Although all the major models indicate that neutral El Nino-Southern Oscillation conditions will persist in the Pacific basin for the next two to three months, there continues to be some variation in them, as is often normal for this time of year.
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The local Australian models, which are often the most conservative, indicate that the neutral conditions will be on the El Nino 'side' of absolute neutrality while American and UK models are already on the La Nina side by mid-June. However, the usual significance of this variation is decreased by the warmer than normal waters which are persisting along the Australian east coast.
Models also vary a little as far as the Indian Ocean is concerned. Most indicate a trend towards a positive Indian Ocean Dipole during winter, although at least the UK model goes for neutrality. This could be important over the next two months, especially as regards the frequency of the prefrontal north west cloud bands which can be responsible for much of the rainfall west of the ranges in NSW and Queensland and north of the ranges in Victoria. The first north west cloud band is crossing Australia at the moment, but the frequency of such events will decrease if the IOD goes more positive.
Most models, however, agree that the IOD will be neutral or even slightly negative by spring, marginally increasing inland rainfall potential at that time. It is worth noting that there is an increasing chance of a La Nina developing in the Pacific by spring and the combination of these two events, coupled with the warmer than normal sea surface temperatures to Australia's east, could see an increase in rain events from all sources during spring and early summer towards the end of this year.
These are the main reasons why there is a better than usual chance that rainfall over most of eastern and south eastern Australia will be above normal between now and the end of the year. However, it must be stressed that such rainfall will be achieved by occasional significant events and these events are likely to be quite patchy. That means there will be extended periods of stable weather in between these events and if a particular area misses out on one or two such events, then significant moisture deficiencies could develop for a while.
Long clear spells will bring strings of cooler than normal nights resulting in average minimum temps ending up close to normal over the next six months. However, daytime temperatures are expected to remain warmer than normal overall, but brief cold spells associated with the infrequent rain events will also occur.
