Africa: Drought and floods hazards assessment: 30 Oct 2003

Report
from US Agency for International Development
Published on 30 Oct 2003


Update of the ITCZ Position
For the period of October 11-20, 2003, the Intertropical Convergence Zone over Africa was located near 14.2 degrees north latitude, or around 0.3 degrees north of the 1988-2002 normal for the dekad. The rate of southward descent somewhat increased for this period as the ITCZ moved around 1.0 degree over the past 10 days. In the Sahel, the ITCZ has shown the most southward movement, as during the last period the northern extent was almost 17 degrees north, while during the second dekad it moved to around 15 degrees north or a 2 degree southward movement. The 10-day rainfall totals seem to correlate with this sharp movement as the heaviest rains are now confined to the immediate coastal areas of the Sahel region. Liberia, Cote d'Ivoire, and southern portions of Ghana picked up as much as 200 mm locally. Other isolated showers were further north in Guinea and southern Senegal, but rainfall totals only reached 50 mm. Through central and eastern portions of Africa the ITCZ remained slightly north (central areas) or near climatology (eastern). Most of the widespread rain showers were confined to southern Chad where amounts were up to 75 mm and in southern Sudan, where isolated amounts reached greater than 100 mm.

African Hazards Prologue

Locally heavy minor season rains hit southern Somalia and central and eastern Kenya during October 21-27, improving moisture conditions, but abnormally dry weather remained over southeastern Ethiopia and central and northern Somalia, where the season has yet to start. Up to 110 mm fell on the Kenyan coast on October 28, while 82 mm fell in central Kenya. Despite some recent scattered showers, more rain is needed in northern coastal Tanzania, where significant rainfall deficits date back to the main rainy season early in the year. To the south, heavy rains in Zimbabwe and southern Mozambique continued to relieve long-term drought. Weekly rainfall ranged from 30 to 75 mm over central and southeastern Zimbabwe, as well as several parts of southern Mozambique. In contrast, below-normal rains fell over southeastern and eastern South Africa, as well as Lesotho and Swaziland. Amounts in this region, which has seen persistently below-normal rains since September, ranged from 1 to 10 mm. In West Africa, unusually heavy rains fell over northern and western Mauritania, Spanish Sahara, and the arid areas of western Algeria and southern Morocco, with some locations reporting as much as 50 mm in a single day (October 21).




AFRICA WEATHER HAZARDS ASSESSMENT TEXT EXPLANATION OCTOBER 30 - NOVEMBER 5, 2003

1) Virtually no rainfall occurred over drought affected areas in and surrounding the Sool Plateau in northern Somalia during the month of October 2003. This area should normally receive rains from 10-50 mm over the course of October and little to no precipitation in November. For the season thusfar, the region has received 0-25 percent of normal precipitation and long term drought will continue through the dry season. Climatology states that the next season should begin sometime around late March.

2) 7-Day precipitation totals in much of southern Ethiopia ranged from 10-30 mm from October 21-27, though areas to the east remained unseasonably dry. The hazard region depicted here consists of two areas. The darker shaded region to the west represents long term dryness due to poor performing rains from June-October 2003 while the eastern area symbolizes shorter term dryness arising from a lack of rainfall from late September to the present. The western region should continue to see some relief during the next week, though this moisture will not likely reach eastern problematic areas. The fact that rainfall normally begins to decrease in southeastern Ethiopia in early November does not bode well for dry season moisture conditions in the area.

3) Seasonal rainfall deficits continue to threaten food security conditions from southern coastal Kenya to northern coastal Tanzania. Rainfall from August thru mid October has been much lighter than normal, with some areas in the region seeing virtually no precipitation whatsoever during the period. This seasonal dryness compounds the effects of moderate to severe drought during the MAM season of 2003. Meteorological conditions are becoming favorable for precipitation in the region, though as of recent, most rainfall has been confined to north of the area. November rains will be critical in providing moisture for crops and livestock, as between 100-150 mm should normally fall throughout the month.

4) Moderate rainfall amounts were seen in parts of the northern Limpopo Basin in southern Mozambique and South Africa during the last week, with accumulations reaching 75 mm in the hazard area depicted. The rains that have fallen in October were mainly confined to the outskirts of the area experiencing long term drought due to much below normal rains during the 2002-03 long season. Up to 50 mm of precipitation is expected in the area during the next week, though widespread rainfall totals will be generally around 10-25 mm.

5) The region in and surrounding Lesotho in southern Africa experienced a much drier than normal winter rainfall season and conditions have not improved substantially during the month of October. The area continues to receive less than normal precipitation though slightly lower than normal temperatures should not be considerably affecting the region. Generally light showers are likely during the next week though rainfall may be of the hit-and-miss variety.

6) Though September 2003 rainfall amounts were near normal along coastal Natal State in South Africa, October deficits are running from 50-100 mm below normal. This translates to month to date rains of between 20-50 percent of normal and thus dryness concerns exist. Light showers are possible during the next week, with 7-day accumulations between 10-30 mm.

Timothy Love