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Cook Islands Meteorological Service

Early Action Rainfall Watch

The Early Action Rainfall Watch provides sector managers with a brief summary of recent rainfall patterns, particularly drought and the rainfall outlook for the coming months.

ENSO Status - Latest

Current El Niño-Southern Oscillation (ENSO) status: The ENSO Outlook remains at LA NIÑA as the event continues to slowly weaken. Most models show a return to neutral El Niño–Southern Oscillation (ENSO) over June to August. When La Niña is present the Northern Cook Islands are likely to be drier than normal and the Southern Cook Islands are likely to be wetter than normal. CIMS office will continue to closely monitor conditions in the tropical Pacific as well as model outlooks during this La Niña event.

Status summary: The Northern Cook Islands are largely in Meteorological Drought at the 12-month, 6-month, and at the 3-month timescale (Pukapuka and Nassau in drought watch at the 6-month timescale). At the 1-month timescale, Pukapuka and Nassau remain in Meteorological Drought. In the Southern Cook Islands Palmerston is in Drought Watch and Mangaia has a Very Wet status at 12-month timescale, then at 6-month timescale, Aitutaki joins Palmerston in Drought Watch and Mitiaro, Mauke and Atiu and Mangaia have a Very Wet status. At 3-month timescale all stations is in Meteorological Drought except for Rarotonga and Mangaia and at the1-month timescale only Nassau and Pukapuka up north are in Meteorological drought.

Outlook summary: For June, there is a High Chance Dry Alert for the four northernmost Cook Islands, medium chance dry for Nassau, and a Medium or High Chance Wet Alert for Palmerston, Aituaki and Rarotonga.

For June to August 2022, follows a similar June pattern where there is a High Chance Dry Alert for the Northern Cook Islands (Penrhyn, Rakahanga, Manihiki, Pukapuka, Nassau and Suwarrow). The outlook is for the long term drought to continue in the coming months. In the Southern Cook Islands, there is a Medium to High Wet Alert for the Southern Cook Island stations except Mauke, Atiu and Mangaia.

See table/maps below for additional information. See status table below for potential impacts.


After the specified period of below or above average rainfall, the following primary agricultural and hydrological variables and secondary socio-economic and health variables may to be impacted. Note the periods are estimates only. Allow for uncertainty associated with island size, topography, geology and soil type. Contact the relevant sector offices for further information on impacts.



Rainfall monitoring for 12-month, 6-month, 3-month and the past month

12-Month Monitoring Map


About Rainfall Monitoring

The Standardized Precipitation Index (SPI) is used to assess rainfall status from the MSWEP dataset. MSWEP is a global precipitation product that combines rain gauges, satellite and reanalysis data to a 0.1° resolution. Meteorological Drought is defined as drought assessed by rainfall data only. A site is assigned 'No Alert' when rainfall has been near normal for the period(s) in question. The 3-, 6- and 12-month timescales can accurately predict drought, whereas 1-month status is an approximation only. This is because it is difficult to assess drought at this timescale.



Rainfall Outlooks for March 2022, and March to May 2022

Outlook Maps


About Rainfall Outlook

Seasonal outlooks have been produced using the Australian Bureau of Meteorology ACCESS-S model The outlook provides an indication of total one and three-month rainfall, not how intense the rain may be in any one event, nor how it may vary within the three months. A station is assigned 'No Alert' when near normal rainfall is favoured or there are equal chances of below normal, normal and above normal rainfall.


Contact the Cook Islands Meteorological Service for further information

The Director, Cook Islands Meteorological Service

P.O Box 127, Rarotonga, Cook Islands, Phone: 682 20603,

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