September has been a lean month for rainfall across eastern Australian cotton areas, however, the SAM is predicted to work its way positive, along with ENSO - shifting towards La Nina (SOI now +10). The Indian Ocean remains borderline wet phase and will go down as a weak event that never met expectations. With the weaker negative IOD and approaching La Nina, one would expect cooler temperatures and lower crop ETo through the remainder of the calendar year.  For more information on what the climatic indicators mean, click here. 

Central and northern NSW catchments were the main beneficiaries through winter with dry-season rain falling in some parts of northern Australia while the balance remained average.

Mean temperature deciles showing warmer than average with the exception of a few pockets in NSW.

 

A similar outlook from a month ago with all models showing a wetter trend across eastern Australia off the back of a developing La Nina and warm ocean temperatures around Australia's perimeter. Temperatures set to be cooler or average for the remainder of the year also.

The story of this month is the growing consensus among global models predicting a La Nina to finish 2021. A wetter (negative) Indian Ocean Dipole peaking next month just inside wet thresholds and beginning to retreat in November. Click on the image to go the full BOM model time-series analysis.
 

Research findings by Hendon et al, (2014) at the Centre for Australian Weather and Climate Research show the Southern Annular Mode to be the leading mode of circulation variability through parts of inland eastern Australia; particularly during 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 the CPC (US) shows observations of the SAM (or Antarctic Oscillation Index) above the black zero line in the positive phase for the remainder of September.
 
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.
 

 

Drought is a major risk to Australia with extended periods of drought affecting our social, economic and environmental systems. The newly released report by the Intergovernmental Panel on Climate Change contains significant new assessments of the science and future projections of drought. A special briefing by the ARC Centre for Climate Extremes (CLEX) makes the following observations.
 

KEY POINTS

• Droughts are increasing over parts of southeast and southwest areas of Australia and are projected to continue to increase in the future.

• Some types of drought have decreased in northern Australia associated with increased wet season rainfall.

• No definitive links have been made between most recent Australian droughts and climate change due to high natural variability in rainfall.

• Climate model projections are consistent in suggesting an increase in many types of drought, in particular over southern Australia.

• Some attributes of drought (e.g. intensity) are not well simulated in global climate models, pointing to areas requiring further scientific development.

Authors: Anjana Devanand, Andy Pitman, Nerilie Abram, Ailie Gallant, Andrew King, Anna Ukkola and Jason Evans

To access the 3-page summary, click on the image below.