Monitoring the SAM

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The SAM has been strongly positive through June, pushing moisture into eastern Australian productive agricultural areas. The guidance below expects the SAM to retreat back into neutral levels, so it looks unlikely to influence our climate in the next fortnight at least.

Now we are in winter its time to start monitoring the SAM again. When the SAM is negative, winds from Antarctica blow further north up into southern Australia. When the SAM is positive, these winds pull back towards Antarctica, allowing moisture from the tropics to push into Qld and NSW. The SAMs main influence is in spring and summer, but it is worth keeping an eye on to help us ground-truth model guidance when we see a change. A really good video at the bottom of this article will help explain this a little better.

Antarctic Oscillation or SAM values (2 July)

 
 

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. 

Farmer Forecast - Tool of the week

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Wasting time with water and chemical logistics, trying to spray fallows and crops and battling high winds - or simply looking to fly a kite?

The BOMs wind modelling forecast can help plan ahead out to 7 days.

The outputs are broken into 6-hourly intervals. Click on the link below to plan your spray (or kite-flying!) week:

http://www.bom.gov.au/watl/wind/forecast.shtml

BOMs wind modelling forecast tool

Monitoring the SAM

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Now we are in winter its time to start monitoring the SAM again. When the SAM is negative, winds from Antarctica blow further north up into southern Australia. When the SAM is positive, these winds pull back towards Antarctica, allowing moisture from the tropics to push into Qld and NSW. The SAMs main influence is in spring and summer, but it is worth keeping an eye on to help us ground truth model guidance when we see a change. A really good video at the bottom of this article will help explain this a little better.

The latest values show the SAM around neutral and moving into positive phase (red arrows) which you would anticipate circulating moisture into central eastern areas, although the SAMs impact is only weak during early winter.

Antarctic Oscillation or SAM values (4 June)

 
 

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. 

Tracking atmospheric water vapour (Sun - Wed)

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This is pretty rare. Water vapour levels are in the extreme range basically all week. The image below shows a concentration of water vapour over central-eastern Australia for the period Sunday through Wednesday.

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. 

Tracking atmospheric water vapour (Sat-Sun)

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The prediction for extreme water vapour levels shows a concentration over the mid-latitudes over the weekend, where moisture is streaming across from NW Australia.

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. 

Monitoring the SAM

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The SAM is fairly stable in positive (wet) phase at the moment and set to continue. The SAM is theoretically coming to the end of its seasonal influence and looks unlikely to be a strong driver in the coming fortnight.

Antarctic Oscillation or SAM values (26 Feb)

 
 

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. 

Monitoring the SAM

/

The SAM is fairly stable in positive (wet) phase at the moment and set to continue. A stronger positive surge of the SAM would certainly boost confidence for rainfall prospects in eastern areas of S Qld and NSW in the coming weeks. Its influence will be reduced once we move into March.

Antarctic Oscillation or SAM values (12 Feb)

 
 

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. 

Monitoring the SAM

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The SAM had a brief stint in negative/neutral zone but has since recovered and is trending towards wetter phase in the next fortnight. A stronger positive surge of the SAM would certainly boost confidence for rainfall prospects in eastern areas of S Qld and NSW in the coming weeks.

Antarctic Oscillation or SAM values (29 Jan)

 
 

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. 

Tracking atmospheric water vapour (Sat-Tue)

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The prediction for water vapour levels shows a concentration over north-west Australia, and surprisingly not showing up (as high levels) over SE Australia where rain is predicted for Monday-Tuesday.

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. 

Monitoring the SAM

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The SAM is set to dip into negative and then recover the around neutral levels. A stronger positive surge of the SAM would certainly boost confidence for rainfall prospects in areas such as the Darling Downs and Liverpool Plains this time of year. It looks unlikely the SAM will impact our climate in the coming weeks.

Antarctic Oscillation or SAM values (15 Jan)

 
 

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. 

