Cool nights and low rainfall for August indicates that Tonga may be affected by a climatic conditions known as “El Nino” with the potential of droughts occurring in the coming months.
A national weather advisory released yesterday stated that there is a 50% chance of an El Nino developing in Tonga in the coming months, and an El Nino watch remains in force.
“The effects of El Nino usually include cooler night time temperatures, lower rainfall and more tropical cyclones,” stated the advisory issued by the Tonga Meterorological Service.
El Nino is the movement of warm ocean water from the north of Australia to the South American coast along the tropics. It brings warmer than normal water to the central and eastern tropical Pacific, which usuallly results in changes in weather and climate.
“El Nino events normally last for around a year; however they can be shorter, or last much longer depending on the nature of the event. The effects of El Nino on Tonga usually varies but for most of the time it brings cooler dry seasons (like we are experiencing now) and drier wet seasons than normal and more cyclones. Usually Tonga is affected by one cyclone per year but it increases to around two during El Nino.”
The advisory stated that if an El Nino were to occur, severe water shortages would occur towards the middle of 2015. It encourages rainfall sensitive sectors to follow El Nino advisories. Water conservation is advised across the whole of Tonga as below normal to normal rainfall is the most likely outlook across the country in the next three months.
The observed rainfall for August has been very low in Tongatapu and below normal for Vava'u, Ha'apai and Niuafo'ou except for Niuatoputapu wher it received above normal rainfall.
El Nino is a natural occurrence and happens about every three to seven years.
The worst droughts to be recorded inTonga happened during El Nino years in 1982-83 and 1997-98 cause dwater shortages to a point where water had to be distributed to the islands of Ha'apai and caused food shortages.
Tropical Cyclone Isaac (Cat 4) in 1982 and Tropical Cyclone Ron (Cat 5) in 1997 occurred during El Nino years.