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 El Niño Alert. When El Niño Alert criteria have been met in the past, an El Niño event has developed around 70% of the time. Central and eastern Pacific sea surface temperatures are exceeding El Niño thresholds. While the oceans have shifted towards El Niño thresholds, sustained wind, cloud and broad-scale pressure patterns continue to reflect an ENSO neutral state. This means the Pacific Ocean and atmosphere are not fully coupled, as occurs duringElNiñoevents. Cook Islands MeteorologicalServices along with regional climate partners will continue to closely monitor conditions in the tropical Pacific as well as model outlooks for further developments.
For July, there is a medium to high chance of Very Dry conditions for all islands except Palmerston, Manuae, Mitiaro, Mauke and Atiu where there is a low chance of extremes.
For July to September 2023, there is a medium to high chance of Very Dry conditions for all islands except Manuae, Mitiaro, Mauke and Atiu where there is a low chance of extremes. Chances are highest for the Northern Cook islands, particularly around Suwarrow and Palmerston.
The outlook suggests Very Dry conditions may develop over the Cook Islands in the coming months, with chances highest over the Northern Cook Islands.
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 July 2023, and July to September 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,