The tropical Pacific Ocean is in a neutral El Niño-Southern Oscillation (ENSO) state. In the following section ‘neutral’ means - neither in El Nino nor in La Nina. The ENSO is a major climate driver that influences rainfall, temperature and sea level patterns across the Pacific.
Sea surface temperatures across the tropical Pacific have been at neutral levels for the past four weeks, with the central Pacific Ocean having recently cooled to levels close to normal.
Temperatures below the ocean surface are now largely cooler than normal. In the atmosphere, indicators of ENSO such as the trade winds, cloudiness near the Date Line, and the Southern Oscillation Index (SOI) are at neutral levels.
The Southern Oscillation Index (SOI) is an index used by Met Officers to track ENSO. Sustained positive SOI values above about +8 indicate a La Niña event while sustained negative values below about –8 indicate an El Niño. Currently it’s near zero which is neutral territory.
What this means for the Pacific island region
- Below or well below normal rainfall experienced over five of the past six months in Niue, New Caledonia, Southern Cook Islands. Below normal rainfall is forecast over the next three months in Niue, normal or below normal rainfall is forecast in the Southern Cook Islands and near normal rainfall is expected in New Caledonia.
- Below or well below normal rainfall experienced over four of the past six months in the Federated States of Micronesia. Below normal rainfall is forecast over the next three months.
- Below or well below normal rainfall experienced over three of the past six months in Fiji and Vanuatu. Below normal rainfall is forecast over the next three months.
- Drier than normal conditions over some of the Pacific island countries may continue coinciding with the dry season. Every effort should be made to mitigate the impacts of this over the course of the next few months to ensure climate-sensitive sectors are not severely impacted.
Raised sea levels were present north and south of the equator in the central and eastern tropical Pacific. In the northwest tropical Pacific they exceed +30 cm. Around Fiji, Samoa, Solomon Islands and Tuvalu sea levels were lower than average with small regions below -10 cm and a patch, below -15 cm north of Fiji. Lower sea levels can expose corals to the elements and may cause bleaching.
Rainfall outlook for the southwest Pacific for the June - August 2016 period. Source: ICU