesting about this work is that, these weather systems can all occur on their own but they don't have to. You can see that in the top left, that weather system has cold fronts in it and most or many low pressures too. In very severe events like in the 2016 storm that took down all of those power lines in South Australia, you can very easily have all three things happening at the same time.

Acacia Pepler:

We're starting with our three types. This turns into seven different types of weather systems because we're separating cyclone only, front only, thunderstorm only, for instance, where those two or even three of the systems are interacting and occurring in the same area on the same day. And those will be very important, which I'll show you during this talk.

Acacia Pepler:

This chart here shows, in the yellow bars, what proportion of days are influenced by each of our seven different weather systems. So the three solo types and then the four combined types of weather systems, and then all the other days. Other days include basically any day that don't have any of these three systems. So it could be a high pressure system, it could be a warm front, it could just be that we've got strong westerlies across the state or northerlies or easterlies.

Acacia Pepler:

About half of the time is classified into one of our seven types and about half of the time is classified as other. But if I stopped looking at, not frequency, but rainfall here shown in the green, you can see that others are having much less importance. While others occurred on 50% of days and only caused 10% of rainfall, the vast majority of rainfall averaged across the state of Victoria is caused by our weather types.

Acacia Pepler:

This is where those combined types start to become really important because relative to the frequency, the cyclone plus thunderstorm, front plus thunderstorm and cyclone plus front plus thunderstorm are really important for total rainfall. This shows up even more if we start to look at those heavier rainfall. Here, I've now just added a few more bars for days above one millimeter so just moderate rain days and days with heavier rainfall measures, 10 millimeters or 25 millimeters.

Acacia Pepler:

What you can see is, the other types are even less important. So by the time we're getting to these really heavy rainfalls with 25 millimeters, basically all of the days in Victoria are captured by one of our types. Everything like cyclones and thunderstorms, apparently, there are proportional amounts of those events called biosystems front only days, which are quite common to your lighter rain days and not very important to the heaviest rainfall.

Acacia Pepler:

But those combined types, cyclone plus a thunderstorm and cyclone plus a front plus a thunderstorm only cause about 10% of rainfall or rain 10% of days, but they're causing more than half of those heavy rainfall events. So those combo types are really important to heavy rainfall in Victoria. Surprisingly, the weather systems also vary across the states.

Acacia Pepler:

The figure I was showing before was average across the state as a whole, whereas this takes those green bars as the proportion of total rainfall due to each weather type. Look at how it varies across the state. It's consistent with what you know if you're someone who lives in one of these areas. In Gippsland where you get East coast lows, there's a much larger proportion of rainfall from cyclone only days than the other parts of the state.

Acacia Pepler:

A front only or a cyclone and a front is particularly important for rainfall in parts of the Southwest. Thunderstorms are more important the further North you go. Along the Northern border, thunderstorm only days start to become important. Those triple storms are really important up in the Northwest of the state.

Acacia Pepler:

We can actually use this to identify different regions of the states that has similar rainfall characteristics, which quick pleasantly comes out to be consistent of a lot of the work that has already been done in previous projects such as the previous VicCI and SEAcI initiatives and what we were already expecting so that, generally, Gippsland is its own special piece and then the Northern and Southern parts of the state have different rainfall characteristics.

Acacia Pepler:

The contribution of these weather systems also varies throughout the year. On average, we get more rainfall during the cool half of the year, during the winter months, than we do in the summer months in Victoria. That's particularly due to changes in the cyclones and fronts. So there's a large amount of rainfall that comes from cyclone only, front only and cyclone plus fronts during the winter months so June to August in green here, but they're not so important during the warm half of the year.

Acacia Pepler:

Whereas, thunderstorm-related rainfall can occur at any time of year. But these triple storms that are really important to the heavy rainfall are particularly important during spring and summer. So we've got that variability as well. That changing frequency of cyclones and fronts throughout the year contributes a lot to why Victoria has the rainfall patterns that it does. In the summer, cyclones and fronts move further South and are least likely to impact us.

Acacia Pepler:

I've told you what weather system matter and what data we're using, why are we even doing this analysis? The reason is, we're trying to understand what's going on with changes in Victoria's rainfall. I'm sure it'll be no surprise to anybody who lives in Victoria and who's lived through the Millennium Drought that there's been a general decline in cool season rainfall over the last several decades.

Acacia Pepler:

This figure here shows, in blue, rainfall during April to October which is the cool water season that we're using as part of the VicWaCI. In the orange here shows November to March of the past years. There hasn't been very much change in rainfall during November to March over the last century with exception of some very heavy totals during that 2010 to 2011 El Niño that we all remember so strongly. But in contrast, there has been a decline in the rainfall during the cooler months of the year.

Acacia Pepler:

And that was very noticeable during the Millennium Drought but it's also continued after the Millennium Drought. If you ignore the very wet cool season of 2016, rainfall during the cool months of the year has continued to be below average over the last decade since the Millennium Drought nominally ended. Overall, and this status unfortunately ends in 2015 so we can't look at the last few years, but we can see, okay, there's been 16% drop in cool season rainfall between 1979 to 1996 and 1997 to 2015.

