Climate in-brief

 
  • An active MJO in phases 5-6 north of Australia has brought moisture to central and eastern parts of Australia in the past week;

  • Multi-week models are favouring rain across eastern areas of NSW and Qld with another change expected through the mid-latitudes around mid-November;

  • Seasonal models have wound back previously bullish probabilities for the coming three months, however, the majority of models are in agreement for wet conditions none-the-less; and

  • Analysis - La Nina 2020-21: how does it compare to other events in the past?

The chart above shows humidity well above normal down the centre and eastern area of Australia at 3pm yesterday.

The chart above shows humidity well above normal down the centre and eastern area of Australia at 3pm yesterday.

Australian weekly rainfall and relative landscape water balance

An active MJO has triggered some tropical moisture and rainfall to the centre and eastern parts of Australia. http://www.bom.gov.au/jsp/awap/rain/

An active MJO has triggered some tropical moisture and rainfall to the centre and eastern parts of Australia. http://www.bom.gov.au/jsp/awap/rain/

Water balance anomaly shows a dry WA and parts of CQ and eastern tropics.Australian relative landscape water balance ‘upper soil’ courtesy BOM

Water balance anomaly shows a dry WA and parts of CQ and eastern tropics.

Australian relative landscape water balance ‘upper soil’ courtesy BOM

Climate drivers

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With the La Niña now old news the story of the last fortnight is the cooling of the eastern Indian Ocean, bringing the IOD back more towards neutral, which is unlikely to affect the climate to years end. The SAM is a key ingredient for moisture into NSW and Qld, and this is not behaving as models predicted. Normally the SAM follows suit into wetter or positive phase, but the last few months only gets a rush and retreats back to neutral or negative phase. One to watch this harvest for sure.

What to know about the climate drivers and how they are measured? Click here

Multi-week model survey (8-28 days)

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A busy 2-3 weeks ahead for most areas with southern and eastern regions set to capture more of the moisture during the current MJO event, which is currently active over Australia in phase 5-6. When the MJO moves into the Western Pacific in November, gaps appear with fine weather returning for grain harvest in NSW and S Qld.

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Model form: the rather cautious IRI model is more bullish for NSW and showing a dry signal for the tropics in the coming weeks. The JMA is optimistic for Qld earlier in the month and NSW later in November. The BOMs ACCESS S and ECMWF seem to have the rose coloured glasses on throughout the next three weeks and should be taken with a grain of salt. Keep an eye on the Meteologix 10 day Forecast XL as events draw closer for your area: https://meteologix.com/au

Analysis - 2020 La Niña: a closer look

Scientists around the world are busy reporting on the strength of the current La Niña. This is generally measured as the extent of the cooling in the Niño SST regions in the Tropical Pacific. Together with the trade winds and Walker Circulation (SOI), the stronger the La Niña, the moisture theoretically shifts towards Australia. A comparison of 2010 (a record strength event) ocean temperatures in Mid-Oct v 2020 shows a few notable differences; a cooler Coral Sea and cooler Arafura Sea (circled in red) to the north of Australia. These are important regions for convective moisture for weather systems and while cool now, will be watched with interest following basin-wide warming of the Indian Ocean at the end of November.

Other global climate researchers also point out the nuances among La Niña events and the similarities between 2020 La Niña and those of 1983-84 and 1988-89 (Nov-Jan rainfall, bottom panel). Check your farm rainfall records for these summers:

  • 1983-84 La Niña: cooler waters through the Maritime Continent (Indonesia/Malaysia) saw the mid-latitudes achieve high decile rainfall through this period and less so through the northern tropics.

  • 1988-89 La Niña: this La Niña arrived earlier than the current 2020 La Niña and brought fantastic rains in winter/spring. Southern areas of the continent fared much better than Qld through the analysis period.

If 2020-21 La Niña is characterised by more tropical forcing (SSTs driving the climate to change from dry to wet) over the Indian Ocean than the Maritime Continent north of Australia, then some caution for much anticipated wet season rains through Qld would be prudent. Close monitoring of the phase of the SAM (NSW and s Qld) and MJO activity will be critical in the following months.

