This outlook is based upon the Dec 2017 to Jan 2018 NINO3.4 SST Anomalies extended (NINO3.4 SST Anomalies)
Rarotonga 3mth (Mar to May 2018) Rainfall outlook. Based upon the 2mth Average value of the NINO3.4 SST Anomalies during Dec 2017 to Jan 2018, the forecast is biased towards "above-normal" Rainfall conditions for March through to the end of May for Rarotonga, with a forecast probability of 42%. The chance of "below-normal" Rainfall occurring is 24% while the chance of "normal" Rainfall is 34%.
Another way of looking at this, is that given the current climate conditions, in about 4 out of every 10 years, the Rainfall in the March-May period are expected to be "above-normal"; about 4 out of 10 years are expected to be "normal"; and about 2 out of 10 years are expected to be "below-normal".
"Below-normal" Rainfall for the March to May period at Rarotonga includes Rainfall less than 515.4mm.
"Above-normal" Rainfall is that which is greater than 653.7mm.
"Normal" Rainfall lies between 515.4 and 653.7mm.