Drought scenario not over: El Nino-SST pattern persists by Dave McRae, DPI/AFFS Centre for Climate Applications

The map shows the variation in the sea surface temperatures from November 2001 to August 2002. Areas coloured yellow and red have warmed, while areas coloured blue have cooled over this period. As can be seen, there has been significant warming in the central Pacific west of the international dateline and along the equator.

ACCORDING TO recent sea temperature reports sourced from the Climate Prediction Centre (www.cpc.ncep.noaa.gov) in the Unites States and the Bureau of Meteorology (www.bom.gov.au). an El Nino sea surface temperature (SST) pattern currently exists in the Pacific Ocean.

These reports highlight not only the tell-tale signs of an El Nino, such as warmer than normal surface and subsurface sea temperatures throughout the central Pacific Ocean, but also a partial breakdown of the pattern of cooler-than-normal water that has existed off the South American coastline over the last few months.

As well, strong westerly wind bursts (rather than the 'normal' south-east trade winds) have been recorded along the equator near the international dateline. Based on previous El Nino events as well as current ocean and atmospheric conditions, this SST pattern is predicted to persist through to autumn 2003.

Warmer than normal pattern up to January, mixed forecast up to April

Given the existence of this pattern, the output of the reputable long-range ocean and coupled ocean/atmosphere forecast models (GCMs) is of interest. Of the 12 surveyed models, nine forecast a warmer-than-normal SST (EI Nino) pattern through to January 2003.

Of these 12 models, 10 currently provide a forecast through to April 2003. Four of these predict warmer-than-normal sea surface temperatures through to April. While the other six models predict a return to neutral sea surface temperatures, it is worth noting that none forecasts the possible development of a La Nina next year.

Our strong advice, therefore, remains to monitor Southern Oscillation Index trends and SST patterns on a monthly basis.

Each EI Nino event is different in regard to rainfall patterns and drought areas. The Bureau of Meteorology has an interesting site (www.bom.gov.au/climate/) which provides a good summary of the impact of previous El Ninos.

Previous EI Ninos include 1902-03, 1905-06, 1911-12, 1913-14,1914-15,1919-20, 1925-26,1940-41,1941-42, 1946-47, 1951-52, 1957-58, 1964-65, 1965-66, 1969-70, 1972-73, 1977-78, 1982-83, 1987-88, 1991-92, 1993-94, 1994-95 and 1997-98. What were the seasonal conditions in your area for those years?

For those interested, the latest seasonal outlook maps and forecasts are available at www.dpi.qld.gov.au/climate. The Long Paddock web site (www.longpaddock.qld.gov.au/) is also another good source of climate information.