Is the drought over?
Last Update: Thursday, June 28, 2007. 4:54pm AEST
Has all this rain ended the drought?
Despite the last three or four weeks bringing some of the best rain for years to some parts of south eastern Australia, it's too early to say the drought is over.
There's a feeling though that after 10 years of below average rainfall, it might just be the case.
Vote in the poll - Is the drought over?
The National Climate Centre will at this stage only concede that there has been a 'significant change in the climate systems', and suggests that we're probably in for above average rainfall.
The areas around Newcastle, Gosford, Goulburn, Gippsland and even Sydney don't need to be reminded of those prospects - you could argue that those areas have alrready received their allocation. And while that rain has ben music to the ears of farmers and townies alike, flooding has been a major problem, a cruel irony after so many years of drought.
Acting Superintendant from the National Climate Centre, Neil Plummer, confirms there has been a change in the weather. He says last year south-eastern Australia was experiencing an El Nino event, similar to the dry spell we had in 2002 and for a number of years since then.
But earlier this year, the El Nino system broke down,and since then there has been a rapid transition to a La Nina phase, which is normally associated with wetter conditions.
"We can't say were are actually out of drought yet, but there are indications that the atmospheric and oceans conditions have changed to indicate us moving toward a La Nina system. It woud take an enormous force to turn that around, and there's a zero chance of us returning to a El Nino this year"
The evidence is not only in ocean temperatures, but also in the fact that over northern Australia there has also been excellent rainfall and very low temperatures. [Darwin recorded some of its lowest temperatures ever during June, sending Territories to the wardrobe looking for anything warm! More...]
Definitions [from the Bureau of Meterology]
La Niña translates from Spanish as "the girl-child". The term "La Niña" has recently become the conventional meteorological label for the opposite of the better known El Niño.
The term La Niña refers to the extensive cooling of the central and eastern Pacific Ocean. In Australia (particularly eastern Australia), La Niña events are associated with increased probability of wetter conditions.
Changes to the atmosphere and ocean circulation during La Niña events include:
- Cooler than normal ocean temperatures across the central and eastern tropical Pacific Ocean.
- Increased convection or cloudiness over tropical Australia, Papua New-Guinea, and Indonesia.
- Stronger than normal (easterly) trade winds across the Pacific Ocean (but not necessarily in the Australian region).
- High (positive) values of the SOI (Southern Oscillation Index).
El Niño translates from Spanish as 'the boy-child'. Peruvian fisherman originally used the term - a reference to the Christ child - to describe the appearance, around Christmas, of a warm ocean current off the South American coast.
Nowadays, the term El Niño refers to the extensive warming of the central and eastern Pacific that leads to a major shift in weather patterns across the Pacific. In Australia (particularly eastern Australia), El Niño events are associated with an increased probability of drier conditions.
Changes to the atmosphere and ocean circulation during El Niño events include:
- Warmer than normal ocean temperatures across the central and eastern tropical Pacific Ocean.
- Increased convection or cloudiness in the central tropical Pacific Ocean - the focus of convection migrates from the Australian/Indonesian region eastward towards the central tropical Pacific Ocean.
- Weaker than normal (easterly) trade winds.
- Low (negative) values of the SOI (Southern Oscillation Index).
More from the Bureau of Meterology on this topic