THE CLIMATE KELPIE BLOG: December 2017 mega storm, observed outcomes

Posted by BCG on 14th March 2018

In a four day period during the 2017 harvest (30 November to 3 December), growers were warned of possible extreme damaging rainfall and weather conditions.

This weather system resulted in Echuca breaking a 159-year-old daily rainfall record with 123mm recorded in 24 hours.

The Bureau of Meteorology’s Luke Shelley explained that it was extremely complex to forecast the details of the system. Prior to the event, international and Australian weather prediction modelling indicated that the southeast of Australia faced a certain severe weather event.

“Although western Victoria largely missed out, heavy rainfall was realised throughout the outer-eastern parts of the greater Melbourne area and throughout northeast Victoria,” Dr Shelley explained.

Other parts of southeast Australia received severe weather: Tasmania experienced 30-40cm of December snow in the Central Highlands and higher peaks, and South Australia and New South Wales were also affected, with Kalangadoo in South Australia experiencing extensive wind damage and 2-3cm hail.

“Due to the meteorologically complex and unusual nature of the forecast event, there was some degree of uncertainty in the precise event outcomes.” Dr Shelley elaborated.

The figure below shows that the forecast predicted more rainfall in western Victoria than eventuated, but forecasters were correct in warning that dangerous weather was to be experienced in parts of Victoria.

“The Bureau and Victorian State Government Agencies’ pre-event messaging reflected their concerns over the potential for severe impacts in some areas, based on the forecast information.”

Dr Shelley reiterated how dangerous the conditions were.

“During the event, Victoria’s SES recorded over 2500 requests for assistance, with about 900 more requests spread over NSW, South Australia and Tasmania.”

“Considerable community preparation was done in response to the warnings. This is always disruptive but pays dividends where forecast conditions eventuate.”

“Where heavy rain did not fall, some members of the public were reasonably concerned that a great deal of effort had been put in for an apparent non-event. We understand that, but we still need to call it as we see it. We’re taking feedback on board, particularly in terms of how we best communicate the forecast uncertainties for these events.”

Dr Shelley attended the recent BCG Trials Review Day, and travelled to meet farmers in the Southern Mallee to get a better understanding of what growers are looking for when it comes to weather and climate information.

BCG and the Bureau of Meteorology are working together on projects including Rural Research and Development for Profit ‘Improved use of seasonal forecasting to increase farmer profitability’ and ‘Forewarned is Forearmed: managing the impacts of extreme climate events’.

For more information about these projects visit the website, www.bcg.org.au, or contact the office on 03 5492 2787.