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Review of recent African monsoon patterns, including NCEP GEFS forecasts and rainfall trends over 90, 30, and 7 days. Detailed analysis of moisture deficits, rainfall patterns, and cyclone impacts in different regions of southern Africa.
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The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 7 March 2008 For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/African_Monsoons/precip_monitoring.shtml
Outline • Overview • Recent Evolution and Current Conditions • NCEP GEFS Forecasts • Summary
Overview • Season-to-date rainfall has been near or above average over many areas in continental southern Africa. However, over the last 30 days, recent dry spells resulted in drier than average conditions over many areas in the region, except for northern and southern Madagascar, northeastern Mozambique, southern Tanzania, and central Namibia. • Over the past week, most areas in southern Africa registered below average rainfall. The dry spell sustained moisture deficits in portions of northeastern South Africa and eastern Botswana, Zimbabwe, and central Mozambique. • For the period 8-14 March 2008, the NCEP global ensemble forecasts (GEFS) shows 70 to over 90% chance for rainfall to exceed 75 mm over southern Angola and portions of the northern coast of Mozambique.
Rainfall Patterns: Last 90 Days Over the past 90 days, rainfall was above average over portions of southern Africa. The largest rainfall departures occurred over southern Angola and northern Mozambique. Rainfall was also above average over southern Zambia, central Mozambique, and northern Botswana. Recent rains helped erase moisture deficits observed earlier in southwestern Madagascar. Rainfall remained below average along the southeast coast of Madagascar, and recent short term dryness contributed to below average rainfall over southern Zimbabwe and portions of northeastern South Africa.
Rainfall Patterns: Last 30 Days Over the last 30 days, a recent dry spell resulted in moisture deficits in the areas including Angola, Zambia, Zimbabwe, most areas in Botswana and Mozambique, and northeastern South Africa. In contrast, moderate to heavy rains resulted in moisture surpluses over central Namibia, and southern Tanzania. Tropical Cyclone Ivan made landfall in Madagascar and contributed to above average rainfall in this region including northern Mozambique.
Rainfall Patterns: Last 7 Days During the past 7 days, light rains resulted in below average rainfall across most areas in southern Africa. The exceptions were local areas along the northeast coast of Madagascar, sectors along the northern coast of Mozambique, and locally over western Botswana.
Recent Evolution: Rainfall Recently, light rains resulted in below average rainfall over central Mozambique, Zimbabwe, and eastern Botswana (top panel). Below average rainfall returned to eastern Madagascar (middle panel) after the period of wetness associated with Tropical cyclone Ivan. The dry spell of the past week sustained moisture deficits over portions of eastern South Africa.
Atmospheric Circulation:Last 7 Days The light rains of the last 7 days in southern Africa were associated with a weakening of the St Helena High pressure system (SH) and a northward shift of the Mascarene High (MH) (left panel). Low level moisture convergence was nearly absent south of 10S. The suppressed rainfall was also associated with upper level easterly wind anomalies (right panel) across the continent south of 15S.
NCEP GEFS Model ForecastsNon-Bias Corrected Probability of precipitation exceedance – Week-1Valid Mar 8-14, 2008 The NCEP global ensemble forecast system (GEFS) suggest a 90% chance or above for precipitation to exceed 75 mm over southern Angola. There is 70 to 90% chance for rainfall to exceed 75 mm along portions of the Mozambique central coast as a result of Tropical Cyclone Jokwe.
Summary • Season-to-date rainfall has been near or above average over many areas in continental southern Africa. However, over the last 30 days, recent dry spells resulted in drier than average conditions over many areas in the region, except for northern and southern Madagascar, northeastern Mozambique, southern Tanzania, and central Namibia. • Over the past week, most areas in southern Africa registered below average rainfall. The dry spell sustained moisture deficits in portions of northeastern South Africa and eastern Botswana, Zimbabwe, and central Mozambique. • For the period 8-14 March 2008, the NCEP global ensemble forecasts (GEFS) shows 70 to over 90% chance for rainfall to exceed 75 mm over southern Angola and portions of the northern coast of Mozambique.
