Summer droughts forecast in strong El Niño conditions

Nuku'alofa, Tonga

Summer rainfall in Tonga is expected to be severely diminished with only half the expected monthly rainfall in some places, Tonga's Meteorological director warned today, after assessing the latest El Niño forecasts.

'Ofa Fa'anunu advised people to conserve water as drier than normal conditions are forecasted for the next three to six months in Tonga.

“This year's El Niño is now the strongest since the 1997/98 event (which caused severe drought -the third driest on record in Ha’apa,i and Tropical Cyclone Waka in Vava'u). The big event before that was the 1982/83 El Nino, which caused the driest year on record throughout Tonga (1983) and Tropical Cyclone Issac,” he said.

“Up to now, as with previous El Nino years, Ha’apai and Tonga have received above average rainfall, which is expected, but up north from Vava'u to the Niuas the dry conditions are already being experienced.”

In a public advisory on September 10 Tonga's Meteorology Division reported that the Pacific Ocean and atmosphere had sea surface temperatures well above El Niño thresholds. El Niño is the movement of warm ocean water from the north of Australia to South America crossing the Pacific Islands every three to seven years, changing weather patterns.

The current situation is that Niuafo’ou recorded the highest maximum day time temperature of 30.0°C on 1 August and the lowest night time minimum temperature was 12.0°C on 17 August in Fua’amotu, Tongatapu.

Rainfall received across the country during August was normal over the Niuas and wetter than normal throughout Tonga.

Rainfall in the last three months of June-August was below normal in the Niuas and Vava’u, normal in Ha’apai and Fua’amotu and above normal in Nuku’alofa.

Meanwhile, from August 8-12 rainfall eased the dry conditions experienced as more than 100mm rainfall received in 24-hours in Tongatapu, Ha’apai and Vava’u.

However, rainfall foreast for the next three to six months continues to favour drier than normal conditions for Tonga. Communities are advised to collect as much water as possible because this pattern of three month outlook is typical El Niño years.

The islands with rainfall deficiencies are likely to intensify in the current dry season from May-October, while below normal rainfall are favoured into the wet season, November-April.

The Meteorological Office will be issuing El Niño updates every two-weeks from now to get the message across, said 'Ofa.

Cooler nights

For Tonga, El Nino usually brings cooler night time temperatures from May to October, less rainfall and more cyclones than usual.

El Nino years are excellent for growing sweet potatoes (provided enough water is given) and crops that depend on cooler night time temperatures but it not good for rain dependent crops in the summer time.

Fruit trees and vanilla also tend to do well during El Nino due to stress induce flowering while tuna fisheries on the other hand tends to be poor due to tuna stocks migrating away from Tonga waters.

El Nino