Africa: Drought and floods hazards assessment 23 Dec 2003

from US Agency for International Development
Published on 23 Dec 2003

Africa Weather Hazards Assessment Text Explanation December 25-31, 2003

1) Multi-seasonal drought continues to affect parts of the Sool Plateau region of northern Somalia. Dryness has been observed during the past two weeks, and little precipitation is expected until March.

2) The rainy season has ended in much of the GHA, and hydrological deficits continue to exist in parts of south central Ethiopia and north central Kenya as well as in west central Somalia and southeastern Ethiopia. Though some surrounding areas have experienced precipitation deficits during the recent October-November short season, cumulative hydrological problems from the past two seasons are more centralized. Little relief is expected until precipitation normally increases in March.

3) Healthy rains have fallen throughout most of central and western Tanzania during the past two weeks, alleviating dryness in the region. While spotty showers and thunderstorms have moved over eastern Tanzania, near normal month-to-date rainfall has not moderated November rains which were less than 15 percent of normal. In central Kenya, rainfall since October is around 10-50 percent of normal, with seasonal deficits approaching 300 mm locally. With central Kenya rains normally ending in mid-December, the area will need to be evaluated for off-season hydrological dryness within the next couple of weeks. Generally dry conditions can be expected within both regions next week.

4) Short term dryness has been evident since mid-October throughout much of central and southern Mozambique as well as most of eastern South Africa. Though abnormal October rainfall in northern Gaza and Inhambane provinces in Mozambique has increased moisture in the area, much of Tete, Manica, Sofala, and Maputo provinces suffer from November-to-present deficits of 150-200+ mm. While eastern provinces of South Africa are faring slightly better, 2-month rains are running from 20-50 percent of normal locally, with recently observed higher than normal temperatures. A frontal system currently producing rainfall over the Maize Triangle region should linger in the area and drift to the north into central Mozambique during the week, producing beneficial rainfall throughout the region.

5) Little has changed in and around Lesotho during the past week with respect to seasonal rainfall deficits. Frontal rains will likely miss the area and dryness should continue through the end of the year.

6) See #4 for current seasonal information. Long-term precipitation deficits also exist throughout parts of southern Mozambique and eastern South Africa, including Zimbabwe, due to poor performing rainfall during the 2002-03 long season. As noted in #4, recent thunderstorms have produced beneficial rains during the past two days and additional relief is possible during the week.

Timothy Love

Tropical Cyclone Cela

The major element this past week was the impact of Tropical Cyclone Cela. We initiated coverage of Cela on December 4 when it was in the western portion of the South Indian Ocean. In figure we depict the track of the storm through December 22 along with the accumulated rainfall for the period December 8-21. We see that Cela took a westerly course, initially, and made landfall on the northern portion of Madagascar and weakened. It then entered the Mozambique Channel where the warm sea surface temperature helped regenerate it to Tropical Storm and Cyclone strength. Fortunately, its path took a southward turn down the Mozambique Channel and it did not make landfall again. The storm did, however, have a major impact on the rainfall in Madagascar and northern Mozambique. As indicated in the figure, west central portions of Madagascar received over 300mm of rain from the cyclone whereas northern Mozambique and most of Madagascar received about 75-150 mm. The area just south of the landfall site in northeastern Madagascar received over 200 mm.

Elsewhere over Africa, the heaviest rainfall continued to occur over the south-central portion of the continent extending from Gabon and Angola in the west through the DRC and into Uganda on the east . No rainfall was observed in Somalia with only light rainfall in soutwestern Ethiopia and southwestern Kenya. Heavy rainfall was also observed in Tanzania, Malawi, Zambia and Angola. Only light rainfall was observed in southern Africa with locally scattered heavy showers in Botswana, Zimbabwe and northern South Africa.

Northern Africa indicated relief from the heavy rainfall of recent weeks with only light rainfall observed.

Cyclone Cela (03S) Cumulative Track
December 4-22, 2003 Cyclone Path
December 8-21, 2003 Accumulated Rainfall