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. The majority of models predict a return to neutral ENSO during early 2023. La Niña conditions increase the chance of above average summer rainfall in the Southern Cook Islands, and it generally has the opposite effect on the Northern Cook Islands where it tends to get drier. 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 the Northern Cook Islands at the 12-month timescale, Penrhyn is in Meteorological drought while the rest of the N.Cooks (Rakahanga, Manihiki, Pukapuka, Nassau and Suwarrow) have drought watch. At 6-month Penrhyn comes out of meteorological drought but still have drought warning/watch. Pukapuka and Nassau move into meteorological drought, and the remaining islands are still in drought watch. 3-month timescale show Penrhyn, Pukapuka and Nassau still in drough watch/warning respectively and at the 1-month timescale all N.Cooks islands move to No Alert. In the Southern Cook Islands, all S.Cooks islands have No Alert (with the exception of Mangaia in the 12-month timescale only, having a Very Wet Alert) from the 12-months to the 1-month timescale.
Outlook summary: For December, Northern Cook Islands a Dry Alert 3 for all N.Cooks except for Suwarrow with a Dry Alert 1. In the Southern Cook Islands, Rarotonga, Palmerston and Mangaia have Wet Alert 3, 2 and 1 respectively while No Alerts for rest of the S.Cooks islands.
For December 2022 to February 2023, There is a High Chance Dry Alert 3 for Central and all 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, a Low Chance of Dry Alert 1 for Aitutaki and there is a mix of Medium to Low chance of Wet Alert for Mangaia and Rarotonga respectively. No Alert fro remaining S.Cooks islands.(Palmerston, Atiu, Mauke, Mitiaro and Manuae).
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.
Rainfall Outlooks for December 2022, and December to February 2023
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,