Seasonal Climate Outlook Message for February to May 2004

The bottom line

SOI Continues to Rise (18 February)

The 30day average of the SOI has continued its roller coaster ride and as of Wednesday 18th February is plus 4.8 (up from minus 12.8 at the start of the month).

Across much of the Warrego, western Darling Downs and Burnett there remains a reasonable 50-70% chance of getting above median rainfall for February to April.

However, across much of the far south west, central west and central north of the state the chance of getting above median rainfall is as low as 20-40%. For the rest of Queensland there remains no strong signal towards either wetter or drier than normal conditions for February to April with a 50/50 chance of receiving above median rainfall.

According to the Bureau of Met National Climate Centre (NCC) February update www.bom.gov.au/climate the Pacific Ocean has remained in a neutral sea surface temperature (SST) pattern.

While SST are slightly warmer than normal and there was some weakening of the south east trade winds, the Bureau do not believe there is a strong likelihood of an El Nino developing in the short term. The Bureau also state that the recent Kelvin Wave of sub surface warming should have only a minor impact on SST in the eastern Pacific when the wave reaches the South American coast in the next two to four weeks.

This differs from the comments made by the United States Climate Prediction Centre (CPC) www.cpc.ncep.noaa.gov/ in their February update where they placed a lot more emphasis on the December MJO passage and the effect it had on producing a Kelvin Wave.

During autumn and winter Kelvin Waves can be considered to be somewhat of a pre-cursor or early indicator that the risk of an El Nino developing is increasing. So it will be interesting to see what impact, if any, this Kelvin Wave will have and if any other Kelvin Waves or strong westerly wind bursts develop over the coming months. Key times to watch for this in terms of El Nino development will be during March to June.

Ocean and coupled ocean/atmosphere forecast models can be used to show likely SST development out to 9 months. Of 11 models that forecast out to June, 6 indicate the continuation of a neutral SST pattern while 5 suggest the potential development of an El Nino (or warm) SST pattern.

While it is positive that around half of these models highlight a continuing neutral SST pattern (rather than an El Nino), given current conditions our policy remains to recommend caution when considering the longer term outlook. It's also worth remembering that over autumn and early winter most models fall away in their forecasting skill.

So unless there is a very strong event coming as in 1997 (but which had limited effect here on rainfall) then some models do not tend to show an El Nino event until mid winter, by which time it is too late for us.

It may therefore be useful for businesses that are adversely affected by El Nino events to consider now what risk management strategies they could use if the likelihood of an event increases