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.

Current El Niño-Southern Oscillation (ENSO) status:

The ENSO Outlook remains at 'La Niña Watch', meaning there are some signs that a La Niña might form in the Pacific Ocean later in 2024.

Cook Islands Meteorological Services along with regional climate partners will continue to closely monitor conditions in the tropical Pacific as well as model outlooks for further developments.

Status summary:

In August, Very Wet conditions were observed over Penrhyn and Very Dry conditions were observed over Atiu and Takutea.
From June to August, Very Wet conditions were observed over Rakahanga, Manihiki and Penrhyn. Very Dry conditions for Rarotonga.
From March to August, all Southern group islands except for Mitiaro and Mauke, experienced Very Dry conditions.
Palmerston, Takutea and Atiu were in meteorological drought at the 12-month timescale. Whilst Rarotonga, Mangaia, Aitutaki, Mauke and Mitiaro experienced Very Dry conditions.

Outlook summary:

For September, there is a medium chance of Very Dry conditions for Penrhyn. Medium chance of Very Wet conditions for Manihiki, Pukapuka, Nassau, Suwarrow, Palmerston, Aitutaki, Manuae, Takutea, Atiu and Mitiaro. High chance of Very Wet conditions for Rarotonga, Mangaia and Mauke.

For September to November 2024, there is a high chance of Very Dry conditions for Penrhyn. A medium chance of Very Dry conditions for Manihiki and Rakahanga. A medium chance of Very Wet conditions for Suwarrow, Rarotonga, Mangaia and Mauke.

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

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 be impacted. Note the periods are estimates only. Allow for uncertainty associated with island size, topography, and 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

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.

Extreme Rainfall Outlooks

Rainfall Outlooks for August 2024, and August to October 2024

About Rainfall Outlook

Seasonal outlooks have been produced using the Australian Bureau of Meteorology ACCESS-S model http://www.bom.gov.au/climate/ahead/about/model/access.shtml. 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,

Website: http://www.met.gov.ck Email: mot.weather@cookislands.gov.ck