Acacia Pepler:

Why is that? What weather systems are contributing to that? That's what I show in this figure. I'll explain everything. It looks a bit complex, thank goodness. What I have here is, I've got four seasons. Autumn, winter, I've defined spring here as just September to October after some discussions of Lyndon and Dale, and then thrown November into the summer cattery. So summer is now November to February. And this again is average across the whole state.

Acacia Pepler:

What's the total change in millimeters in rainfall between 1959 to 1996 and 1997 to 2015 broken up into the change in rainfall from each of the seven types? In blue, I have cyclone and front-related types, yellow is thunderstorm only and then in orangy and reds I have thunderstorm types. What I think should stand out is that, in all seasons, we had a decrease in both blue columns. So we've had a decrease in rainfall related to the cyclones and the fronts.

Acacia Pepler:

But that's especially strong during the winter months which is not necessarily surprising because, as you saw earlier, winter months are also windy which caused the most rainfall to begin with. For the other types of weather systems, it's a lot more patchy throughout the year. For instance, those cyclone front thunderstorms which are important to heavy rainfall, have shown a big decline in September and October but they've increased in autumn and winter. So there hasn't necessarily been a big overall change and not necessarily a statistically significant one.

Acacia Pepler:

But we are starting to see a more consistent signal of an increase in these thunderstorm-related types, thunderstorm only and the combined weather systems, during the warm months of the year, November to February. I can, again, group these categories together that have similar patterns. I'll group these three blue columns together and I'll group all these orangy red ones, the ones related to some of the thunderstorms, together and then we can look at how rainfall is varying again across the state.

Acacia Pepler:

That's what I show here. Again, to the four seasons. This is again, the total change in millimeters rather than being a percentage change. On the top, we have the decline due to rainfall from lows and fronts. This has been declining again in all seasons, but the change is actually pretty consistent across the states and across the seasons. But of course, in winter in the Southwest of Victoria, lows and fronts cause a lot of rainfall so that's where we're seeing this really large decline.

Acacia Pepler:

In the contrast, when we look at those thunderstorm-related weather systems on the bottom row, there's very patchy trends. Generally, here, it declines in most of the seasons that matter for agriculture and water, but then we have those strong increases in thunderstorm-related rain during the warm months of the year, especially in the Northern part of the state.

Acacia Pepler:

And then, we can also ask you, what's causing this decline in rainfall? Is it that we're having fewer fronts, is it that they're less likely to produce rainfall or is it that they're producing less rainfall when they do rain? And the answer to that is, it's predominantly because they're not as likely to produce rainfall. This figure here shows, again on the top row is three low and front types, the middle row, the thunderstorm types and the bottom row is other days, just so that we can be comprehensive.

Acacia Pepler:

There's a total change in the days that either exceed one millimeter so the rain days associated with these weather systems on the right, or the ones don't have rainfall on the left. The main takeaway from this figure is that, again, we've had this really large decline in the frequency of lows and fronts that produced rainfall across the state, but especially in the Southwest. I should specify that this particular figure is for the whole year lumps together rather than separating out the cool half and the warmer half.

Acacia Pepler:

In contrast, we can see patchy changes in rain days related thunderstorm and there's been a little bit of a decline in other rain days with things like Westerlies or whatever. What's interesting is looking at the change in dry days. In the middle row, you can see that areas that have had more thunderstorms generally have both more dry thunderstorms and more wet thunderstorms. That's especially in the East and the South of the state.

Acacia Pepler:

But the patterns with dry lows and fronts are very different. While we've had this big decrease in the lows and fronts that produce rainfall, there's been no change or a bit of an increase in the frequency of dry lows and fronts. In fact, if I look at just fronts, we can see that if you add those two together, there's no change in fronts overall, it's just that we're having more dry fronts and fewer wet fronts. That's something we intend to look into a lot more because, of course, dry fronts can be very important for things like bushfire risk which is a good thing to know what's going on there.

Acacia Pepler:

If I look at heavy rain days, the patterns are a bit patchier but they're fairly similar. We see decreases in 10 millimeter days associated with lows and fronts and decreases in 25 millimeter days associated with lows and fronts. Those are most common in the east of the state but they're decreasing there. And then, very patchy changes in these heavy rain days associated with thunderstorms and no real change in the heavy rain days from other systems because other systems don't cause heavy rain days.

Acacia Pepler:

We can use this information to break down, okay, the total change in general rainfall, again, in millimeters across the state, how much of it can be explained purely from the changes in frequency you're seeing or are there any additional changes in the intensity of rainfall? This all varies, basically, all due to the frequency. So you can see in the middle top is the rainfall change we would expect purely based on the observed decrease in lows and fronts that produce rainfall. And it's almost identical to the total change we have seen in rainfall from lows and fronts, the remainder change in intensity doesn't contribute much.

