El Nino weather system looks set to develop
There could be more dry weather on the way as El Nino conditions look more likely to develop in the Pacific in winter, with recent forecasts suggesting it could be a particularly intense event.
For New Zealand, El Nino usually means stronger or more frequent winds from the west during summer, often leading to drought on the east coast and more rain in the west of the country.
In winter the winds tend to come from the south, bringing colder temperatures.
In the lead up to an El Nino event, warm water spreads from the west Pacific and the Indian Ocean to the eastern Pacific, often pushed by a reversal of the trade winds as is happening at the moment.
In El Nino years there are more floods and droughts, especially in countries around the Pacific Rim, which affects global commodities.
Lower rainfall in the west of the Pacific would probably deepen drought conditions already being experienced in Australia affecting beef production. It would also affect crops across Malaysia and particularly rice crops in Thailand and the Philippines, along with cocoa and coffee production in Indonesia and Vietnam.
It can also lessen the amount of rain in monsoons in India, but cause flooding in southern China
Off South America there is likely to be less upwelling of nutrients from the deep sea, which will see less food available for fish stocks with a flow-on effect for fishing.
But the large amount of warm water lying below the ocean surface is fuelling speculation this El Nino could be particularly strong if it comes to the surface and starts affecting the atmosphere, perhaps as intense as the destructive 1997-98 event.
In an update this week, the Australian Bureau of Meteorology put the likelihood of El Nino developing in the next few months around 70 per cent, with US meteorological agency NOAA putting it at a 50 per cent probability.
There is no certainty yet, National Institute of Water and Atmospheric Research (Niwa) principal scientist Dr Brett Mullan says.
This time of year is when modelling is the least precise, so the weather system may fizzle out yet, he says. It will probably be another month before it becomes clearer what's happening.