Climate of Rarotonga – spring [Sep-Oct]
The weather and climate in Rarotonga is largely dependent on the position and the intensity of the South Pacific Convergence Zone [SPCZ]. This is an area of cloud band that migrates north and south with the seasons, when during the wet season it moves south to bring above normal rainfall over the Southern Cooks and during the dry season moves north to bring above normal rainfall for the Northern Cook Islands.
Another climate driver that have an influence on the weather and climate of Rarotonga are what meteorologist calls east west moving subtropical ridges [STR] on weather maps they are high pressure systems that passes to the south or over Rarotonga during the winter and spring of every year. These STR’s tends to bring cold air masses from the south enhancing cool temperatures over Rarotonga and if the air pressure within them increases to 1030hectopascals it can bring strong southeast trade winds that can be persistent for days and weeks.
There are two dominant seasons for the Cook Islands a wet season also the Tropical Cyclone Season [November to April] where 2/3 of the rainfall are recorded and a dry season [May to October] where 1/3 of the rainfall are recorded.
Rarotonga climate and weather can also be classified in to the four seasons based on the distribution of minimum and maximum air temperatures. That is November to April [summer], May to June [autumn] July to August [winter], and September to October [spring]
During the spring of this year 2010 mean temperatures range from 21.8°C to 23.5°C, indicating a warmer spring in comparison to 2009 where mean temperatures ranged from 20.6°C to 22.1°C and based on the last 5yrs of spring the mean temperatures of 2010 was much warmer. Most of us would have also noted that our winter months of July and August were not as cold as compared to 2009 even though we experienced a few nites and early chilly mornings. The coldest spring month in the last 5yrs was in 2005 where minimum temperatures range from 12.5°C to 17.1°C compared to 2010 for the same time 18.0°C to 19.9°C.
Now with the onset of the summer period and the end of the spring the temperatures are expected to become warmer and therefore less cold nights. The spring months in terms of sunshine and day-light hours are also known as the “Equinox Season” This is when the nights and daylight hours are almost the same. These changes occur as the earth slowly tilts towards the sun for the southern hemisphere and away from the sun for the Northern Hemisphere, and therefore the season changes. The spring season is also called the transitional period from cold to warm and sometimes these transitional months can bring about the bout of common flu.
We can also experience a good amount of rainfall during the spring as monthly total rainfalls can exceed the normal 100mm a month or about 4inches of rain. The outlook for this spring is for warmer temperatures and average rainfall as we head towards our summer season.
Cook Islands Meteorological Services
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