Spring is a notoriously windy season but whether southern Australia is calmer or windier than usual comes down to the Southern Annular Mode.
So, what is the Southern Annular Mode?
The SAM is simply an index that’s used to monitor the position of a belt of westerly winds that flow from west to east between Australia and Antarctica.
When the SAM is in a negative phase, these westerly winds, and the cold fronts and low pressure systems they carry, are located further north than usual for that time of year.
When the SAM is positive, the westerly winds, cold fronts and low pressure systems are located further south than usual.
The SAM can have a notable impact on Australia’s weather. Negative phases of the SAM during spring can:
- Reduce rainfall over southeast and eastern Australia.
- Promote strong westerly winds over southern Australia, increasing wind power generation.
By contrast, positive phases of the SAM in summer can:
- Reduce wind power generation in southern Australia.
- Increase rain over eastern and southeast Australia.
- Reduce the chance of extreme heat.
A recent example of negative SAM’s influence on Australia’s weather was the 2019/20 Black Summer. During that season, strong westerly winds from the interior promoted dry, hot and windy weather across eastern Australia. These conditions led to record-breaking heat and a very dangerous fire season, with millions of hectares burnt across NSW, QLD and VIC.
By contrast, this years’s run of predominantly positive SAM has helped cause record-breaking rain and below-average temperatures and bushfire activity in eastern Australia. This was on show during February and March 2022, when high pressure lingered over the Tasman Sea, providing a years worth of rain in just a few days over the east coast of Australia.
During La Niña years, the SAM usually remains in a predominantly positive phase. During El Niño, the SAM is more commonly in a negative phase, however this link is not as strong as during a La Niña.
Does spring 2022 look windy?
Looking ahead, the SAM is likely to remain mostly positive for much of spring with a looming La Niña on the horizon.
As a result, strong wind events are likely to be less frequent in southern Australia this spring, with more periods of settled conditions.
The image below shows the SAM is forecast to be positive for much of the next month, which is a trend that could continue for much of spring.
Image: SAM forecast, showing positive SAM is forecast for much of the next month (green line). Source: Bureau of Meteorology
However, it doesn’t mean wind will drop off everywhere. A steady stream of easterly winds can still flow across NSW, VIC, TAS during positive SAM phases as we move into the warmer months.
In southern Australia, while the number of strong wind events should be reduced over the season, fierce winds will still push through at times. The SAM has no effect on the strength or severity of strong wind events when they do occur.
How DTN APAC forecasts wind energy and its power.
DTN APAC, a DTN company, offers wind and power generation forecasting to assist in determining your wind farm’s output, reducing costly errors.
Whether you have an existing windfarm, or looking for an optimal wind farm location, we provide crucial data to give you greater awareness of your generation capacity. From vertical wind profiling, to identifying alternative scenarios and RAMP events, we have you covered. We can assist with:
- Rapid Update Forecasting– 5-minute forecasting up to 72 hours and hourly forecasting out to 10 days for full awareness.
- RAMP Event Prediction- Understand when significant generation impacts will occur so you can mitigate risk.
- Advanced Generation Forecasting-Multi-level wind profiles, meta-data management and input data QC ensures precision.
We work closely with you, pushing the boundaries of science and technology, to identify and fulfil your individual business needs. A tailored and consolidated solution, making your everyday more effective. For more information, please contact us at apac.sales@dtn.com.
