Heavy Rainfall Associated with the July-August Season over the Central Rift Valley of Kenya
Okoola*, R. E. and Gitau W.* Shilenje**,Z. W. and Camberlin*** P.
*University of Nairobi, Kenya** Kenya Meteorological Department, Kenya*** Climate Research Centre, France
Okoola*, Raphael.E. A.
University of Nairobi, P.O.Box 30197-00100,Nairobi
AbstractTwo rainy seasons are recognized over Kenya. These are the long rainy season March to May (MAM) and the short rainy season of October to December (OND). During these seasons the whole country experiences rainfall. However, over the central Rift Valley, the second rainfall season seems to be missing. This is due to the escarpments over the region with the shift of the short rains such that the July to August rainfall becomes a dominant season. During this season, the heating zone has generally shifted to the north of the equator. Orographic rainfall is generally prevalent during the months of July and August.
Orographic rainfall in the tropics is not common. It occurs mainly in July-August when the dynamic low lies over the region and the escarpments lift the westerly winds over the region bringing with them the moisture laden Congo air mass. They occur during the low pressure season with the plateau lifting the moist air (in the dynamic low) with the ITCZ far to the north of the equator. It is then observed that the moisture laden Congo air is lifted over the escarpments bringing rainfall over the region.
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