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 event persists. Climate model outlooks suggest El Niño is at or near its peak, with the event likely to weaken over the coming months, returning to neutral in the southern hemisphere autumn 2024. The ENSO Outlook will remain at El Niño status until this event decays, or signs of a possible La Niña appear.
El Niño typically leads to reduced amounts of rainfall for Rarotonga and the Southern Cook Islands. The opposite is true for Penrhyn and the Northern Cook Islands, which typically gets more than normal amounts of rainfall. Warmer days are expected as well. 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 December, no observed extremes for the Northern Cook Islands. Wet conditions were observed for Manihiki at the 3 and 6-month timescale, but dry conditions were observed for the Northern Cook Islands (Penrhyn, Rakahanga, Pukapuka, Nassau and Suwarrow) at the 12-month timescale. It was a dry December for the Southern Cook Islands (Aituaki, Atiu, Mangaia, Mauke, Mitiaro and Palmerston), and it continued for the 3 – 6month timescale. No extremes were observed for the 12months timescale.
For February, a medium to high chance of Very Wet conditions for all Northern Cook Islands (Penrhyn, Rakahanga, Manihiki, Pukapuka, Nassau and Suwarrow) is expected. In the Southern Cook Islands, there is a medium chance of dry conditions for Aitutaki. Also there is a medium chance of wet conditions for Rarotonga, Mangaia, Manuae, & Takutea.
For February to April 2024, medium to high chance of Very wet conditions for all Northern Cook Islands (Penrhyn, Rakahanga, Manihiki, Pukapuka, Nassau & Suwarrow). There is a low to medium chance of Very Dry conditions for Aitutaki, Mangaia and Nga Pu Toru (Atiu, Mauke & Mitiaro)
The outlook suggests Very Wet conditions are likely to persist over the Northern Cook Islands in the coming months.
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 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 February 2024, and February to April 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,