Monitoring the SAM

/

The SAM continues in positive phase, which is great news for NSW and S Qld areas. The forecast (not displayed) shows the SAM being quite stable in a moderately positive zone. This will allow moisture flow into key eastern Australian agricultural areas. A strong positive surge of the SAM would certainly boost confidence for rainfall prospects in areas such as the Darling Downs and Liverpool Plains this time of year.

Antarctic Oscillation or SAM values (31 Dec)

 
 

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. 

Analysis - MJO: what is it and why do we watch it?

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The Madden-Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterised as an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days.

MJO Explainer

Click on the image to play this 3-minute MJO explainer

Click on the image to play this 3-minute MJO explainer

Predicting the MJO and where is it now?

Due to its slowly evolving nature, accurate prediction of the MJO is fundamentally related to scientists ability to monitor the feature and to assess its relative position and strength. Dynamical models generally do not predict the MJO well, partly because of the inherent difficulties that still remain regarding the correct mathematical treatment of tropical convective (rainfall) processes. Meteorologists use a variety of data and analysis techniques to monitor, study, and predict the formation and evolution of the MJO.

In the chart below;

  • The black line is observations with dates (where it is now is largest black dot #21)

  • The yellow lines are potential modelled outcomes (bracketed by shading)

  • The green line is the median prediction (where to next)

  • The phase is its location: Australia generally 5-6

  • The strength is indicated by where it is plotted: inside the circle = weak. Outside the circle = stronger. The closer to the outside, the stronger the pulse.

So what?

Dynamical models favour little to no MJO activity during Week-1 (22-29 Dec) but suggest potential renewed MJO activity over the Indian Ocean during Week-2 (30 Dec-6 Jan).

Given the current weak signal, the MJO is unlikely to substantially influence the tropical convective pattern or subsequent extratropical response. The ongoing La Niña remains the primary tropical convective driver (see the latest NCEP conditions report).

The weaker MJO may reduce tropical moisture but it has a silver lining - a strong MJO in phases 8-1 can bring on heat waves which we can do without!

Monitoring the SAM

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The SAM continues in positive phase, which is great news for NSW and Qld areas. The forecast shows the SAM being quite stable in a moderately positive zone. This will allow moisture flow into key eastern Australian agricultural areas. A strong positive surge of the SAM would certainly boost confidence for rainfall prospects in areas such as the Darling Downs and Liverpool Plains this time of year.

Antarctic Oscillation or SAM values (18 Dec)

 
 

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. 

Tracking atmospheric water vapour (Sat-Tue)

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The prediction for water vapour levels shows a concentration over northern NSW/S Qld and a large area in Australias NW, consistent with bullish rainfall prospects for those areas.

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. 

Analysis - Sea Surface Temperature Distributions 2010 v 2020 La Niña's

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December 2010 Sea Surface Temperatures and rainfall deciles

Record warm sea surface temps around Australia’s north and the Maritime Continent

Record warm sea surface temps around Australia’s north and the Maritime Continent

With the exception of a small strip, record rainfall through eastern Australia in that month

With the exception of a small strip, record rainfall through eastern Australia in that month

December 2020 Sea Surface Temperatures and rainfall outlook (21 Dec 2020 - 3 Jan 2021)

SSTs as of 11 December 2020 (tropicaltidbits.com)

SSTs as of 11 December 2020 (tropicaltidbits.com)

Fortnightly precipitation forecast 21 Dec-3 January 2020 (courtesy BOM 10 December).

Fortnightly precipitation forecast 21 Dec-3 January 2020 (courtesy BOM 10 December).

So what?

The La Niña signature can be clearly seen in both images, with cool water extending into the western Pacific Ocean. Models are anticipating the Coral Sea to warm and deliver rainfall to eastern Qld areas (although the latest 7-day change maps on tropicaltidbits.com would suggest otherwise). The waters around the Maritime Continent are not near as warm as 2010. The next research article suggests that we need these waters, and those to the east of Australia to be much warmer to supply rainfall events this summer - this warming may well happen in the next month or so.