Acacia Pepler:

What does these all results mean, what are they telling us? Well, we've seen that different weather types have different impacts on rainfall and this varies across the state in the different seasons and different intensities. It's really important to understand how these different systems matter in different parts of the state. Plus, we know that the changes that we've seen and the changes we're going to see in these different weather systems are different.

Acacia Pepler:

Because the changes we've seen are reasonably consistent with what we've seen from climate change, global models consistently expect there to be fewer cyclones around Southern Australia. This is consistent with the work I've shown here, that we've already seen a decrease in cyclones and the associated rainfall, and also previous work that was done almost a decade ago showed a similar thing that we're seeing there's large variability in cyclones at all weather.

Acacia Pepler:

Other types are going to be less important for the rainfall in Victoria in the future. That's something that's particularly important to the areas where cyclones contribute a large amount of rainfall. On the other hand, projection of thunderstorm is much harder to do because they're so small in scale. But generally, we think that the most extreme rainfall summer months is likely to become more intense.

Acacia Pepler:

Again, that's consistent with what we've already seen in this work, that there's increase in thunderstorm-related rainfall in parts of the state, especially in the North. Here's just a few papers published as part of this, the new thunderstorm data set as well as the data set of weather types. Thank you everybody for listening. Again, if you want to learn more about any of the work, this is all part of the broader Victorian Water and Climate Initiative. I recommend you, keep an eye out for the synthesis report when it's released, hopefully sometime this week. Thanks.

Heather Field:

Fantastic. Thank you, Acacia, for that very comprehensive analysis of some of the changes we're seeing and what that impact is on rainfall across the state. What we thought we would do today is, we've heard from Acacia, we thought then we'd get an impact or get some thoughts from a couple of people in the industry, in agriculture, and see what these changes are actually doing and causing at a farm scale and what that means in terms of managing and farm practices.

Heather Field:

We've invited Lyndon. I'm just going to transfer some control over to Lyndon so he can pop up some slides. Lyndon is joining us from Agriculture Victoria. He's a sheep officer and also has a family farm and runs a sheep business in central Victoria, just at Shepparton. Today, Lyndon is going to share what they've implemented on their farm to manage increased seasonal variability and what this means for their sheep properties. Over to you, Lyndon. You just need to unmute yourself. I'll unmute you.

Heather Field:

Now, we can't hear you, Lyndon. I'm not sure why we can't hear you yet, just unmute. Unfortunately, we're not hearing you, Lyndon. I'm not sure why. We heard you on there before unless you've changed something with your speaker.

Acacia Pepler:

It might be worth just unplugging and replugging in the headphones. It's just not behaving, is it?

Heather Field:

No. Well, we'll give, Lyndon, half a minute, otherwise, we'll pass over to Dale while we sort out Lyndon's technology.

Dale Grey:

I think my microphone is working.

Heather Field:

All right. Well, we might just pass out to you, Dale, as we're working in the background to get Lyndon's audio working again. Thanks, Dale. I should introduce Dale. Most of you do know Dale. Dale is based in Bendigo and have been working with Agriculture Victoria for about 25 years and comes from a cropping farm in Meatian in Southeast Mallee. He comes from-

Dale Grey:

Meatian.

Heather Field:

What was that?

Dale Grey:

Meatian is the pronunciation.

Heather Field:

Sorry about that. He tries to maintain his agronomic skills while specializing in climate and weather for the last 12 years and is the editor of the Break suite of climate newsletters and YouTube videos. Over to you, Dale.

Dale Grey:

Thanks, Heather. I've been thinking about what I'd say for the talk today and upon listening to Acacia's talk there, well, it's been apparent for a while, I think, but it is clearly apparent that farmers have been adapting to these changes for a number of decades at least the last 10 years because they've had to. The first one of those is summer moisture. Summer retain moisture for crops has always been important in low rainfall districts.

Dale Grey:

We see that, because people used to cultivate, they used to fellow paddocks for long periods of time mainly to keep the weeds off them and to store moisture away for the coming crop and that had worked very well. But what we've seen in recent times has been a swing away from cultivation and more to direct drilling and stubble retention and the way control has come from chemical sprays over summer to killer weeds. That has proved to be an amazingly good tactic to store the moisture away over summer and leave it for the crop as an insurance policy in case the spring or the winter is a bit dodgy.

Dale Grey:

That practice has been going on pretty commonly now for at least the last 15 years. I think we'll only get to see more of it. What's interesting is how we will almost certainly, I think, see this practice move Southwards and Eastwards. It certainly works well in dry areas, less than 400 millimeters. But when you're around that 500 millimeter mark, historically, you wouldn't have considered doing this because you would get enough rainfall in winter. It would often get wet in winter and this is the problem.

Dale Grey:

If you're storing moisture and your profile is half full before the start of the year, in the higher rainfall environments, it's almost certainly going to get wet in winter and cause issues. So we don't see these in high rainfall areas. In fact, they are often trying to water paddocks during summer so that they start the season with an empty profile because it nearly always fills up.

