Seasonal Climate Outlook Message for June to September 2003
The bottom line
SOI Continues To Fluctuate Dave McRae Qld Dept of Primary Industries (dated 2nd June 2003)
The latest climate data highlights that the 2002/03 El Nino sea temperature pattern has largely broken down. However it is important to point out that this does not automatically mean an immediate end of the current drought.
Rainfall probabilities for Queensland, although an improvement over the situation this time last year, are currently not high enough to produce widespread drought-breaking rains in the medium term. While the chance of a new El Nino developing remains fairly low (but not impossible) it should be remembered that much of Queensland remains drought declared and the overall situation may not dramatically improve until summer.
Of some concern are the fluctuations of the SOI during May. The 30day average of the SOI has fallen from a high of plus 3.6 on the 14th May to minus 8.1 as of the 2nd June. Some changes to improve the overall seasonal outlook for Queensland include a return to more positive SOI values (last 'Consistently Positive' SOI phase was in March 2001) as well as the complete cool down of sea surface temperatures especially for the region running along the equator east of the International Date Line.
The full story
Climate Watch Dave McRae Qld Dept of Primary Industries (Dated 2nd June 03)
The latest climate data highlights that the 2002/03 El Nino sea temperature pattern has largely broken down. However it is important to point out that this does not automatically mean an immediate end of the current drought.
Rainfall probabilities for Queensland, although an improvement over the situation this time last year, are currently not high enough to produce widespread drought-breaking rains in the medium term. While the chance of a new El Nino developing remains fairly low (but not impossible) it should be remembered that much of Queensland remains drought declared and the overall situation may not dramatically improve until summer.
Of some concern are the fluctuations of the SOI during May. The 30day average of the SOI has fallen from a high of plus 3.6 on the 14th May to minus 8.1 as of the 2nd June.
Based of the monthly value of the SOI from the end of April (minus 5.9) to the end of May (minus 5) the SOI is in a 'Consistently Near Zero' phase.
For those interested in following historical rainfall patterns more closely, some of the other years that have had a 'Consistently Near Zero' phase at the end of May include 1932, 1933, 1937, 1939, 1944, 1948, 1949, 1954, 1959, 1966, 1967, 1976, 1982, 1984, 1986 and 1996. It can be useful to find out what rainfall and farming conditions where like in your area for June to August in those years.
Based on the recent SOI pattern, most of the southern two thirds of Queensland have a 50-70% chance of getting above the long term June to August median rainfall. This compares with a 30-50% chance for most of the peninsular and gulf regions.
As always, when using any probability based forecast system, it is important to consider the alternate view. For example, currently Marburg in south east Queensland has a 71% chance of getting above the long term June to August median rainfall of 105mm. This also means that there is a 29% chance of not getting above 105mm.
Another way of looking at this is that in 7 years out of 10 (or around three quarters of years) with the current SOI pattern, Marburg has received more than 105mm for June to August. Therefore in 3 years out of 10 (or around one quarter of years) with this SOI pattern, Marburg has received less than the long term June to August median rainfall of 105mm.
It's also worth pointing out that at this time of year the long term median rainfall totals for north and west Queensland are quite low. For example Quilpie has a long term June to August median rainfall of 37mm, Windorah has 30mm, Winton and Mareeba have 23mm, Boulia has 17mm, Cloncurry has 14mm, Laura has 6mm and Normanton has 2mm.
The last passage of the MJO (40day wave) influenced Queenslands weather around the 14-18th May producing some rainfall events largely concentrated along the coastal strip with only limited falls occurring in other parts of the state.
The MJO is simply a band of low atmospheric pressure originating off the east coast of central Africa travelling eastward across the Indian Ocean and northern Australia roughly every 30 to 50 days. While it is a tropical phenomenon, it appears to indicate the timing of potential rainfall events (but unfortunately not rainfall amounts) over central and southern Queensland.
If its' timing remains current, it would next be expected around late June.
Rainfall probabilities across the rest of Australia vary. For the NSW/Queensland boarder strip the chance of getting above the long term median rainfall level remains at around 50-70%. Probabilities across the rest of NSW though are generally lower at 20-40%.
Victoria, Tasmania, South Australia and most of Western Australia also have a relatively low chance 20-40% of getting above the long term June to August median rainfall. Rainfall probabilities for most of the Northern Territory though are higher at around 50-70% (keeping in mind that median rainfall levels are generally low there at this time of year).
The latest release (dated May 19) from the Climate Prediction Centre (CPC) www.cpc.ncep.noaa.gov/ in the United States highlights that the El Nino event has largely broken down during March and April. Only a small area of warmer than normal water 'stubbornly' remains in the central equatorial Pacific west of the international dateline.
Sub-surface and sea surface temperature anomalies have decreased by more than 0.5-2°C throughout much of the eastern and central equatorial Pacific. The low-level westerly wind bursts that largely drive the El Niño system have also generally dissipated in the equatorial Pacific and been replaced by stronger than average easterly winds.
However, some concern remains over potential for the last MJO to trigger more of these westerly wind bursts.
While the chance of a new El Nino developing remains fairly low (but not impossible) it should be remembered that most of Queensland still has some way to go in terms of the end of the current drought.
Some changes to improve the overall seasonal outlook for Queensland include a return to more positive SOI values (last 'Consistently Positive' SOI phase was in March 2001) as well as the complete cool down of sea surface temperatures especially for the region running along the equator east of the International Date Line.
Ocean and coupled ocean/atmosphere forecast models (GCM's) give an indication as to likely ENSO development out to 9 months. Of 11 models that forecast out to October 2003, 9 indicate the development of a neutral sea temperature pattern, 1 indicates an ongoing El Nino (or warm) sea temperature pattern and 1 indicates the potential development of a La Nina (or cold) sea temperature pattern.
Of the 9 models that forecast out to January 2004, 7 indicate the development of a neutral sea temperature pattern while 2 indicate the development of a La Nina sea temperature pattern.
GCM outputs should be viewed cautiously at this time of year as we are in the so-called "predictability barrier" between March and June. More details can be found at www.bom.gov.au/climate/ahead/ENSO-summary.shtml
Due to the size of the area covered, the information provided in this column is of a fairly broad nature. For those readers who require more specific climate information, we recommend referring to Australian Rainman, the latest "Climate Note" at www.dpi.qld.gov.au/climate or contact us through the DPI Call Centre on 13 25 23.
