Seasonal Climate Outlook Message for August to November 2001

The bottom line

SOI message 15th August 2001.

The 30-day average of the Southern Oscillation Index (SOI) is -3.0 as of the 15th August.

Based on a Consistently Near Zero SOI phase in June/July, there is a wide range of rainfall probabilities across Queensland for the August/October period, with the main areas of low rainfall probabilities being in NE Qld.

The Livingstone, Fitzroy, Duaringa and Emerald shires north to Cape York with parts of the Diamantina, Barcoo, Longreach, Perry, Monto and Eidsvold shires all have only a low 20-40% probability of getting or exceeding the long term median August to October rainfall.

For the rest of Queensland there is a 40-60% chance of getting above the long term median August to October rainfall.

Also an important point to remember is that August and September across most of Queensland are normally the two driest months of the year in terms of absolute rainfall.

The key point for readers who follow the movements of the Southern Oscillation is to keep track of any shifts in the monthly value of the SOI over the next couple of months. Any substantial fall at this time of year would reduce rainfall probabilities for many areas of the state for the coming summer.

The full story

Review of Climate Forecasts and Information 1st August 2001. Next update 5th September. Seasonal rainfall outlook

For most of eastern Australia there is a reduced chance of getting the median August-October rainfall this year.

The majority of districts in Queensland have only a 40-50% chance of getting median August-October rainfall. However, the probabilities decrease to only 20-30% in the north-east near Charters Towers and Cooktown. Also, the Central Highlands and most coastal districts between Rockhampton and Cape York have only a 30-40% chance of at least median August-October rainfall.

In the drought-stricken regions of the southern Queensland, rainfall probabilities have not improved significantly.

More detailed probabilities can be found in Australian Rainman.

Other States The north-east corner of NSW has the highest probabilities of above-median August-October rainfall with probabilities between 60-70%. However most of the rest of the state, and also Victoria, Tasmania, and Western Australia have equal chances of above or below median falls. In South Australia, the Eyre Peninsula has similarly equal probabilities; however in the northern half of the state, the probabilities are slightly lower (30-40%).

Remember, a 50% chance of above-median rainfall means there are equal chances of it being a wetter or drier 3 months based on the phase of the SOI.

The 30-50 day oscillation

The 30-50 day oscillation is next due to have an influence on Queensland's rainfall towards the end of August. Although strictly speaking it is a tropical phenomenon, it appears to influence the timing of rainfall events rather than the actual amount of rain. This forecast system is based on experimental research only.

Future ocean temperature development

Ocean temperatures in the equatorial Pacific Ocean are in general presently close to the long-term average. However, overall the ocean has warmed significantly over the past 4 months and this can be seen at one of the Bureau of Meteorology's web sites: http://www.bom.gov.au/bmrc/ocean/results/ocean_anals/SEQ_Equator/2001/Jun.gi f

Most of the General Circulation Models that forecast El Nino and La Nina are predicting that we will be in a "neutral" event in 6 months time, although slight warming will take place.

A summary of these model outputs can be found at: http://www.bom.gov.au/climate/ahead/ENSO-summary.shtml Another good website providing an update of conditions in the equatorial Pacific Ocean is: http://www.pmel.noaa.gov/toga-tao/el-nino/forecasts.html#enso

Although we have the necessary preconditions for an El Niño, it remains to be seen whether the oceans will warm sufficiently.

Last updated: 14 August 2001