Possibilities to forecast early summer rainfall in the Lesotho Lowlands from the El-Niño/Southern Oscillation

Abstract

Lesotho is located approximately at latitude 30°S in the interior of Southern Africa. The mesocale climate is complicated and governed by various weather systems. The inter-annual rainfall variability is great, resulting in low food security, since the growing of crops is almost exclusively rain-fed. Reliable forecasts of austral summer rainfall, especially early summer rainfall (October-December), are thus valuable. Earlier research has shown that the El Niño/Southern Oscillation signal from the Pacific can be discerned in Southern Africa. In general the signal from the El Niño/Southern Oscillation is strongest in the later part of the early summer. October, November and early summer rainfall are significantly correlated with certain preceeding values of the Southern Oscillation Index (SOI), but weakly so. December rainfall and aggregate November-December rainfall are significantly correlated fairly strongly (r = 0.5 approximately) with certain preceeding SOI values. Lead times of four months seem to be attainable.

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