Dale Grey:

But particularly, with that dry winter, initially it was counting points, a lot of people had soil moisture, they were feeling worried about the season. We, fortunately or not, got a very dry winter such that, that soil moisture was used by a lot of crops this year as a result of the stuff that was stored over summer and managed to allow us to ride out a dry winter.

Dale Grey:

There's often talk about summer crops, I'm quite ambivalent about those. The problem I see for them is that, our evaporation rates are very high in summer and the rainfall rate is generally too low. I've physically ground some summer crops on trials over the summers of 2011 and 2012 which were the two wettest ones for a long time. Absolutely, you could grow summer crop there. I had sorghum way over my head that year. But who was to really know that, that might happen?

Dale Grey:

A lot of the time it tends to be more opportunistic. People see a rainfall event and they bang something in. Usually, it's the stock feed. Maybe Lyndon might talk a bit about what he thinks about summer crops as well. But certainly, when it comes to actual grain crops, things like safflower and sunflowers historically used to get a bit of a go. We sowed a couple of safflower crops yesterday in Northern Victoria. And even though they probably got sowed on a full profile, they're not looking too good at the moment just because it just doesn't take very long of dry weather to use their full profile.

Dale Grey:

A full profile in November would lost a month because we don't have the soil profile that places like Queensland and stuff has. I think it's best suited if you've had a full paddock, in particular, a wet paddock from a wet winter or something and you can sow something in spring and get a bit of a salvage operation out of that. But the whole problem with summer crops also, people in the drier rainfall areas, they're going to be using valuable stored soil moisture and nutrients that you probably want to be keeping for the coming season.

Dale Grey:

As we get to sowing, I think that's where we've seen the real impacts of what Acacia was talking about. Seasonal break this year was fantastic, but in many of the 15 years, we're getting breaks that just limp across the line with low rainfall events that add up. The seasonal break has not been so defined. Because of that, it's been really important to get a crop in and out of the ground as quickly as possible. Modern direct drilling and stubble retention has, in fact, allowed that.

Dale Grey:

What I think is perhaps interesting about this work and perhaps just in general, again it's really important that if you get rain, what we'd call out of season in March, consider sowing something, consider getting something in the ground. The Birchip cropping group work showed that it rarely died before winter. Sand is the best. It did die one year on a heavier ground. I think that the interesting thing about sand is that it works really well with low rainfall events, the crop gets everything.

Dale Grey:

So consider planting something if you've got rain in March. I'm reminded of the work that Robinson did out of the Mallee with his storm chasers programs 10 or 15 years ago. He planted all sorts of crops in March that you wouldn't think he'd normally do and he always got a yield and it was very rarely worse than the stuff that was planted at the right time.

Dale Grey:

The other thing we've seen is just the huge swing into dry sowing. If it hasn't rained by April, most people are sowing something dry. That was once deemed incredibly risky and now it's deemed essential. Mainly from the scale of farms, because they need to sow everything at the right time or close to the right time, one thing that drives sowing dry is it sets you up for the highest yield potential possible for that year because as soon as it does rain, your crop comes out of the ground. You'd have to then sow it.

Dale Grey:

The problem with it is, it optimizes the weed competition, all your weeds come up at the same time. So it's very harsh in crop herbicide use as a result of dry sowing. But people are voting with their feet. There are people now who are quite happy to almost sow their whole farm dry, without rain. And the risks of that have been really low.

Dale Grey:

There's been few incidents of raining heavily and blowing up and failing or getting dodgy germinations. Things, if they actually germinate in autumn when things are cooler tend to stay alive a very long time before they actually fall and die. As long as eventually it does rain, it's amazing how crops particularly, all of which people thought were dead and buried and gone, when it's finally rained enough in June or July, they actually come up.

Dale Grey:

It's been critical to plant everything as quick as possible while moisture is optimal. Because of that frontal rain not coming as frequently, the opportunity to get enough moisture at planting is being decreased. So it's been critical to get the crop in as quick as possible while the moisture is good as it can be.

Dale Grey:

The other thing is that, barley is a really tough crop compared to all the other cereals. It has early maturing, it fills grain at higher temperatures more so than wheat, better, and it's got two degrees better frost tolerance. What we see in the last few years I think is, people choosing barley over wheat just because of it's physical toughness. In the future, I think we're going to demand tougher crops that are actually able to cope with tougher conditions, and barley is certainly one of those.

Dale Grey:

The other problem we have is things like weed strategies. We have a weed strategy called a double-knock that we use where the opening rains come, we spray weeds out and instead of selling immediately, we wait for another germination of weeds and kill that. That's a really good herbicide resistance strategy, but they're quite problematic if you're not getting decent breaks, particularly early ones.

Dale Grey:

I've seen instances where people who are waiting for double-knocks have had to wait until June to get their crop in the ground because that second rain just never happened. That's something to keep in mind if you're contemplating that. There are certain years, I think, and this year was one of them, where they are better suited. During the season, we have nitrogen applications.