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Monitoring the SAM

Recent research by Hendon et al, (2014) at the Centre for Australian Weather and Climate Research found the Southern Annular Mode to be the leading mode of circulation variability through parts of inland eastern Australia where cotton is grown; particularly in the spring planting period.
 
A positive SAM has been proven to increase moisture supply into fronts and troughs forming in eastern Australia. The chart provided by Climate Prediction Center (US) shows the most recent observations of the SAM or (AAO). 

A negative SAM traditionally leads to a dry westerly circulation pattern through eastern Australian cropping areas.
 
BOM researchers Lim and Hendon (2013) found the SAM has the strongest connection with El-Niño Southern Oscillation in October and November – whereby the SAM is influenced most by El Niño or La Niña conditions.

Growers and advisors are encouraged to monitor the phases of the SAM together with seasonal forecasting, multi-week and short term weather models during planting. A short cartoon explaining the SAM can be found HERE

The SAM has had a burst of exuberance into positive phase in early October and has not settled there as predicted, rather is tracking along in neutral. While 2010 has become a legendary benchmark La Niña year, it must be remembered that a record positive SAM has been found to be a large contributor to onshore flow and increased rainfall in that year (Lim et. al. 2016).



Antarctic Oscillation or SAM observations below (23 Oct)

http://www.bom.gov.au/climate/model-summary/#tabs=Indian-Ocean

http://www.bom.gov.au/climate/model-summary/#tabs=Indian-Ocean

Weather Live

Cost:           $6.49 AUD / week

$40.99 AUD / year

You can download this app for free, and there is a 3 day Free trial period, however it is essentially a paid app (which does mean there are no pesky ads).

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Features:     Visually appealing and easy to navigate, this app has some handy features. The usual inclusions of current weather conditions (with the ability to add a list of set locations), forecasts temperatures & wind and weather alerts or warnings. The options of changing layouts etc.

My favourite feature of the app was the forecast rain maps. With location settings on, your location is marked with a dot on the map. The third image (and the blue dot) suggests our headers are not going to get back into the paddock today :-(

If you’re all about your Apple Watch®, this app has been designed for it.

Overall:        This would be my preferred weather app so far, so I will continue to pay unless I find a better one.

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Chart of the Week - water vapour approaching

The water vapor content of the atmosphere is of critical importance to nearly every facet of atmospheric science. Observing the processes that determine the water vapor content of the atmosphere is, therefore, of fundamental importance. As the earth’s surface is the source of most atmospheric water vapor, observations of vertical turbulent transport of water vapor in the planetary boundary layer have been the subject of many research projects. Evapotranspiration can vary significantly across the earth’s surface due, for example, to variability in insolation, vegetation cover, soil properties, and precipitation. Area-averaged water vapor flux measurements are necessary to get a large-scale view of surface–atmosphere interactions. 

The Extreme Forecasting Index (EFI) is an integral measure of the difference between the ensemble forecast (ENS) distribution and the model climate (M-climate) distribution. This allows the abnormality of the forecast weather situation to be assessed without defining specific (space- and time-dependant) thresholds. The EFI takes values from -1 to +1. If all the ensemble members forecast values above the M-climate maximum, EFI = +1; if they all forecast values below the M-climate minimum, EFI = -1. Experience suggests that EFI magnitudes of 0.5 - 0.8 (irrespective of sign) can be generally regarded as signifying that "unusual" weather is likely whilst magnitudes above 0.8 usually signify that "very unusual" weather is likely. Although larger EFI values indicate that an extreme event is more likely, the values do not represent probabilities as such. 

What does this mean? The prediction for excess water vapour and the presence of an “atmospheric river” will grace eastern Australia this weekend, and is classified as an unusual and extreme event, in areas shaded red (image courtesy ECMWF).

Farmer climate focus - Sam Becker, Jarrah Cattle Company

 

Jarrah Cattle Company’s Sam Becker runs a livestock business that includes some forage cropping. The climate and managing groundcover to ensure feed budgets are met, provides the greatest challenge for management.

