Africa Weather Hazards Assessment Text Explanation
April 22-28, 2004
1) Continued dryness relief occurred last week throughout much of the Togdheer and southern Sool Provinces of northern Somalia, while lighter showers increased moisture within the Sanaag province region. Heavy rainfall, with weekly accumulations exceeding 100 mm were seen in the southern Togdheer and western Sool Provinces, and widespread accumulations exceeding 25-50 mm were noted elsewhere. This has greatly improved pasture conditions in the western hazard region, though the effects of 5+ seasons of drought continues to dominate areas to the east. Light showers should fall in the area during the first part of the forecast period and dryness will likely prevail during the latter half.
2) Beneficial rains fell once again in parts of eastern Ethiopia and western Somalia which have experienced dryness since the beginning of 2003. During the past week, widespread accumulations exceeding 50 mm were noted in the southern parts of Harerge and Bale Provinces in Ethiopia and in northern areas of Bakool and Hiraan Provinces in Somalia. While long term hydrological deficits remain due to poor 2003 rainfall, the past three weeks of precipitation have greatly improved conditions in the region. Rains are again probable during the next week.
3) Very heavy rains, exceeding 125 mm locally, fell in parts of the Shebelle River Basin of southern Somalia on April 19th. These rains were followed up by additional moderate to heavy precipitation on the 20th, and latest meteorological forecasts indicate more rains during the next week. As a result, local areas of flash flooding may occur until water levels decrease to normal.
4) Coincident with area 4, rainfall decreased to near- to below-normal levels along much of the Kenya / Tanzania border during the past week. Runoff continues to be problematic, however, near Lake Victoria, as moderate precipitation continued. Up to 75 mm locally, likely sustained any local flooding in the region, as similar accumulations can be expected within the next week.
5) Fortunately, heavy rainfall was not seen during the past week along much of the eastern Kenya / Tanzania border region, so flooding should not be an issue. Unfortunately, virtually no rainfall was recorded in the region, and thus no further improvement of the multi-seasonal dryness was seen. 2-Year precipitation deficits continue to be in the hundreds of millimeters and accumulations are running from 30-70 percent of normal. Light showers may bring additional relief during the next week, as the majority of maize plantings should be completed.
6) 3-Plus weeks of heavy rainfall, with weekly accumulations ranging from 100-250 mm, have drenched parts of coastal Tanzania. Large-scale flooding is less of an issue, though some local problems can be expected with the heaviest of daily rains. Medium range forecasts indicate continued chances of strong storms in the area hilited.
7) With the widespread agricultural problems due to erratic and late to start 2003-04 seasonal rainfall somewhat in the past, continued erratic but regionally beneficial rains were again seen during the past week. Though any crops planted on schedule in much of southeastern Zimbabwe and southern Mozambique may have failed due to poor early rainfall, some later plantings are reaping the benefits of increased moisture. Other late-planted crops nearing the harvesting stage, however, will be adversely affected by the rainfall. Again, light showers are expected during the next week.
8) Virtually no rainfall was recorded during the past week in southern and eastern Angola, Namibia, Zimbabwe, and western Zambia, as river levels of the Upper Zambezi and Kafue decrease. While little rainfall is expected during the forecast period, reports of maintained flooding in and around the Caprivi Strip region in northeastern Namibia warrant the continuation of the hazard area.
Timothy Love
April 22, 2004 Preamble
Update of ITCZ
April 1-10, 2004 marks the first ITCZ analysis of the year. During the current 2004 period, the longitude-averaged position of the ITCZ was near 10.6 degrees north, compared with the 16 year mean of 10.3 north. This overall mean vs current position, with associated dekadal estimated precipitation, is seen in the attached diagram, itcz.jpg. From this image, it can be noted that healthy rainfall occurred in eastern areas of the continent, including much of Ethiopia, western Somalia, Kenya, Uganda, southern Sudan and northern Mozambique. In addition, heavy rainfall was also observed in the central areas, and in the southern portions of western Africa. Examining regions individually, the ITCZ from 10W-10E averaged near 11.7 degrees north, very close to the mean position for the period. Note that the observed southward dip near extreme western areas does not figure into the regional calculation. In the east from 20-35E, a northward push of winds during the current dekad helped to move the ITCZ to the north of its long term mean. The current position is near 9.7N, while the long term mean is closer to 8.7 degrees north. This product will be updated 3 times monthly through the end of the year and can be tracked at the following website.
http://www.cpc.ncep.noaa.gov/products/fews/ITCZ/itcz.html
Locust Infestation
Finally, according to the Food and Agriculture Organization (FAO) of the United Nations, Rome, Italy, http://www.fao.org/NEWS/GLOBAL/locusts/Locuhome.htm) locust swarms have arrived and are laying eggs in the spring breeding areas south of the Atlas Mountains in Morocco and Algeria. Hatching has started in the Draa Valley in Morocco. In the coming weeks, more hatching and band formation will occur there and in Algeria. This will be supplemented by additional swarms from northern Mauritania and the Western Sahara where hopper bands and swarms continue to form. In Niger, hatching and band formation may be in progress in the southern Air Mountains where egg-laying occurred last month. Hatching and band formation is expected in the coming weeks in northern Sudan and southern Egypt where swarms arrived and laid eggs last month. Control operations are in progress in all affected countries, but severe shortages of resources continue to limit their effectiveness in reducing the number of swarms that move towards the spring breeding areas. There are signs that the situation is moving towards the early stages of an upsurge.
NOAA Climate Prediction Center USGS