THE development of an El Nino is still favoured to occur during spring, although the rate of cooling in the sea surface temperatures in the critical areas of the tropical eastern Pacific has slowed down in the past couple of weeks.
The consensus from international models now puts the chance of this development at around 50 per cent - slightly lower than a week or two ago, so this is one slightly optimistic feature.
However, near El Nino conditions are still likely to negatively impact on eastern Australian rainfall in the coming months.
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As indicated previously, past El Nino events resulted in lower than average spring and early summer rainfall in NSW in about 70pc of the cases, meaning that this is not always the case.
However, on this occasion, we are coming off a period of autumn and winter with already established quite severe moisture deficiencies so the need for rectification will require well above average rains which appear most unlikely this year.
A potential El Nino and warm SSTs around continental Australia both point to a high chance of above average temperatures in spring.
Cloud cover in the “heat engine” area of north-western Australia is already very low and higher than normal temperatures will periodically spread into the south-eastern states with increasing frequency during spring.
Weak or establishing El Nino events in the past have often been associated with a slight increase in severe storms, meaning that hail potential in mountain areas and in the north-east of the state is slightly higher than normal in the second half of spring and early summer this year.
Many models also indicate that the currently neutral temperature patterns in the Indian Ocean, as indicated by the Indian Ocean Dipole (IOD), might become a little cooler in coming months reducing the chances of this area “helping out” with rain events in the south-east of the country in spring.
They will have little or no effect on our weather in summer.