 
Banana, QLD
Sam i.jpg

Sam Becker

Banana, Qld

Location snapshot

Catchment:   Lower Fitzroy Catchment

Altitude:        181 m

Enterprise:    Stud Hereford, Redford and Jarrah Red cattle and forage cropping, including sorghum and oats.

Rainfall:        Wet season (Oct-Mar): 78% rainfall
Cool season (Apr-Sep): 22% rainfall

Seasonal rainfall climate drivers: Banana, Qld

El Nino-Southern Oscillation (ENSO) is the key climate driver, however, ENSO impacts are very weak post-January to May.

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What are your ‘go-to’ sources of climate/weather information?

BOM is a big one and we also use The Long Paddock reports supplied by DAF which allows us to see which percentiles we’re sitting in and how much groundcover we have. We also link that in with our records of past rainfall and then looking at the future rainfall as well. I also get a fair bit of information about climate change from social media to be completely honest and then when you read stuff about that and then look at your past three to five year annual rainfall, for example, we’ve been below our annual rainfall for the last five years, so, it’s looking at that to try and find trends. It’s more to find those trends to manage how heavily we stock and where we stock.

How do you consider climate in your farm management?

A big thing we do is try and link our groundcover and rainfall and look at those two things to see if we should be buying or reducing stock. That’s probably been reactive to an extent, but we have also been making decisions on the go, I guess that sort of reflects the decisions that we have made. We don’t want to start with nothing. We want to have groundcover when we go into the wet season and make sure there’s a bit of a body of feed. If there’s nothing there we would have sold. We try to de-stock before we get to that stage, or at least we keep selling off dry cattle to spread our breeders around so that we keep some level of groundcover there.

Can you share a climate success (or failure) story with us?

Probably a failure. In the last five years we were too reactive to the climate. We were selling down, but we probably weren’t doing it quick enough, so we did– particularly with one property – eat it to the ground. We sort of got trapped when the cattle became out of spec, so they became hard sell. We were definitely reactive to that. We had a set number in our heads that we knew our properties could run and we didn’t take into account the last five years with below average rainfall and then the last two which were significantly below. We still, in our minds, thought that we could run a certain amount of cattle which, in turn, lead to one property significantly suffering.  

What’s your soil moisture looking like at the moment?

We’re pretty dry, as in we have had hardly any rain to date since April. So, yes, we are very dry. Not much moisture, not much protein in the soil, we do have a good grass-cover but it’s all dry feed. Because of this we are supplementing our breeding cattle with a fair bit a custom-mix dry lick that is made with our deficiencies and our country in mind.

Do you have altered management plans for the rest of the year considering La Nina has been announced?

We are definitely considering it. It’s now when we consider these trigger points we have that prompt us, depending on how much feed we’ve got, to start selling off dry cattle. This is so we can spread our breeders around so that we keep that good body of feed and then wait until rain comes before we increase our numbers. We’ve made a big effort this year to make sure we start off with good ground cover for the wet season. We definitely aren’t going to start buying in cattle thinking we are going to get good rain, we are going to wait until we’ve had decent rain, the grass has got away and then we would look to build our numbers again.

Have a farming climate story to share? Please contact us.

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The co-efficient of variation (CoV) for rainfall helps understand which months are more reliable than others. The chart shows a generally reliable monsoon rainfall, with November as the most reliable month and July as the least reliable month.

 

El Niño-Southern Oscillation is the major climate driver in the region. An analysis of Oct-Jan rainfall shows some broad trends towards average or better in La Niña years, low rainfall years in most El Niño years and neutral years as completely random.

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Developed by the International centre for applied climate sciences https://climateapp.net.au/ has some handy tools to understand the climate for your area.

A summer-dominant rainfall at Banana, Qld.  An output of https://climateapp.net.au/

A summer-dominant rainfall at Banana, Qld. An output of https://climateapp.net.au/

Tracking close to average rainfall for 2020. An output of https://climateapp.net.au/

Tracking close to average rainfall for 2020. An output of https://climateapp.net.au/