Monitoring the SAM

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The SAM has bounced around a bit lately, but the outlook for the next 14-day period looks much more settled into a positive (wet) phase (above the dotted black line). This is good news and timely, with an approaching MJO.

Antarctic Oscillation or SAM values (4 Dec)

 
 

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. 

Chart of the Week - water vapour prediction (Sat-Tue)

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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. 

Let’s hope the high levels of atmospheric water vapour can flow through to precipitation in parched N NSW and S Qld areas (image courtesy ECMWF).

Monitoring the SAM

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The SAM has retreated into negative territory this week, although it is forecast to recover to neutral phase for the remainder of the month. Climatologists expect the SAM to become entrenched in positive phase through summer, in line with the La Nina signal. Until this occurs with some consistency, it is difficult for farmers in NSW and S Qld to get too optimistic with hopes for a fairytale wet La Niña summer.

Antarctic Oscillation or SAM values (20 Nov)

 
 

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. 

Analysis - stratospheric cooling over Antarctica: a closer look

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The Southern Annular Mode (SAM) index has finally broken through into positive phase over the last week, which could affect weather patterns in eastern Australia during the coming months.

The SAM is an index that measures the north-south displacement of a band of westerly winds flowing between Australia and Antarctica. 

When the SAM index is negative, these westerly winds move towards Australia and when it is positive, they contract towards Antarctica.

The positive phase of the SAM is linked to the stratospheric cooling over Antarctica, which made headlines last year for extreme warming (Left graph) relating to a negative SAM, not seen since the horrible drought year of 2002. The circle showed “çoupling” with the troposphere, which is where the SAM is measured and consequently, spent the rest of the year in a negative phase.

The second image (Right graph) shows the current - and very opposite situation. Stratospheric cooling has just “coupled” with the SAM, showing the cooling (blue) colours right through different heights of the atmosphere.

What does this mean? Stratospheric cooling (or warming) was found by Hendon et al (2020) to have a connection with the SAM. It’s anticipated that the SAM will be positive during La Niña, but this analysis does provide added confidence. A positive SAM occurs when the winds in the southern ocean contract (last image), allowing more tropical moisture to move south into the mid-latitudes increasing the chance of late spring and summer rain. SAM moving back into positive territory is a good sign for rainfall on summer pastures and crops from NSW through to the northern Darling Downs.

Want to learn more about SAM - watch this 2 minute youTube video

Spring 2019 - sudden stratospheric warming (top) and SAM (below). Last years event was the most extreme event not seen since 2002.

Spring 2019 - sudden stratospheric warming (top) and SAM (below). Last years event was the most extreme event not seen since 2002.

Current (Nov 2020) chart showing stratospheric cooling (top), coupling with a positive SAM (below).

Current (Nov 2020) chart showing stratospheric cooling (top), coupling with a positive SAM (below).

 
The winds in the Southern Ocean contract further south, enabling tropical La Niña moisture to reach the mid-latitudes.

The winds in the Southern Ocean contract further south, enabling tropical La Niña moisture to reach the mid-latitudes.

 

Monitoring heat waves this summer

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About heat waves

Heatwaves are calculated using the forecast maximum and minimum temperatures over the next three days, comparing this to actual temperatures over the previous thirty days, and then comparing these same three days to the 'normal' temperatures expected for that particular location. Using this calculation takes into account people's ability to adapt to the heat. For example, the same high temperature will be felt differently by residents in Moree compared to those in Orange, who are not used to the higher range of temperatures experienced in Moree. The full forecast can be accessed here: http://www.bom.gov.au/australia/heatwave/

In the coming week, mild heat wave conditions are predicted to occur in the Gulf region, the eastern half of Queensland and Big Rivers area (NT).

Heat wave forecast starting Sunday 15 November through to Tuesday 17 November 2020