Seasonal Climate Outlook Message for May to August 2002

The bottom line

Continuation of relatively low rainfall probabilities (Dated 15/05/02)

The key point at present is the continuation of relatively low rainfall probabilities over most of Qld for May to July.

Given the potential development of an El Nino later in the year the latest diagnostic discussion (dated May 9) by the USA Climate Prediction Centre is interesting. They state that warmer than normal sea surface and subsurface temperatures were observed throughout most of the far eastern equatorial Pacific Ocean. While this strong warming trend over February to April resulted in heavy rainfall along the coasts of Ecuador and northern Peru, there was only limited warming of sea surface temperatures in the key regions of the central Pacific Ocean during this period.

Therefore it appears a trigger event such as strong westerly wind bursts in the central Pacific or a Kelvin Wave is still required for an El Nino event to occur. It will be interesting to see if the recent passage of the 30-50day intra-seasonal oscillation in early May helped create the needed strong westerly wind bursts and/or Kelvin Wave.

We therefore continue to strongly recommend closely monitoring information on SOI trends and sea surface temperature patterns over the next few months. A sustained fall in SOI values between March and May would further substantiate the potential for reduced rainfall in many districts for the following 6-9 months.

The 30day average of the SOI has fallen over the last week and as of the 15th of May is -7.1.