Dale Grey:

Well, in next 10 or more years or in a lot few time, we've started to go more technical. We've not put nitrogen up front, we've tended to wait to see what the season did and to wait for the those 10 mil rainfall events to get nitrogen on. But more and more, particularly in our drier environments, we're noticing or seeing that those opportunities are few and far between. In a year like this year, particularly in the Mallee, if you waited to put nitrogen on for that event, it eventually went on too light and narrowed the amount of time it was available for your crop to take up that nitrogen.

Dale Grey:

I think we're probably going to see a swing to nitrogen going on earlier mainly because, particularly if high is an option for you, there's been no downside. If you've grown dry matter and the season has failed where you cut more high as a result of putting the nitrogen on, if you don't choose to cut high, the nitrogen is not lost to the system, it's just delayed perhaps to the following year.

Dale Grey:

The other thing we've seen people doing extensively is changing to a proportion of their crop being what I call a multipurpose crop. Something that you put in and you suck it and see it as a bit of spring insurance as to what might happen. The predominance we see of people growing vetch in Victoria's Wimmera Mallee is a big reason for that because it has both grazing, green and brown manure, high-end grain option. It's a really true multipurpose crop and it's putting some nitrogen back in the ground, which is an amazing bonus as well too.

Dale Grey:

We could grow things like dual purpose crops like oats and cereals for grain and grazing as well but they don't quite have that flexibility that vetch does. I think people have voted with their feet there to putting a crop in the ground that is a bit bombproof depending on what the spring does. It gives them flexibility. I think we're going to be looking more and more at crops that can have more than one purpose.

Dale Grey:

The last thing I'm going to talk about, Heather, is just harvest. We see that thunderstormy rain increasing in harvest. I get the feeling this is going on. We've had wet harvest with rain quite a bit. It's always been important to get the crop off as quick as possible but I think it's becoming more and more important and to utilize all the storage options that are available on your farm. We see people using things like temporary silo bag storage as well just as harvest logistics to get crop under cover as soon as it's been harvested.

Dale Grey:

I think in terms of breeding, we're going to have to see more importance. We've seen high importance but on weather tolerance. Actually, having our crops that can cope with a bit of rainfall before they're damaged to become only stock feed options rather than usable for brewing and milling purposes. We've been keeping stubble cover, that's been a very common thing. I think what we're going to see is more of that happen once again further south and further eastwards as the rainfall keeps drying out and the temperature increases.

Dale Grey:

People do it, I think, for summer. That might help the evaporation over summer. Generally, the sum always wins over summer. I think stubble has its greatest advantages in autumn because it actually increases and leaves the moisture there for getting a crop in the ground and getting it out of the ground longer reducing evaporation in autumn rather than in summer. That was the main points I wanted to make, Heather. I'm not sure if Lyndon is back on with the sound now but I'm happy to flip over to him now.

Heather Field:

Great. Thanks, Dale. Thanks for sharing those insights on what this means for croppers and how they are managing these changing conditions. That's been great. We will see if we can get Lyndon.

Lyndon Kubeil:

Heather, can you hear me now?

Heather Field:

We can hear you, Lyndon.

Dale Grey:

We can.

Lyndon Kubeil:

Fantastic.

Heather Field:

I'll just pass over control. Hopefully, that doesn't change the volume. If you can bring up your slides. Excellent.

Lyndon Kubeil:

In the process.

Heather Field:

Great, we can see that. Thanks, Lyndon. Over to you.

Lyndon Kubeil:

Excellent. Thanks, Heather. Sorry guys for the technical problems early on. When Heather asked me to talk about on farm adaptation to seasonal variation, I thought the most practical way I can do it is to talk about my own experiences so what we do on our farm and some of the things that we've changed since we purchased in 1999. I was glad to hear Dale use the word flexibility. You'll probably hear it a lot in mine and you'll probably understand why shortly.

Lyndon Kubeil:

But just a really quick background about our farm, I'm going to use it today to make it real, I suppose, in some of those adaptations. We purchased our farm in 1999. It's not a great big farm. It's 700 acres. It's a creek flat country with the Phalaris sub clover base, loam and clay land soils on about a 550 mil rainfall. We run about 12 to 14 DSE per hectare. And we join about between 1,300 and 1,500 Merino annual use. You'll find out shortly why that variation.

Lyndon Kubeil:

I'll just jump back to purchasing in 1999. We had 10 years of fairly solid seasons post 1999 so it really made us think about risk. When you purchase a farm, obviously, you got high levels of debt and with higher levels of debt comes more exposure to risk. So we wanted to sit down and we thought the two types of risks that we identified as being our biggest issues were market risk and I grew up as a boy on a wool growing property so I certainly understand the issues around the wool market and price risks.

Lyndon Kubeil:

But today, we really wanted to address the seasonal risk issue. I can't seem to get rid of that. The things that we identified were short springs and light autumns were two big ones. In our country, we also have to manage flooding.

