Bureau Of Meteorology:
ENSO Wrap-Up: La Niña continues to develop in the Pacific
CURRENT STATUS as at Wednesday 4 August 2010
ll indicators in the Pacific Ocean show that we are now in the early stages of a La Niña event. Computer models predict the central Pacific will continue to cool in coming months, indicating some further strengthening of the event is likely.
Signs of an emerging La Niña event have been apparent in the equatorial Pacific for several months. Pacific Ocean temperatures have cooled steadily throughout the year, the Southern Oscillation Index (SOI) has increased in value and is currently around +21, trade winds continue to be stronger than average and cloudiness has remained suppressed over the central Pacific. All of these key indicators have now reached or exceed La Niña levels.
Source: BOM (Chart Updated Tuesday 3rd August 2010)
WA Dept of Agriculture: Growing Season Outlook
August 2010
Contributors: David Bowran, Fiona Evans, Ian Foster, Phil Goulding, David Stephens
Summary:
Moderate Strength La Nina conditions have developed in the eastern and central Pacific. An enhanced sea surface temperature gradient northwest of Australia, and below normal pressure near Darwin, are providing a favourable set-up for the spring finish in eastern Australia. In contrast, a dry pattern over southern WA has been related to higher than normal pressure and a reduced temperature gradient west of Perth. These have combined to weaken cold frontal activity and moisture inflow into the WA wheat-belt.
A consensus of most climate models is that rainfall is likely to be below normal for the next 3 months over most parts of the WA grainbelt. For eastern Australia, better rainfall and crop prospects are indicated and a La Nina pattern adds confidence to the rainfall outlook. For northern and eastern areas of the WA wheatbelt low soil moisture reserves and low yield potentials requires a conservative approach to crop management for the remainder of the season.
Click here for complete Growing Season Outlook.
Elders Weather Medium Term Outlook (Issue Notes)
Issued 30 Aug 2010
The hemispheric long wave pattern has been relatively slow moving in recent weeks. There are three main troughs. Currently the most significant troughs are near the longitudes of the southwest Indian Ocean, Western Australia, and the southeast Pacific.
Summary: Over southern and eastern Australia the cold front events with potential to bring widespread rain are now expected about 5 September to 9 September, 22 September to 26 September, and 26 September to 30 September. Rain events originating in the tropics and moving south are possible about 15 September to 19 September, and 19 September to 23 September. Over Western Australia the strongest cold fronts should occur about 20 September to 24 September, 25 September to 29 September, and 2 October to 6 October.
For more information click here.
Elders Weather 12 Month Rainfall Forecast
Issued 06 Aug 2010
During July, waters over the eastern Pacific continued cooling and trade winds over the western Pacific remained anomalously strong. The ENSO system is now in a La Nina state, as previously expected. The current La Nina event is likely to peak sometime between October 2010 and February 2011.
Forecasts through the austral spring continue to show likely rainfall close to or above median for southern QLD, NSW and Victoria. The outlook stays generally near median for southwest WA and TAS during this period.
Early rainfall forecasts for summer 2010/2011 are generally near or above median for summer-rainfall regions of northern and eastern Australia, driven by the high probability of a La-Nina event. At present the impact of La Nina on VIC, SA and WA is (as usual) expected to be minimal.
For more information click here.
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