All medium and long term climate indicators have shown minimal change in the last couple of weeks and there is no reason to alter any summer prognosis at this stage.
A weak “El Nino” will not have significant effect as moisture availability continues to be helped by above average sea surface temperatures, especially in the tropical western Pacific.
Consequently, the main effects of the developing El Nino will ensure that overall summer temperatures are warmer than normal although the prolonged and sometimes extreme heat of last summer is not favoured to be repeated.
The Southern Oscillation Index (SOI) continues to hover around zero or the middle of the neutral range.
This indicates that the atmosphere is not necessarily linked to the ocean patterns (the latter being more indicative of an El Nino.)
This is another factor to support the scenario favoured by me that the effects of this summer’s El Nino will be minimal.
There are one of two slightly worrying features.
The development of the wet season in the north has been delayed and there has been little significant rain in the tropical areas of the country in the last month.
The other slight concern has been the cooling of sea surface temperatures in the Indian Ocean and although the effects of the Indian Ocean temperatures are minimal over the summer months, this – linked to a late development of the monsoon, means moisture availability from this source will be lacking for at least the first half of summer.
The longer term outlook remains clouded. There is little doubt we are entering “uncharted waters” with sea surface temperature world wide at higher levels that have been in recorded history.
Global warming – whatever the causes – is continuing and its effects are far from clear. In 2019, it is likely to mean a neutral year for much of Australia.
Indications are that it will be warmer than normal (for the majority of the months) and that overall rainfall in the eastern states will end up close to or slightly up on normal but significant rain is required to overcome the deficiencies already established and unfortunately, such events might be few and far between.
The best chance of rain events will be during autumn in the east and NE of NSW and Queensland and early winter in southern NSW and Victoria.
So, there’s a 55 per cent chance of rainfall reaching normal in the east in autumn and a 45 per cent chance in the south.
