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Global Weather Hazards Summary: July 27 - August 2, 2018

Situation Report
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Heavy rainfall triggers flooding in the Sahel

  1. Since mid-July, torrential rains received in western Nigeria have triggered floods, damages to infrastructure and fatalities in the Ogun and Katsina states of the country.

  2. Locally torrential rainfall forecast over parts of western Sudan and eastern Chad may trigger flooding next week.

  3. Irregular rainfall since June has resulted in significant moisture deficits and deteriorated ground conditions across parts of western Uganda, northeastern DRC, and southern South Sudan.

Africa Overview

Rainfall recorded over Senegal, Guinea, and Sierra Leone

Last week, heavy rainfall was recorded over several Gulf of Guinea countries. The highest weekly accumulations (>100 mm) were registered over the parts of southern Senegal, Guinea, southern Mali and Sierra Leone (Figure 1), with flooding reported in Liberia. Heavy rainfall was also received in parts of Nigeria following flood events that affected the Ogun and Katsina states of the country. Light rainfall also received across much of the Sahel.

Although locally heavy rains across the Gulf of Guinea countries have triggered flooding, overall it is expected to benefit cropping and pastoral areas of West Africa. In Senegal and Sierra Leone, the return of heavy rains has helped to mitigate moisture deficits. However, at least two consecutive weeks of below-average rainfall has led to marginally below average conditions over northeastern Nigeria (Figure 2).

Next week, average to above-average rainfall is expected throughout much of West Africa. The highest weekly totals (>75 mm) are forecast for parts of Guinea, western Mali, eastern Burkina Faso and in parts of Nigeria. There is some potential for decreased rainfall amounts over parts of southern Mauritania and northern Senegal.

Dryness continues in Ethiopia, South Sudan, Uganda, and DRC

Another week of heavy rainfall (>100 mm) was received across the North Kurdufan, White Nile and Kassala provinces, and in parts of western Ethiopia (Figure 1). The continuation of moderate to locally heavy rainfall over saturated areas may trigger flooding.

As portions of eastern Sudan and western Ethiopia have continued to experience above-average rainfall, there are several areas in Ethiopia that remain dry. In the northern portion of the SNNP region, central Oromia, and eastern Amhara and Tigray region, moisture deficits have strengthened over the past couple of weeks. In the SNNP, much of the dryness has been associated with a prolonged dry spell and a decreased frequency of seasonal rains during July, resulting in less than 25% of their normal rainfall accumulation since late June (Figure 2). Further south, moisture deficits of similar magnitude have also developed across parts of western Uganda, northeastern DRC, and southern South Sudan.

Next week, average to above-average rainfall is expected over western Ethiopia.