El Nino predicted for mid-year

Transcript

The National Institute of Water and Atmospheric Research in New Zealand, or NIWA, says an El Nino weather pattern is likely to develop in the Pacific mid-year.

A scientist, Andrew Lorrey, says El Nino occurs every three to seven years, and there are some indications that this year's could be a particularly strong event.

Dr Lorrey says during El Nino, the South Pacific Convergence Zone rainband shifts north of where it usually sits, which can result in changes in rainfall patterns, sea-surface temperature and tropical cyclone occurrences.

He spoke to Mary Baines.

ANDREW LORREY: It's early days right now but the international community has come together to sort of indicate that the probability of an El Nino developing is quite likely at this stage, now whether or not it's going to be a stock-standard, run-of-the-mill El Nino or whether it's going to be a very strong El Nino remains to be seen. There are some indications that it actually could be a quite strong event. Now we haven't had one of those in some time and right now it's just our job to monitor how things are developing in the equatorial region and whether or not that's going to be a likely outcome as we approach say, springtime.

MARY BAINES: So you'll know soon what the possible impacts of this system could be?

AL: Well historically, we are aware of some of the impacts that El Nino brings to small island nations in the Pacific, and we can use that as a guide to what may occur during the coming season, although there's variations from one event to the next.

MB: When was the last El Nino in the Pacific, what impact did it have?

AL: Well we had one a few years ago, and you know, this goes with the cycle of seeing El Ninos and La Ninas on the order of say, every sort of three to seven years, flipping back and forth between La Ninas and El Ninos which bring almost mirror image, opposite conditions to various island nations. With development of El Nino, it changes the regional atmospheric circulation and it helps to do things like move rain-bands which commonly affect certain islands. The rainband is called the South Pacific Convergence Zone, and it also helps to change regional sea-surface temperature patterns, and also things like tropical cyclone occurrences.

MB: Is it too early to say what the potential impacts of this weather could be on specific countries?

AL: It's not too early to say what would occur if an El Nino developed. Typically during El Nino years, for instance, we see this large rain-band called the South Pacific Convergence Zone shift to the north east of where it normally sits. Now it normally sits, if you drew a line over from say the Solomon Islands in a diagonal way, across to Samoa and then the Solomon Islands, that's basically where it sits during, just north of those countries or on those countries during the warm season.  So if it shifts away, it shifts to the north, those areas and those countries, typically end up with drier than normal conditions during El Ninos, during the warm seasons, and places like Tuvalu and Tokelau and the northern Cook Islands end up wetter than normal.

MB: Right. So there could be disruption to food crops or change in sea levels which could affect sea life, things like that?

AL: Well I mean the sea life thing, and the changing of the wind patterns, well yeah I mean it could be quite important for things like entering lagoons. Alternative routes into and out of small lagoons may need to be planned for by people who are fishing, and for goods that need to go in and out of those areas. With regard to other risks in the region, yeah, I mean, some of those countries might see unseasonably high rainfall, which normally sit to the north of the SPCZ, that rainband. And in addition to that, we typically see tropical cyclone activity increase for countries east to the dateline in El Nino years.