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: El Niño near its end. The ENSO Outlook continues at El Niño, but El Niño is weakening and near its end. Oceanic indicators such as tropical Pacific sea surface temperatures have been steadily cooling since December, but are still meeting El Niño thresholds. Atmospheric indicators are now mostly close to neutral ENSO levels.

Climate model outlooks suggest a return to neutral ENSO later in autumn 2024. The ENSO Outlook will remain at El Niño status until this event decays, or clear signs of a possible La Niña appear.

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 March, at 1-month timescale all Northern group islands (Rakahanga, Manihiki, Pukapuka, Nassau and Suwarrow) except Penrhyn experienced Seriously Dry conditions. No extremes were observed for all the Northern Cook Islands at 3, 6 and 12-months timescale. Southern Cook Islands, no extremes were experienced at the 1-month timescale. Very dry conditions for Nga-Pu-Toru (Atiu, Mauke and Mitiaro) at 3-month timescale and no extremes for the rest. 6-month timescale was very dry for Nga-Pu-Toru (Atiu, Mauke and Mitiaro), Mangaia and Palmerston. Very dry conditions continued for all Southern group islands at 12-month timescale with exception for Mangaia and Manuae.

Outlook summary:

For April, Medium chance of Very Wet conditions for Pukapuka, Nassau and Suwarrow and No extreme events for rest of Northern Cook Islands (Penrhyn, Rakahanga, and Manihiki). In the Southern Cook Islands, there is a medium chance of Very Dry conditions for Rarotonga. No extremes expected for the rest (Aitutaki, Mangaia, Palmerston, Manuae, Takutea and Nga-Pu-Toru).

For April to June 2024, no extremes for Penrhyn but a medium to very high chance of Very Wet conditions for rest of the Northern Cook Islands (Nassau, Suwarrow, Rakahanga, Manihiki & Pukapuka). There is a medium chance of Very Dry conditions for Rarotonga, Mauke and Mitiaro, no extremes for the rest of the Southern Cook Islands (Aitutaki, Manuae, Takutea, Mangaia, Palmerston and Atiu).

The outlook suggests Very Wet conditions (associated with the El Niño) are likely to persist over the Northern Cook Islands in the coming months.

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 April 2024, and April to June 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