Weekly Introduction:
Update of El Niño:
Synopsis: Weak warm-episode (El Niño) conditions are expected to continue for the next three months.
Positive sea surface temperature (SST) anomalies greater than +0.5°C (~1°F) persisted across most of the central and western equatorial Pacific during December 2004. The patterns of anomalous warmth in the equatorial Pacific in recent months indicate that a weak warm episode has developed. However, through December there has been a lack of persistent enhanced convection over the anomalously warm waters of the central equatorial Pacific, which has limited El Niño-related impacts on the global pattern of precipitation.
Based on the recent evolution of oceanic and atmospheric conditions and on a majority of the statistical and coupled model forecasts, it seems most likely that weak warm episode (El Niño) conditions will persist for at least the next three months. However, there is considerable uncertainty concerning future developments in the extreme eastern equatorial Pacific (the classical El Niño region). This discussion is a consolidated effort of NOAA and its funded institutions.
The actual forecasts for the regions in Africa will be updated next week.
Locust Update:
The report from the Food and Agriculture Organization (FAO) of the United Nations on the locust situation in western Africa was last updated on January 10 (http://www.fao.org/NEWS/GLOBAL/locusts/Locuhome.htm). Some immature Desert Locust swarms persist in parts of Gambia, in southern Senegal, in northern, central and eastern Guinea Bissau, and probably small populations are present in neighboring areas of northern Guinea.
Additional details can be found at the USAID web site for Assistance for Emergency Locust/Grasshopper Abatement (AELGA) at http://www.aelga.net and the AGRHYMET site at http://www.agrhymet.ne.
Weather Hazards Assessment Graphic:
Weather Hazards Text Explanation:
1. Rainfall during both the long and short rainy seasons of 2004 was well below normal across portions of Ethiopia's Somali region, adjacent parts of Somalia, as well as portions of southern Kenya and northeastern Tanzania. The dry conditions have reduced moisture for pastures in pastoral areas and crops in the bi-modal growing areas. Conditions are expected to be dry during the period. Although showers occasionally occur during January and February over southern Kenya, the next chance for significant seasonal rains will come in March. In eastern Ethiopia, the next chance for significant seasonal rains will come in April with the onset of the long rains.
2. Rainfall during 2004 was about 50 percent of average across western portions of Ethiopia's Afar region and adjacent parts of the Tigray and Amhara regions. This has resulted in degraded pastures and water supply problems in and around the area. There is a chance for some isolated showers during the period, however conditions are expected to remain dry over most areas. The next opportunity for relief will come in late February and March with the onset of the Belg rains. The best chances for significant improvement will come in July and August, which tend to be the wettest months of the year.
3. Hot, dry Sahara winds caused the seasonal rains to end early this year across much of central and northern Darfur in Sudan, as well as adjacent parts of Chad. This has resulted in a reduction of the already meager forage for grazing and scarce drinking water supplies. The impact of the poor grazing conditions and low water supplies will be exacerbated by the ongoing crisis in the region. Conditions will remain seasonably dry until the onset of seasonal rains in late June or July. Therefore, no improvement is expected for several months.
4. Rainfall over the past three months has been lighter than normal over portions of southern Uganda and northwestern Tanzania, with totals ranging from 50 to 70 percent of the long term average. These lighter than normal rains have likely stressed second season crops and may result in yield reductions. Second season crop harvesting usually occurs in this area during January. There is a chance for showers during the period which may hamper harvesting efforts.
5. Long term dryness over Lake Victoria has resulted in very low lake levels. Although recent rains have resulted in a modest rise in the lake's level, Lake Victoria remains near its lowest level in 10+ years. As the source of the Nile, Lake Victoria plays an important role in ensuring household food security in southern Sudan by promoting seasonal flooding along the Nile, which is crucial for fish and wild plants (water lily) production and pasture replenishment during the dry season (November to May). This flooding has been well below normal this year. For more information on the food security effects of this anomaly, please visit the southern Sudan country site at www.fews.net/sudan. Showers are expected over and around Lake Victoria during the period, however little change in Lake Victoria's level is anticipated. Rainfall over Lake Victoria tends to be light during January and February. Heavier rains typically fall during March and April, with April being the wettest month of the year.
6. Persistent heavy rainfall during late November and most of December soaked western Madagascar, northern Mozambique, the northern two thirds of Malawi and eastern Zambia. During December, 250-500+ mm of rain had fallen over the region, which is more than twice the normal amount. These persistent heavy rains have resulted in saturated soils, swollen rivers and flooding across parts of the area. The rain continued into early January, albeit lighter than previous weeks. Widespread showers and thunderstorms are expected throughout the period. The additional rainfall may result in flooding problems in and around the region. Downstream along the Shire River in southern Malawi, levels are high. The Shire River is the main tributary of the lower Zambezi. The elevated levels on the Shire have resulted in higher levels along the Zambezi. At Marromeu in Mozambique, the river level was 4.45 meters on January 10th according to the Agencia de Informacao de Mozambique. Flood alert level is 4.75 meters. With the additional rains in the Shire River Basin, the potential exists for flooding in prone areas along the Shire and lower Zambezi Rivers in Malawi and Mozambique. However, major flooding is not expected.
7. After a dry December, recent rains favored crops and pastures while easing dryness across north-central Namibia and south-central Angola. However, moisture in some areas remains below normal. Showers and thunderstorms are expected to continue through the period across most of northern Namibia and southern Angola. Therefore, further improvement is expected as moisture deficits are reduced or eliminated.
8. A 3 to 5 week dry spell continues across much of southern Mozambique, eastern Swaziland, southern Zimbabwe, as well as adjacent parts of Botswana and South Africa. Many areas have gone 30+ days with little, if any measurable rainfall with rainfall totals since November 1 running 45 to 70 percent of normal. Furthermore, temperatures have been hot across the area. The dry, hot conditions have stressed crops and pastures and are beginning to reduce river flows. According to the Agencia de Informacao de Mozambique, the Limpopo, measured at the town of Chokwe, fell from 0.57 meters on January 6th to 0.41 meters on January 10th. The low water levels threaten the running of the Chokwe irrigation scheme, which is the largest in Mozambique. Low levels are also being reported on the Save River. The good news is that rain is expected across the region, beginning January 16th. The rainfall may be substantial and is expected to boost moisture for crops and pastures while raising river levels across the region.
9. Despite near normal rainfall near the coastal areas, interior Western Cape in South Africa received only 25 to 60 percent of the normal rainfall from April-September of 2004, normally the wettest time of year. The lack of rain during the wet season has resulted in severe water shortages, stressed pastures and much below normal soil moisture levels across interior parts of the province during the dry season. Some dams are at or near record low levels. Conditions are expected to remain dry during the period. The earliest opportunity for improvement will come in March-April when rainfall amounts typically begin to pick up.
10. Atmospheric circulation patterns over the North Atlantic have resulted in a two month dry spell across western Morocco. Rainfall amounts have been about half of normal since November 1, reducing moisture availability to winter grains. However, temperatures have been cooler than normal, which has reduced moisture demand and crop development. Although there is the possibility of showers along the coast late in the period, no soaking rains are expected.
AUTHOR: Chester V Schmitt