EI Nino on horizon? monitor closely by Dave McRae Centre for Climate Applications, Queensland Department oj Primary Industries

Probability of exceeding Median Rainfall

THE CLIMATE Prediction Centre (CPC) in the United States has a very useful Internet site www,cpc.ncep.noaa.gov for monitoring conditions in the Pacific, In the early March ENSO (EI Nino/Southern Oscillation) diagnostics discussion release, the CPC states that the recent changes in ocean temperature patterns support the forecasts of the continued development towards an EI Nino event.

Warmer than normal subsurface temperatures were recorded throughout the equatorial Pacific during February 2002, By late in February equatorial SST anomalies exceeded + 1°C from 165°E to 1800W and in the far eastern equatorial Pacific near South America,

The warming of the ocean along the South American coast was due to the arrival of the Kelvin wave that has been propagating eastward from the central equatorial Pacific since mid-December, These conditions are often associated with the early stages of El Nino.

Other indicators have corroborated the current forecast. According to the CPC, Peruvian officials indicate the ocean warming has had significant impacts on fishing in the region. Their cold water anchovies have started to be replaced by tropical species, Similar changes in fish catches have been recorded in the early stages of previous EI Nino events.

It will be interesting to see to what extent this warming continues and what ramifications this will have, especially on eastern Australia's expected rainfalL However, more definitive information will not be available until later in autumn, due to the variability in equatorial patterns, especially sea surface temperature patterns over the next few months.

Watch for drop in SOI

As we remain concerned about the likelihood of an EI Nino developing, we will monitor the situation and provide updated information regularly. Our strong advice is to closely monitor information on SOl trends and sea surface temperature patterns. A dramatic drop in SOl values between March and May would, for example, further substantiate the potential for reduced rainfall in many districts, It is also worth remembering that across a large part of Australia, an El Nino event is not needed to reduce rainfall. Warmer than normal sea surface temperature patterns in the central Pacific (and coexisting negative SOl pattern) can form and negatively influence our rainfall patterns without there being an EI Nino.

For more climate-related information contact the DPI Call Centre on 13 25 23. Alternatively try the DPI climate web site www.dpi.qld.gov.au/climate and look for 'Climate Note' , This contains more detailed information including rainfall probability maps, SST information etc. A recorded message with the 30-day average of the SOl is also available on 07 4688 1439.

Current picture

In the meantime, despite the rise in the Southern Oscillation Index (SOl) over January and February, the probability of above-median rainfall from March to May remains low across much of the major graingrowing regions of eastern Australia.

Relatively low probabilities of only 30-50 per cent of getting above the long-term March-May median rainfall were forecast for the grain growing areas of southern and south-eastern Queensland, The probability of above-median rainfall also remained low (30-50 per cent) across much of northern, central and western NSW, northern SA, and most of central and southern WA.

Probabilities of above-median rainfall were higher - at around 60- 80 per cent - across northern Queensland, parts of the Northern Territory, northern WA and the south-eastern corner of SA, For most of the rest of these states, at the time Ground Cover went to press, based on the SOI there were no strong signals either way of the likelihood of the next three months being excessively wet or dry.

For those who like to follow historical patterns more closely, years in the past that had a 'Rapidly Rising' SOl phase in January- February include 2000, 1997, 1985,1984,1978,1977,1975, 1971, 1968, 1965, 1961, 1955, 1950, 1949, 1946 and 1944, What was the early autumn rainfall in your area for those years?

Region North