Seasonal Climate Outlook Message for June to September 2002

The bottom line

SOI Rapidly Falls Dated 05/06/02

The key point for the June to August seasonal outlook is the continuation of the relatively low rainfall probabilities that have existed across much of Queensland for most of this year.

Currently there is only a 20-50% probability of receiving median rainfall for June to August for most of the south, south-east, west and coastal regions of the state. Across central and north Queensland the probability of receiving or getting the long term median rainfall for June to August varies between 30-70% depending on location.

The monthly value of the SOI at the end of April was -3.4 and at the end of May was -13.8. Based on this shift in the monthly value of the SOI over April and May the SOI is now in a "Rapidly Falling" Phase. The 30day average of the SOI as of the 5th June was -19.3. A daily updated recorded message with the 30day average of the SOI is also available on 46881439.

The rainfall outlook for later this year (eg. August to October) will depend on just how the currently changing ENSO pattern continues to develop. If the SOI stays deeply negative from now on then we would expect comparatively low rainfall probability values to extend throughout eastern Australia.

Sea-surface temperature patterns in the Central Pacific will also play a key role in future rainfall and temperature patterns for Queensland. The central equatorial Pacific Ocean region, where the international dateline intersects with the equator is now +0.9 C above normal. This type of pattern by itself historically has resulted in reduced rainfall for many areas of Queensland.

The 30-50 day intra-seasonal oscillation (or 'MJO') has had little recent direct impact on reflected high latitude cloud bands that occasionally affect Queensland rainfall. While there was a slight rise in the value of the SOI with the last 30-50day oscillation (in early May), there wasn't any wide spread rainfall events coinciding with its passage. It is next expected around mid to late June (keeping in mind that the timing of this phenomenon can alter).

The full story

SOI Rapidly Falls Dated 05/06/02

Based on the recent pattern of the SOI over April and May, the probability of above median rainfall across much of Queensland for June to August continues to remain relatively low.

Currently there is only a 20-50% probability of receiving median rainfall for June to August for most of the south, south east, west and coastal regions of the state. Across central and north Queensland the probability of receiving or getting the long term median rainfall for June to August varies between 30-70% depending on location.

The monthly value of the SOI at the end of April was -3.4 and at the end of May was -13.8. Based on this shift in the monthly value of the SOI over April and May the SOI is now in a "Rapidly Falling" Phase. The 30day average of the SOI as of the 5/6 was -19.3. A daily updated recorded message with the 30day average of the SOI is also available on 46881439.

The outlook for later this year (eg. August to October) will depend on just how the currently changing ENSO pattern continues to develop. If the SOI stays deeply negative from now on then we would expect comparatively low rainfall probability values to extend throughout eastern Australia.

It is essential to remember that when dealing with probabilities to also consider the additional information that probabilities provide. For example, based on the recent pattern of the SOI there is only a 38% chance of getting the long term June to August median rainfall of 85 mm at Roma. Therefore there is a 62% chance of not getting the June to August median rainfall.

Another way of looking at this is that in approximately one third of years (approximately 3 to 4 years out of 10) with the current SOI pattern has Roma received its long term median June to August rainfall.

Therefore in around two thirds of years (6-7 years out of 10) with the current SOI pattern below median rainfall has been recorded at Roma for June to August.

For those who like to follow historical patterns more closely years in the past that had a "Rapidly Falling" SOI phase in April/May include 2001, 1999, 1972, 1958, 1957, 1953, 1947, 1935 and 1934. What was the rainfall and/or farming conditions like for June to August in your area for those years? Details of the rainfall in those years can be found at the 'Long Paddock' internet site www.longpaddock.qld.gov.au or in the Australian Rainman CD.

Sea-surface temperature patterns in the Central Pacific will be the key to future rainfall and temperature patterns for Queensland. The central equatorial Pacific Ocean region, where the international dateline intersects with the equator is now +0.9 C above normal. This type of pattern by itself generally results in reduced rainfall for many areas of Queensland.

The 30-50 day intra-seasonal oscillation (or 'MJO') has had little recent direct impact on reflected high latitude cloud bands that occasionally affect Queensland rainfall. While there was a slight rise in the value of the SOI with the last 30-50day oscillation (in early May), there wasn't any wide spread rainfall events coinciding with its passage. It is next expected around mid to late June (keeping in mind that the timing of this phenomenon can alter).

If anyone requires more climate related information contact the DPI Call Centre on 13 25 23. Alternatively try the DPI's climate web site www.dpi.qld.gov.au/climate on which the "Climate Note" can be found.