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 MJO this summer

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Much of our moisture originates from the tropics this time of year. The chart below shows the MJO currently in Phase 3 out in the Indian Ocean. A weak pulse may affect Australia (Phases 5-6) at the end of January. rather than the MJO, the latest NCEP report states “stationary La Niña signal continuing to dominate the overall global tropical convective field”

The Madden – Julian Oscillation (MJO) is a tropical disturbance that moves eastward around the global tropics every 30-60 days and has proven to influence rainfall and temperature conditions. The strength of the MJO may increase or decrease as it progresses eastwards, affecting the level of convection and influence on both precipitation and temperature. The diagram below is used by scientists to track the path of the MJO showing predicted dates through various phases (see last weeks edition for MJO explainer). This illustrates the MJO currently inactive inside the circle, then increasing in strength through week 2 in January as it reaches the maritime continent. Not all models are aligned and some show no signal for the MJO whatsoever. A short YouTube cartoon explaining the MJO can be found here

 
 

Monitoring the SAM

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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. 

Monitoring the MJO this summer

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Much of our moisture originates from the tropics this time of year. The chart below shows a pulse of moist air in Phase 5 over Australian longitudes (green line) around 10-14 January. Tracking this tropical moisture can help us understand when rain-bearing systems or heatwaves are more likely.

The Madden – Julian Oscillation (MJO) is a tropical disturbance that moves eastward around the global tropics every 30-60 days and has proven to influence rainfall and temperature conditions. The strength of the MJO may increase or decrease as it progresses eastwards, affecting the level of convection and influence on both precipitation and temperature. The diagram below is used by scientists to track the path of the MJO showing predicted dates through various phases (see last weeks edition for MJO explainer). This illustrates the MJO currently inactive inside the circle, then increasing in strength through week 2 in January as it reaches the maritime continent. Not all models are aligned and some show no signal for the MJO whatsoever. A short YouTube cartoon explaining the MJO can be found here

 
 

Multi-week model analysis (8-28 days)

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The broad-scale pattern has finally aligned to some degree, with cooler moist air favoured to camp in the Australian region for possibly the next three to four weeks. The guidance suggests impacts and moisture receding into January, although this will largely be determined by the next move of the MJO - which is currently not acting to script. One concern for regional Qld areas is the 7-day SST anomaly showing a cooling of waters in the Coral Sea again, reducing moisture availability - at odds with the La Niña signal.

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Model commentary: scrolling through the various weekly forecast intervals, the peak opportunity for rainfall appears to be through until around the 28 December. The JMA model is bullish wet for a month, albeit tapering off in January. The IRI model seems to be picking up on the cooling Coral Sea and is less enthusiastic about January. ACCESS-S continues unabated for a wet finish to December, so nothing has changed with it. The 16-day NCEP has small sporadic falls showing in the majority of areas, much more cautious even than the 9-day ECMWF loop. Keep an eye on the Meteologix 10 day Forecast XL for a full summary of all ‘weather models’ as events draw closer for your area: https://meteologix.com/au

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. 

Monitoring the MJO and tropical moisture this summer

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Much of our moisture originates from the tropics this time of year. The LHS chart shows tropical moisture (rising air at high altitude) over Australian longitudes (green shading). Similarly, RHS charts for the last 2 weeks, with low air pressure off eastern and northern Australia. Tracking this tropical moisture can help understand when rain-bearing systems are more likely.

The CPC (US) reports the Madden-Julian Oscillation (MJO) being “better organised” in Phase 5 this week (Australian region). The dynamical model spread for the next move of the MJO remains high, as ensemble means favour a decline of the intraseasonal signal over the Maritime Continent and western Pacific likely due to destructive interference with the ongoing La Niña. This limits forecast confidence on the predicted evolution and strength of the MJO into late December.

For a basic MJO explainer and why we need to watch the MJO, see the following animation here: https://www.youtube.com/watch?v=SwoB-2nSnJ0

 
 

9-day ECMWF rainfall outlook

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Fresh today, the European ECMWF 9-day model is bullish on rainfall for large tracts of eastern and northern Australia. A weak MJO is camped to the north of Australia and the waters in the north-west are very warm. The synoptic pattern shows low air pressure deepening over western and central Australia, consistent with the rainfall outlook.

The tropics have finally come to life on a decent scale. While this ECMWF model is bullish, it is prudent to survey other global models for refining weather-dependent decisions over the coming week.

Visit meteologix.com/au and navigate your way the Model XL forecast for your location.

Access courtesy https://meteologix.com/au

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