In its latest Island Climate Update, New Zealand’s National Institute of Water and Atmospheric Research (NIWA) said the tropical Pacific was borderline between neutral and El Nino conditions last month.
“Sea surface temperatures continued to increase in the central and eastern Pacific. Chances for El Nino over the June-August 2014 period are about 60 per cent.”
It said the chances for El Nino increase over the following seasons, reaching 72 per cent in November to February.
“Uncertainty remains about the strength of the event if it does fully develop.”
The current forecast is for normal or below normal rainfall for the northern Cook Islands between June and August, and near or above normal rainfall for the southern Cooks.
El Nino is a pattern characterised by unusually warm ocean temperatures in the Equatorial Pacific, bringing dry weather, and potential drought and tropical cyclone conditions.
Arona Ngari, Director for the Cook Islands Meteorological Service, said if El Nino does arrive, the Southern Cooks could be in for a dry year run.
“Our rainfall normally diminishes by up to 60 per cent, so instead of us getting our normal 700mm for the winter, we probably get half or less than half. During the summer months the normal 1300mm reduces by up to 50 and 60 per cent.”
El Nino also usually means the risk of tropical cyclones increases for the Cook Islands, Ngari said.
Winds tend to blow consistently from the south-east.
Ngari said the country has been in a “neutral” phase for the last six months, which often precedes an El Nino.
As for this weekend, Ngari said there could be more rain to come, depending on where the current low pressure system tracks. People in the Southern Cooks should expect strong southeast winds.