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El Nino Advisory No.1 for Tonga

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08th August 2014 English|Tongan An El Niño Watch is now in force for Tonga



Based on the global climate models and assessments of the Tonga’s current climate regime there is at least a 50% chance of a El Niño developing by September or October 2014. The effects of El Nino on Tonga usually include cooler night time temperatures, lower rainfall during the rainy season, and more tropical cyclones.


What is El Nino?

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 usually results in changes in weather and climate. El Nino is a natural occurrence and happens about every 3 to 7 years.


Current Situation

The tropical Pacific Ocean surface temperature is currently at levels typically associated with a weak El Niño with warming seas surface temperatures in the Pacific since the beginning of the year to about April. Although there has been cooling of the ocean temperatures in the Pacific in the last 2 months, rainfall has persisted into the dry season in Tonga and night time temperatures have been cooler than normal. These are usually the indicators that an El Nino is on the move. However, continued warming of the Pacific Ocean and further drop in the trade winds would need to take place and to persist in the next 1 to 2 months in order to confirm beyond doubt that an El Niño has developed or will continue to develop.


Effects of El Niño on Tonga’s Climate

El Niño 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 1 cyclone per year but increases to around 2 during El Nino.


Major El Nino Events in recent history

The worst droughts to be recorded in Tonga in recent history happened during El Nino Years. The 1982-83 and the 1997-98 caused water shortages to a point where water had to be distributed to the islands of Ha’apai and caused food shortages as a result of devastation to Agriculture. Tropical Cyclone “Isaac” (Category 4 Cyclone that affected most of Tonga Islands and most costly on record) and Tropical Cyclone “Ron” (Category 5 Cyclone, strongest ever recorded in Tonga’s history affected Niuafo’ou) occurred in 1982 and 1997 respectively.


Effects of the 1982/83 & 1997/98 El Nino on Tongan Rainfall

Tongatapu 1982/83

Ha’apai 1997/98

Figure 1: Shows rainfall was severely reduced during the raining seasons of 1983 and 1998 in Ha'apai and Tongatapu.                  This effect was attributed to the 1982/83 and 1997/98 El Nino.

What is likely to happen in 2014/15 if El Nino develops in September/October 2014

If El Nino fully develops to the scale of the 1982/83 and 1997/98 events which looks unlikely at this stage, then the rainfall regime may start to become very dry towards the end of 2014 and throughout the first half of 2015. This could mean severe water shortages towards the middle of 2015. Tonga could also expect more cyclones than normal in the 2014/15 cyclone season starting in November 2014. The more likely scenario at this point in time taking into account the current ocean and climatic conditions is for a short-lived El Nino event like the 1993 event. The present conditions are similar to that of 1993. The rainfall regime of 1993-1994 is shown here as an indicator of possible rainfall regime Tonga could expect in the coming months. It shows that during the short lived El Nino of 1993/94 there were drought conditioned that were experienced especially during the rainy season with the worst drought of 8 months in experienced in Ha’apai from about October 1993 to May 1994. Similar conditions could happen in 2014/15.

Figure 2: Present ocean and atmospheric conditions closely resembles the 1993 conditions. In 1993/94 Tonga experienced some drought conditions over the rainy season with the worst drought of 8 months from October 1993 to May 1994 in Ha’apai.

3. Tropical Cyclones also occurred in Tonga in the 1993/94 cyclone season (TC NINA-Hurricane, TC KINA- Hurricane and TC MICK- Storm) in January and February. 2 of those became hurricanes.

Recommended actions for the next 3 months

Planners are encouraged to be on the alert for a possible El Nino development in the coming 3 months. Rainfall and tropical cyclone sensitive sectors such as Agriculture and Fisheries (Food Security), Health, Water Resource Management and Tourism should start to pay attention and follow closely the climate outlooks in the next few months.

The public are encouraged to start seeking advice from the relevant authorities e.g. Ministry of Agriculture and the National Emergency Management Office (NEMO) on the best practices to minimise the effects of El Nino.

Citizens are also encouraged to follow the El Nino Advisories over the coming months issued by the Meteorological Service. The next El Nino Advisory will be issued in early September 2014.

Contact & Further information

For further information contact the Meteorology Division of the Ministry of Environment, Energy, Climate Change, Disaster Management, Meteorology, Information and Communications at Telephone 35355 or Email This e-mail address is being protected from spambots. You need JavaScript enabled to view it . More information is also available at www.met.gov.to



Issued by the: Ministry of Environment, Energy, Climate Change, Disaster Management, Meteorology, Information & Communication, P.O. Box 1380, Level 2, O.G Sanft Building, Nuku'alofa, Tonga. Tel: (676) 28170 Fax:  (676) 24861; Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it , Websites : www.tongaportal.gov.to

Last Updated ( Friday, 08 August 2014 15:44 )  

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