The Famine Early Warning Systems Network (FEWSNET) says the abnormally high temperatures experienced over Southern Africa since mid-December have increased evapotranspiration*, increasing the surface area experiencing moisture stress.
In its latest Weather Hazards Bulletin for the period 19 January to 28 January, FEWSNET said the combination of intense heat and poor rainfall has worsened ground moisture conditions.
“Although a slight increase in rainfall was recorded in portions of South Africa and central Mozambique compared to the previous week, light rainfall totals of plus or minus 25 mm were widespread in the dry regions of Namibia, Botswana, Zimbabwe, southern Zambia, and western Madagascar last week.
“An analysis of percent of normal rainfall anomalies indicate positive anomalies developing over Tanzania, northern Malawi and northern Mozambique, as well as significant negative anomalies developing much of Zambia, western Mozambique, the Zambezi region in Namibia, Botswana, Zimbabwe and South Africa since mid-December,” FEWSNET said.
The assessment noted that this negative rainfall trend is likely to worsen, with no significant rains until the end of January being a strong possibility. The organisation said the mid-season dry spell is impacting negatively on the longer term seasonal moisture conditions. Halfway into the 2017/’18 farming season, Southern Africa has received below-average rains.
“Although there remains time for moisture recovery due to the length of the monsoon, continuation of below average rainfall in January is likely. Next week, models suggest little relief for southern Africa, with above average temperatures and below average rainfall forecast,” FEWSNET said.
*Evapotranspiration is the sum of evaporation and plant transpiration from the Earth’s land and ocean surface to the atmosphere. (Wikipedia)