Africa: Drought and Floods Hazards Assessment: 19 Jun 2003
EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION
Oceanic and atmospheric conditions in the tropical Pacific during May were consistent with a developing cold episode. Negative sea-surface temperature anomalies strengthened across the central and eastern equatorial Pacific during May, as significant decreases in SST anomalies occurred in all of the Niño regions. By early June equatorial SSTs were near or below normal between 165?W and the South American coast, with only a small area of residual positive SST anomalies west of the date line between 155?E and 175?E. The observations in oceanic and atmospheric variables indicate that a transition to La Niña is underway and that La Nina conditions are likely to develop over the next few months.
Most statistical and coupled model forecasts indicate that either near-neutral or La Niña conditions will occur during the last half of 2003. However, current conditions and recent trends favor the development of cold episode (La Niña) conditions in the tropical Pacific during the next few months.
This discussion is a consolidated effort of NOAA and its funded institutions.
Over Africa, conditions were slightly wetter than normal across parts of central and southern Mozambique, northeastern South Africa, and Zimbabwe during last week as a cold front pushed through the area, bringing up to 60 mm of rainfall on June 10th. Otherwise, conditions remained dry in southern Africa. In eastern Africa, locally heavy thunderstorms yielded weekly rainfall totals greater than 50 mm in parts of northern coastal Kenya and southern coastal Somalia, though dryness continued elsewhere in Somalia and throughout Tanzania. Daily thunderstorms were seen in much of the western Ethiopia Highlands, as seven day rainfall accumulations topped 150 mm locally, however eastern areas remained dry. Moderate rainfall continued as well in southwestern Kenya, though flooding is no longer a serious threat. Further west, rainfall was heavy throughout most of Nigeria, and scattered intense thunderstorms brought locally heavy precipitation to southern Senegal, southern Mali, and Gulf of Guinea countries. Rains were lighter than normal though in most of Gabon, southern Cameroon, and southern Congo. Rainfall, especially on June 11 and 14, helped much of northern Morocco accumulate weekly totals exceeding 30 mm.
WEEKLY AFRICAN WEATHER HAZARDS ASSESSMENT STATEMENT
JUNE 18, 2003 DISCUSSION:
1) A severe drought last season has resulted in poor pasture conditions and moisture deficits across much of northern Senegal, southern Mauritania and adjacent portions of Mali. Significant improvement is not expected until at least July, with the onset of the wet season.
2) Poor performing belg rains may negatively impact long season crops near the towns of Desee and Weldiya in northern Ethiopia. Conditions are expected to remain mostly dry throughout the week. Significant rains are expected with the onset of the Meher season in early July.
3) Main season rains have been slow to start around and just east of Lake Tana in the Ethiopian Highlands. This may have some impact on local agriculture as rain should be falling during early June. However, substantial seasonal rains across this region typically set in during late June or the beginning of July. Therefore, no major problems are anticipated in the near term. The potential for significant negative impacts to local agriculture will increase if the dry trend continues for several weeks.
4) Rainfall totals for the March through May wet season (long rains) were between 20% and 40% of normal across portions of northeastern Tanzania and adjacent southeastern Kenya. These rainfall deficits may have a substantial negative impact on local crops dependant on these rains. This area is expected to remain seasonably dry until October with the onset of the next wet season, which is more significant for local agriculture.
5) Rainfall totals during the 2002-2003 wet season were less than half of normal across much of Swaziland, northeastern South Africa and the southern most provinces of Mozambique. This includes significant portions of the Limpopo River Valley. Precipitation deficits of 150 to 400 mm have raised concerns over water shortages across the region. Seasonably dry conditions are expected during the period.
AUTHOR: Chester V. Schmitt