Climate Outlook and Review August 2018 Author: Prof Roger C Stone
Overview The European, UK, and US long-term climate models that focus on forecasting central Pacific sea surface temperatures are continuing to predict further development of an El Niño. Most El Niño events persist until the southern hemisphere autumn (eg April/May). Consequently, most rainfall forecasts for northern Australia, especially north east Australia, currently indicate only low probability values of exceeding the respective long-term median rainfall right through to and including summer 2018/19. However, the statistically based SOI phase system now indicates some relief rainfall during August-October for some regions. It needs to be emphasised that median rain at this time of year, in terms of absolute values, is low anyway suggesting no real clear end in sight to the current drought conditions. For Queensland (and northern Australia generally), using our statistical system (SOI phases) and based on a rapidly rising SOI Phase at the end of July, for the August to October 2018 period, the SOI phase system shows generally around a 50%-70% probability of exceeding seasonal long-term median rainfall for many Queensland regions (see map). However, some areas are now beginning to suggest above median rainfall (see maps attached). Note: these percentages are relative for this time of the year. The improved BoM POAMA 2.4 model continues to indicate low rainfall probability values for most regions for the August to October total period but with lower rainfall probability values for New South Wales and South Australia (Figure 6). An exception is for parts of SE and central Queensland where probability values are a little higher. For the longer term (e.g. spring/summer October to December) the European ECMWF GCM forecast system suggests below the longterm normal rainfall (Figure 8). The MJO: The MJO would most likely be due again in about fourth week in August. Temperatures: for regions, the BoM POAMA 2.4 system indicates above median maximum temperature probability values for much of Northern Australia. The SOI phase system is suggesting close to normal maximum temperature values for the August to October period, 2018.
Figure 1: Forecast rainfall probability values for Queensland - probability of exceeding the respective long-term seasonal median values overall for the total August to October 2018 period. Regions shades blue have 60%-70% probability of above median rainfall values. Regions shaded darker grey have a 50%-60% probability of exceeding median rainfall values relative to this period of exceeding median values.
Figure 2: Probability of maximum temperatures averaged over the three-month period August to October 2018 being above the long-term median for this time of the year. Regions shaded dark grey have about 50%-60% chance of above median maximum temperatures Regions shaded lighter grey have a 40% - 50% probability of exceeding median temperature values.
Figure 3: Probability of minimum temperatures averaged over the three-month period August to October 2018 being above the long-term median for this time of the year. Regions shades blue have 60%-70% probability of above median minimum temperature values. Regions shaded grey have a 40% - 50% probability of exceeding median minimum temperature values.
Figure 4: Northern Australia probability rainfall values, averaged over the threemonth period August to October 2018 of being above the long-term median for this time of the year. Regions shades blue have 60%-70% probability of above median rainfall values. Regions shaded grey have a 40%-50% probability of above median rainfall. Figure 5: Forecast rainfall probability values for Australia for the overall period August to October 2018 (after Stone, Hammer and Marcussen, 1996). Regions shaded blue have a 60%-70% probability of above median rainfall. Regions shaded darker grey have a 50%-60% probability of above median rainfall for this particular overall period.
Figure 6: Bureau of Meteorology Forecast rainfall probability values for Australia for the overall period August to October 2018.
Figure 7 (a): Monthly SOI values since January 2010 the most recent phase is rapidly rising phase with the SOI very much on an oscillating roller coaster ride. The most recent 30-day average value to 31 July was plus 1.2 (+1.2). Figure 7 (b): recent trend in SOI values (30-day averages) as at 01/08/2018
Longer-term forecasts: The ECMWF and POAMA models provide useful assessments of longer-term rainfall probability values for agricultural regions. The ECMWF example below suggests about a 20-30% probability of above median rainfall for October to December 2018 for Queensland and Northern Territory. Figure 8: ECMWF forecast rainfall probability values for Australia and the region generally for October to December 2018 (Courtesy ECMWF). The forecast for most regions is about a 20-30% probability of above median rainfall for this seasonal period
Figure 9: CPC General Circulation Model forecast of sea surface temperature anomalies through to April 2019 this model is strongly suggesting further El Niño development over the coming months.
Recent forecast maps As these forecasts are issued for a three-month validity on a rolling monthly basis, it has been decided to provide a continuous reference to these forecasts, as below: Seasonal climate forecast valid 1 August to 31 October 2018 Seasonal climate forecast valid 1 July to 30 September 2018 Seasonal climate forecast valid June to August 2018 Seasonal climate forecast valid 1 May to 31 July 2018
Seasonal climate forecast valid 1 April to 30 June 2018 Seasonal climate forecast valid 1 March to 31 May 2018
Madden Julian Oscillation (MJO) According to BoM s, USQ s and NOAA s forecasting systems and analyses, the MJO may next be due again around fourth week in August. Please also refer to the interesting BoM website (below) for updated information on the MJO. The information below also presents a one-stop shop as requested from industry for such information to be available. For updated climate information Click on the following links: For the MJO For weekly SSTs For easterly (and westerly) wind anomalies across the Pacific For sub-surface temperatures across the Pacific For ECMWF forecast products (note the web site for this output has changed) For plume forecasts of SSTs in the central Pacific For a complete history of the SOI The Long Paddock Additional information on ENSO
USQ Research Centre for Applied Climate Sciences Please email Prof Roger Stone at Roger.stone@usq.edu.au This project is jointly supported by the Department of Agriculture and Fisheries, the University of Southern Queensland and Meat and Livestock Australia, MLA Donor Company