Heather Field:

If you can remove that little gray box or that box across to your other screen-

Lyndon Kubeil:

All right, Heather, if I could. If you can help me with how that might happen.

Heather Field:

Maybe flip to the next slide and it may make it easier.

Lyndon Kubeil:

Right in the middle of my beautiful...

Heather Field:

I'm sure if we've lost connection there with Lyndon.

Speaker 1:

We're having all of the technology problems today. It's a good time to remind everyone, if you have a question, check in the chat box, address it to all panelists. And at the very least, we'll have Acacia and Dale and hopefully we'll have Lyndon as well. Just give him another couple of minutes. But maybe if we've got some questions sitting there, Heather, it might be good time.

Heather Field:

Yeah, I think we might pop to a question while we're just waiting on Lyndon to join us back again. We do have one I think for Acacia and she wanted to know, does the sea surface temperatures of the Tasman Sea off the coast of East Gippsland in southern New South Wales influence the intensity and behavior of our East coast lows?

Acacia Pepler:

That's a great question. Unfortunately, the answer is complicated because, the two ways that we've tried looking at this in the past. This is one of the things I was interested in my PhD so I'm the right person. East coast lows are influenced by a lot of different things. If you try to do an index of how warm the Tasman Sea and correlate it with your likelihood of having an East Coast low, there's no real relationship because there's so many other things going on.

Acacia Pepler:

But we have found that, when we run model simulations similar to weather forecast or even prediction type works over a long period of time, if we change the sea surface temperatures in the East, we find that we get more smaller cyclones and more cyclones overall if we have warmer sea surface temperatures but it doesn't necessarily affect those really big systems that are sitting well up into the upper atmosphere that are the most important.

Acacia Pepler:

So warmer sea surface temperatures do seem to play a role so we do expect that the projected future warming in East Australian current could make it easier for us to get certain types of East coast lows near the coast. But, to our surprise, it turned out to be a relatively minor influence in the scheme of things and it didn't seem to make as much of an impact on those really big coast lows as we thought it would.

Heather Field:

Thanks, Acacia. We'll continue with a couple of more questions while we wait to see if we can get Lyndon back on. Another question for you, Acacia, from Graham Anderson, great presentation and analysis. I reckon high winds that have been impacting some areas and he's just wondering if you know of any analysis on the issues of wind in Victoria that's changing at all.

Acacia Pepler:

Wind is another thing that's really complex because, observations of wind can be quite local. We've only got so many wind observation stations and those changes how they measure wind over time. So it's actually really hard to say anything about observed changes in wind. In fact, there's some evidence out there that suggests that overall, there might be even be a decrease in wind types of Australia.

Acacia Pepler:

However, I can tell you that, we have a project as part of the energy sector climate information so we've been working very closely with IMO and other agencies to try to understand some of the influences that are very important for things like power generation. There's a lot of work going on at the moment trying to, just like how I showed you some environmental parameters favoring thunderstorms to look at the thunderstorms, they've been doing some very similar work trying to develop good diagnostics they can use to look at when periods of extreme winds are more likely.

Acacia Pepler:

That work is, I believe, currently under review. I don't know much about it because I'm not involved, but, Graham, I'm sure you know [inaudible 00:46:09] so you could probably send him an email and he might be able to give you some more information on that. Unfortunately, I can't give you an easy answer.

Heather Field:

Thanks, Acacia. It looks like we have lost Lyndon. I think he has had some internet issues so we'll continue with questions. If you have got any questions for either Acacia or Dale, do pop them in the chat box and we'll pose those to both of them. We do have a question about thunderstorms. Any comments around possible issues that increased thunderstorm rainfall might bring, for example, variable hit and miss within a district or across the farm and how farmers monitor or deal with this? The highlight might be take advantage of thunderstorm rains when they happen. Maybe over to you, Dale, for that one.

Dale Grey:

I think I'll look at that first, Heather. I'll put the video back on. There we go. Thunderstorms, they're a blessing or a curse depending on when they're happening, I suppose. The first thing that used to happen historically was, when we got a really high rainfall event in summer, it ran off our paddocks. Now, with modern stubble retention and better soil structure in most paddocks in cropping areas, we see the moisture that comes from thunderstorms going into the ground rather than running off.

Dale Grey:

I think that's probably still a challenge for a lot of grazing people that if they get some thunderstorm and their paddocks are too bare and don't have enough cover, it runs off. But the catch 22 of that is, if you have dams that rely on runoff, you might not be getting the runoff in winter and spring that you once got into those dams and then, a summer storm event that runs off quickly can fill dams in one event, not from a lot of rainfall, but just from a lot running off your catchment into the dam.

Dale Grey:

That can be critical to filling dams in places. But you wouldn't want to be relying on it, Heather. That is the dilemma. But the variability of thunderstorms over farms, look, we see that. People report that all the time because they've got rain gauges around, one in separate farms and they're reading completely different things. One of our farms this year is yielding much better because it got 30 to 40 mil at the start of the season more than three, four kilometers away.

