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CCA guidance for the Greater Horn of Africa rainfall in Mar-Apr-May 2003 at one month lead

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Outlook
The Greater Horn of Africa (GHA) is defined here as the region between 10°S and 10°N; 25-50°E. For more about the CCA technique, please see description below. The prediction for Mar-Apr-May 2003 GHA rainfall at one month lead (see map below) is weak and calls for climatology across much of GHA. Slightly higher than climatological probabilities for below normal rainfall are predicted for parts of eastern Kenya, southern and northern Somalia, east central and western Tanzania, Rwanda, and Burundi. Slightly higher than climatological probabilities for above normal rainfall are predicted for southern Uganda, and southern Sudan. Although El Nino conditions continued to prevail in January, there were indications that it may weaken within the next few months. The current ENSO event does not seam to influence much this Mar-May 2003 GHA rainfall forecasts.


In this forecast, quasi-global SST between 40°S and 60°N at a resolution of 10° by 10° lat-lon are used to predict GHA rainfall. The predictions are expressed in terms of departures from climatological probabilities for the two extreme categories above and below-normal rainfall. The climatological probability of each of these categories is 0.33. The probability for the normal category remains fixed at 0.33 because CCA has virtually no skill in predicting this category. When skill is low, climatology is suggested. Thus, no forecast is made. The diagnostic data produced by CCA indicate that Mar-May GHA rainfall has a very weak predictability even at 1 month lead.