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Africa: Drought and floods hazards assessment: 10 Sep 2003

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CCA Guidance for East Africa Rainfall in Sep-Nov 2003 at One Month Lead

East Africa is defined here as the region between 5°N and 10°S; 30-50°E. The prediction for Sep-Nov 2003 East Africa rainfall at one month lead (eafson1.gif) is weak and calls for climatology across the region, except the area that encompasses northwest Kenya, northern and western Uganda, and eastern Rwanda, where slightly higher than climatological probabilities for above normal rainfall are predicted. The neutral state of ENSO and weak sea surface temperature anomalies across the Atlantic and the Indian Ocean suggest uncertainty in the forecasts for the next few months.

The diagnostic data produced by the Canonical Correlation Analysis indicate that Sep-Nov East African rainfall has a modest predictability at 1 month lead.

Over the continent, very heavy rains struck northeastern Ghana, Togo, Benin, parts of Nigeria and much of Cameroon (100-200+ mm). The heavy rains resulted in areas of flooding, with severe flooding reported along the Kuduna River in Nigeria. Heavy rains also fell across eastern Senegal (75-150+ mm). Widespread seasonal rains (40-120 mm) fell across southeastern Mauritania, southern Mali, Burkina Faso, southwestern Niger and northern Cote d'Ivoire. Showers and thunderstorms prevailed across Guinea-Bissau, the Gambia, western Senegal and southwestern Mauritania. Powerful storms rocked parts of northeastern Algeria with heavy rains and damaging winds. Showers were on the increase across central Cote d'Ivoire and Ghana as the second wet season sets in, with only spotty showers further south. Locally heavy rain fell across southern Liberia on the 2nd and 3rd of September. Heavy rains across CAR caused flooding the northeastern town of Sibit. Further east, heavy rains (50-150+ mm) fell across the highlands of Eritrea, western Ethiopia, and across southeastern Sudan. By contrast, rainfall was fairly light across the eastern and southern highlands of Ethiopia. In the south, a frontal system produced showers across southern Mozambique, eastern South Africa and Lesotho. Some of the rainfall in Mozambique was heavy.

NOAA/CPC,USGS






AFRICA WEATHER HAZARDS ASSESSMENT EXPLANATION VALID September 11-17, 2003

1) Although rainfall during the past month has helped to relieve dryness in much of northern Senegal and southern Mauritania, conditions remain unfavorable toward extreme northwestern Senegal. During the past week, rainfall totals locally greater than 50 mm were noted in parts of southern Mauritania and widespread totals exceeding 100 mm were seen in eastern Senegal. Much of this precipitation fell outside the area of concern however, though latest forecasts indicate a chance for more rainfall during the next week.

2) Saturated soil conditions and heavy rainfall is leading to areas of flooding in parts of eastern Burkina, northeastern Ghana, northern Togo, northern Benin, and western Nigeria as daily showers and thunderstorms continue to move over the region. Flooding seen near the Kaduna state in north central Nigeria may be increased by additional rains during the upcoming week. The past week's local rainfall totals exceeding 200 mm in Ghana were similar to totals seen along the southern Nigeria / Cameroon border where flooding problems will also occur.

3) Heavy rainfall, primarily on September 3rd, fell over parts of southwestern Eritrea and caused flooding in the region. To the south along the Ethiopia border, widespread weekly rainfall totals exceeding 50 mm were seen, with local totals up to 200 mm. The latest rainfall forecasts along with soil moisture model outputs suggest the flooding threat to continue.

4) Little precipitation fell over drought affected areas of northern Somalia during the last week, though some light showers or thunderstorms are possible through the next 7 days. Dryness continues in this area due to poor performing rains during the last season.

5) Erratic and somewhat lighter than normal rainfall continues over parts of southern and southeastern Ethiopia, although very heavy rains were seen during the past week in areas of southeastern Sudan. While these rains have helped to remove dryness from the westward most part of the hazard area, spotty areas of dryness continue throughout the remainder of the region. Latest forecasts predict up to 40 mm of rainfall to occur in the area during the next 3 days, so this should further help to alleviate dryness.

6) Localized flooding continues near and along the Nzoia river in western Kenya near Lake Victoria. Past 7-day rainfall accumulations of greater than 125 mm in the area have kept river levels at bankfull conditions and additional precipitation is expected during the next week.

7) Up to 30 mm of rain was seen during the past week in drought affected areas of southern Mozambique and eastern South Africa as a surface cold front pushed through the region. Similar rains are possible in the area during the next 7 days, though long term drought conditions will remain throughout the area. The past season's rainfall deficits continue to yield problems in the area as crop and livestock problems are reported.

8) Heavy rainfall during the last 7 days in southern Liberia have decreased dryness in the area, though seasonal precipitation deficits remain due to a weak past few months. In Cote d'Ivoire, rainfall continues to push southward into central areas of the country and dryness decreases. Rains are generally expected to continue in the region and moisture should increase accordingly.

Timothy B Love