Dale Grey:

I think really, if you don't measure it, you can't manage it. I think people have seen these effects in the past but without any data towards the actual rainforest that fell, they've got no idea really why those variations of yield perhaps have happened. They saw that thunderstorm occur and we're in it. So we get variations of rainfall, but I think we see the time. I think there's a few more people putting out weather stations into their farm with perhaps just a few more manual rain gauges, I think, scattered around, they might give us a bit of feeling for the distribution of rainfall.

Dale Grey:

Which in thunderstorms, I think we see it in the decrease in the frontal and low pressure rainfall through winter, the old concept of a general rain where the whole district got 10 mil, now seems to be quite a joke, it just doesn't seem to happen. Even now someone is getting five and someone's getting 15.

Heather Field:

Thanks, Dale. Any any comments from you Acacia on that question?

Acacia Pepler:

I'm afraid. Well, I'm from a dairy farming country in New Zealand. My grandparents are front side in orchard. My knowledge about farming is pretty limited so I'll leave it to the experts like Dale.

Heather Field:

No worries at all. We do have a question on predictability of variable events. How is forecasting coping and keeping up with changing rainfall amounts, thinking of recent examples where we've had 10 millimeters predicted but got 30 millimeters and vice versa?

Acacia Pepler:

In the weather forecasting context, we're constantly working to improve the models that we use. I'm not in that part of the Bureau, but there's always a lot of work to make the models better. One of the many aspects that we're working on a lot over the next five to 10 years, is doing a lot more use of ensembles. That means, instead of just running with a model once at a really high resolution, at the same time, you can run maybe some slightly lower resolution models but run it 20 times at slightly different initial conditions to help us get a much better idea of the range of likely outcomes.

Acacia Pepler:

This is a really cool early studies they've done on some of these events showing that, if you average all the systems together, you get a broad pattern, but you can also highlight, oh, these areas that some of the models say you might have heavy rainfall. We're doing our best. We're working on improving the nowcasting results, working on trying to get better at forecasting the next few hours of rainfall based on what we can see on the radar.

Acacia Pepler:

The forecasters are doing an amazing job of what they can do but in the end, there's a reason why when we produce rainfall forecast we always give you that rainfall range. That only covers a small proportion of the range of all of the outcome. So we try to give as much information as you can about the range of outcomes but in the end, weather is random so unfortunately, I don't know if we'll ever be at a point where we'll be able to say, this farm is going to get a thunderstorm and that other farm 10 kilometers away isn't because it's very high resolution. It's a really tricky problem, especially with these thunderstorm-related rainfall which can pop up anywhere.

Dale Grey:

Acacia would be well aware, of course, that the warmer the atmosphere is, the more moisture it can hold. If you look at rainfall events historically, you know you always get those really heavy rainfall events in summer because the air is warmer. You don't normally get really heavy rainfall events in winter. That extreme variability is towards the summer end because the air is physically warmer. As springs are warmer as well, the potential is there to hold more rainfall and that tends to fall out in thunderstorms at that time of the year which as Acacia said, we know they're going to happen, but it's pretty difficult to know where they're going to land.

Heather Field:

Absolutely. We have a comment and a big challenge for cropping in more marginal areas and sloping land where we continue to see severe soil erosion during more intense rainfall events.

Dale Grey:

It's all about cover, Heather, that's right. If it's sloping and running off, there's simply not enough cover on the paddy to slow it down. Of course, slopes are affected too. If you've in a hilly country, it wouldn't matter what cover your head on, it's going to go off. But I'm more familiar with the flatter country where I'm from, where if it's coming off, it's clearly an issue of not enough cover.

Heather Field:

Let's go to one final question before we do finish up. That's for forecasters. Does thunderstorms create more uncertainty in how much rain a farm might get?

Acacia Pepler:

I suspect so but I can't answer on behalf of forecasters. But given that we know thunderstorms are more spatially variable, it makes sense that if you're getting more of your rainfall from thunderstorms, then you're more likely to have patchy rainfall from area to area.

Dale Grey:

Which probably comes to my point earlier, Acacia, that if it is falling more randomly across your farm, you probably need to have some measurement of that variability. And then, you might be able to change your management if you know one area hasn't got rain and one has. But unless there's a measurement of that, it becomes a bit more difficult.

Dale Grey:

I know some of the radars are rival to actually show a much better pattern of the intensity of the rainfall spatially so maybe there's an ability that we might be able to use that data to show what parts of our paddocks have got the greater lion's share of the rain out of the fronts coming through or the storm itself from those radar signals. But I've no idea how you go about doing that.

Acacia Pepler:

There's recently been upgrade to the radar that have been ongoing over the last while to provide new capabilities that makes the rainfall estimations... Because, radar isn't measuring rainfall, it's measuring its own fields that we then use algorithms to convert into rainfall. There's a lot of work going on that makes sense, especially from those radars and how we interpret that radars to make an estimation of rainfall and also we're trying to improve how we can integrate radar rainfall and other sources to provide this good understanding of what really happens.

