by Neto Nengomasha – SANF 10 No 37
Southern African climate experts have forecast good rainfall in most parts of the region during the 2010/2011 season.
The rainfall outlook was prepared by climate scientists from national meteorological and hydrological services within the SADC region as well as the SADC Drought Monitoring Centre and the International Research Institute for Climate and Society.
The 14th Southern Africa Regional Climate Outlook Forum (SARCOF 14), which met in Harare, Zimbabwe recently divided the rainfall season into two parts, October-December 2010 and January-March 2011.
Southern and western parts of southern Africa are expected to receive normal to above-normal rainfall in the first half of the season, October-December.
These areas include the extreme western part of the Democratic Republic of Congo, western half of Angola, most of Namibia and the extreme western and north-eastern parts of South Africa, north-western parts of the United Republic of Tanzania.
Southernmost Zambia, north-eastern half of Botswana, extreme north-east of Swaziland, southern half of Mozambique, western parts of Madagascar and the whole of Mauritius and Zimbabwe are also expected to receive the same amounts of rainfall.
Normal to above normal rainfall could be interpreted to mean that the beginning of the rainfall season will be as has been the norm and that as the season progresses the rainfall pattern will be such that it will reach extraordinary levels of above normal.
Areas that are set to have above-normal to normal rainfall are the extreme north-eastern part of Namibia, south-western half of Botswana, the greater part of central South Africa, Lesotho and bulk of Swaziland, extreme south-east Zambia, southern Malawi and most of northern Mozambique.
The greater part of the DRC, eastern half of Angola, most of Zambia, northern parts of Malawi, bulk of Tanzania and extreme northern part of Mozambique and most of Madagascar are likely to receive normal to below-normal rainfall in the same period, October-December.
Above normal to normal could be interpreted to mean that the identified areas will experience more rain at the beginning of the season which will eventually reduce to normal levels as the season progresses.
In the second half of the rainfall season January-March, most parts of the region have increased chances of normal to above-normal with some parts having above-normal to normal rainfall.
Areas include the north-western parts of DRC, southern Angola, south-western Zambia, Namibia, Botswana, Zimbabwe, and the northern parts of South Africa, north-western Swaziland, central Mozambique, southern Madagascar, and Mauritius, the bulk of Tanzania, extreme western Zambia and northern parts of Malawi.
Areas with chances of above-normal to normal rainfall in the same period are the extreme south-western DRC and northern parts of Angola, bulk of Malawi, northern Mozambique and bulk of Madagascar.
However some areas such as southern parts of South Africa, Lesotho, south-eastern parts of Swaziland, southernmost Mozambique, eastern half of DRC, most of Zambia, and western parts of Tanzania are showing some increased chances of normal to below-normal in the second half of the season.
The experts also indicated a high probability of flooding in the Zambezi River Basin during the second half as more rains are expected upstream. Flooding is expected in areas such as Muzarabani, Zimbabwe as a result of some backwash rainfall from Mozambique during the October- December season.
The scientists also took into account that El Nino-Southern Oscillation (ENSO) is in a cold phase that is La Nina, which is projected to persist into early 2011.
El Nino is a weather condition which begins with the warming of the waters in the Western Pacific Ocean and eventually affects the global climate.
The natural warming events alter weather patterns worldwide, probably causing droughts in Southern Africa or contributing to their severity.
The La Nina is an opposite of El Nino where the Pacific Ocean begins with cooler waters than the Indian Ocean and wind moves from the Pacific towards the latter. The occurrence of La Nina results in unusually heavy rains in Southern Africa.
The regional outlook provides a first case of the seasonal outlook process which then requires downscaling by national meteorological departments before it can be finalised.
Users are therefore strongly advised to contact the National Meteorological and Hydrological Services for interpretation of what normal to above-normal would mean in terms of rainfall amount, when to plant, updates and other additional guidance.
It is also relevant only to seasonal timescales and relatively large areas and may not fully account for all factors that influence regional and national climate variability, such as local and month-to-month variations.
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