El Nino is reaching peak intensity.
As expected, the 2015 El Nino is now close to its peak intensity in the tropical Pacific Ocean. It has recently reached comparable levels in the tropics to the 1982/83 and 1997/98 events.
MetService and Federated Farmers have been working together since April, providing information about likely El Nino development and what typically happens during El Nino events here in New Zealand.
MetService meteorologists continually assess what is happening locally, in order to produce the monthly forecasts at http://www.metservice.com/rural/monthly-outlook.
We know that not every El Nino behaves in the same way here in New Zealand, simply because local climate drivers (the Tasman Sea or the Southern Ocean) can either reinforce or diminish El Nino effects. In other words, short-term weather can 'trump' longer-term climate! At the current time, we are also monitoring the Indian Ocean and Australia carefully, since conditions there may have down-stream implications for us into 2016.
Many farmers and growers are now seeking information about what happened during the previous 'super' El Nino events of 1982/83 and 1997/98, to serve as an initial reference as to 'how bad was it last time'. While this is useful for understanding possible effects, there is no guarantee that the climate in the first half of 2016 will unfold in the same manner as was seen in either 1983 or 1998 - so please keep tabs on our monthly commentary.
The observed climate seen in New Zealand during 1982/83 and 1997/98 El Nino events differed over the summer (December to February).
Summer 1997/98 was strongly anticyclonic, with prevailing high pressure over the North Island, and frequent west to northwest winds over the country.
In comparison, the summer of 1982/83 was stormy, with frequent lows and southwest winds over New Zealand. Not surprisingly, summer 1997/98 was unusually hot for many North Island and eastern regions, while summer 1982/83 was unseasonably cold across the country.
However, northern and eastern areas of the country recorded dry summers in both events often with less than 50 per cent of summer rain observed.
Wellington was also rather dry. The southwest of the North Island was in somewhat better shape, with closer to normal rainfall through summer and autumn.
For locations in the south and west of the South Island, such as Invercargill and Milford Sound, both El Nino events delivered an extended wet period (summer and autumn).
Importantly, the largest El Nino impacts occurred in the regions that could least afford it. Namely, the eastern regions which typically experience low summer rainfall totals: Bay of Plenty, Taupo, Gisborne, Hawkes Bay, Wairarapa, Marlborough and Canterbury.
Notably, large differences were seen in autumn rainfall between the events. Autumn 1983 saw healthy rains return across the South Island, but it remained drier in the northeast of the country. In comparison, autumn 1998 was relatively dry across the entire North Island, and particularly so for the east coast. The eastern South Island also continued somewhat drier, too. The prolonged dryness through autumn 1998 was effectively the straw that broke the camel's back. The autumn of 2016 may well prove critical, too.