Dale Grey:

It's really up to the event. You're really looking for that spatial distribution of where it fell, particularly when it comes at night, you're not looking, you can't see. Graham just pointed there's an explosion of weather stations out on farms. Now, I think that really is just showing the variability that actually is happening on farm. It's probably always been there, but what you're showing here, Acacia, is that it's increasing and it's probably likely to keep doing that. I noticed Lyndon is back.

Heather Field:

Yeah. Hello, Lyndon.

Lyndon Kubeil:

Hello. I delivered a whole presentation to myself.

Heather Field:

Well, we have got a few minutes left if you'd like to just summarize what you were going to talk about. We still have people online who would be keen to hear so please share for maybe five minutes.

Lyndon Kubeil:

Tell me where I got to before it dropped out.

Heather Field:

We didn't get very far past your second slide.

Lyndon Kubeil:

So we just talked a bit about risk, did we?

Heather Field:

Yes.

Lyndon Kubeil:

Okay. Well, I really wanted to focus on systems to manage seasonal risks. I wanted to talk a lot about short springs and failed autumns for the two things that I was going to address. I've been talking a lot about flexible farming systems and making sure that we're able to actually take advantage of good seasons and not just be completely focused on the poor seasons. I had a really lovely photo of 2016 with which Acacia talked about of Phalaris five foot high and an amazing amount of growth.

Lyndon Kubeil:

Water was something that we needed to address. We ran out of water in both 2003 and 2006 and quickly realized that we needed to do something better from a stockholder point of view. So we did some homework and I looked at both water catchments and desalination and we went down the desalination pathway. We had to go into deep water about 100 meters down which was quite salty and then put a desalination plant on. It's been absolutely brilliant ever since. It's got us out of trouble on many, many seasons.

Lyndon Kubeil:

Growing grass, just the importance of making sure that we optimize the moisture when we have it. Acacia talked a bit about reducing winter rainfall. We need to make sure that we're as efficient as possible at utilizing winter rainfall while we have it. Our policy is to do lots of soil testing. We soil test every paddock every second or third year to make sure that we're addressing those deficiencies and optimizing the moisture use.

Lyndon Kubeil:

Stock containment, for the obvious reasons, we use stock containment for minimizing topsoil loss, maintaining ground cover, maintaining planarity in our pastures. Probably from a least obvious point of view, we use every autumn to make sure that we're managing our leaf area going into winter. So by optimizing our leaf area going into winter, we can optimize our winter growth rates and again optimize the soil moisture use.

Lyndon Kubeil:

And then, if we can grow some reasonable amounts of winter feed, even if the season does fall short in spring, we've generally got sheep in good condition and they're saleable autumn. I had some photos of some temporary electric fencing that we actually use for some containment areas. I do have some permanent setups though I am also prepared to just use electric fencing across the corner of a paddock with a shade and water. Electric fencing has been a fantastic tool for us.

Lyndon Kubeil:

But the biggest adaptations that we've made are really in the space of genetics. So we've gone from growing up in a Merino system where we tended to want to put more and more wool on to our sheep and they probably weren't ideal for coping when things got to be tough. We've put a lot of emphasis in the last 18 years on growth fat and muscle in our Merinos. That's really built a resilient ewe which can carry more fat and muscle and obviously handle a much tougher environment.

Lyndon Kubeil:

Fertility has been the big game changer with those use. They scan very similar to a crossbred you. The Merino is between 160% and 170%, maidens included. Fertility is a game changer when it comes to flexibility in a farm system. The ability to restock faster after having to reduce stocking rate, increasing sales stocking numbers and the ability to join more to a terminal or maternal which also provides more flexibility in your system.

Lyndon Kubeil:

The other big one is early maturing Merino use that we can now join at seven months of age. So if we have had to do stocks, again, we can use those to ramp up their numbers much faster than we would have been able to in the past. That's probably the key things, Heather. I did have lots of pretty pictures to show and I'm sorry that the technology didn't work for us but that'll do it.

Heather Field:

Thanks. Thanks for persisting and coming back on and at least sharing some of your insights. What we might do, we might try and run another one in the new year so you can better share your story and how you're managing seasonal risk. Thank you and thank you to our participants who have stayed online to hear Lyndon's short summary at the end there.

Heather Field:

We did have 150 people register for today's webinar and we had about 70 online for the most of it. So I just want to, again, thank our presenters, Acacia, Dale and Lyndon and everyone for your questions and participation today. This is our last webinar for 2020. We are in the planning stages for continuing our climate webinar series in the new year.

Heather Field:

So if you do have any suggestions and ideas of presenters or topics you would like to hear about, please email us at climate.webinars@agriculture.vic.gov.au. and we'll take those on board and plan a good series for the new year. Everyone who has registered today will receive a recording of the webinar so please feel free to share that. Thanks again everyone and thanks for hanging in there with our few technical issues today. Have a good afternoon.

Page last updated: 16 Jun 2021