The African Monsoon Recent Evolution and Current Status Include Week-1 and Week-2 Outlooks

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The African Monsoon Recent Evolution and Current
StatusInclude Week-1 and Week-2 Outlooks
Update prepared by Climate Prediction Center /
NCEP 19 December 2011
For more information, visit http//www.cpc.ncep.n
oaa.gov/products/Global_Monsoons/African_Monsoons/
precip_monitoring.shtml
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Outline

• Highlights
• Recent Evolution and Current Conditions
• NCEP GEFS Forecasts
• Summary

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HighlightsLast 7 Days

• Weekly total rainfall exceeded 75mm across
  portions of Zimbabwe, Zambia and Tanzania, while
  southwestern DRC, many parts of Angola and
  northern Namibia had little or no rainfall.
• Week-1 outlooks call for an increased chance for
  above average rainfall over eastern Angola,
  southeastern DRC, western and central Tanzania,
  northern Malawi, eastern South Africa, Lesotho
  and Swaziland.

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Rainfall Patterns Last 7 Days
During the past seven days, below average
rainfall was observed over portions of southern
Cameroon, much of Gabon, Equatorial Guinea, many
parts of Congo, central and southern DRC, many
parts of Angola, northern Namibia, parts of
eastern Zambia, Malawi, northern Mozambique,
Madagascar, southern Kenya and portions of South
Africa. In contrast, moisture surpluses were
observed over parts of northeastern DRC, local
areas in Uganda and Ethiopia, parts of southern
Somalia, much of Tanzania, western and central
Zambia, eastern Angola, northern Botswana,
Zimbabwe and southern Mozambique.
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Rainfall Patterns Last 30 Days
During the past 30 days, parts of Liberia,
southern Ghana, southern Nigeria, southern
Cameroon, Gabon, Equatorial Guinea, much of
Congo, southern CAR, central and northern DRC,
eastern Zambia, Malawi, portions of northern
Zimbabwe, portions of South Africa, Swaziland,
central and northern Madagascar received below
average rainfall. In contrast, above average
rainfall was observed over local areas in central
Congo, portions of southern DRC, many parts of
Angola, western Zambia, northern Namibia,
northern Botswana, western and southern Zimbabwe,
portions of southern Madagascar, much of
Tanzania, Rwanda, Burundi, Uganda, Kenya,
southern Ethiopia and southern Somalia.
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Rainfall Patterns Last 90 Days
During the past 90 days, coastal Cote DIvoire,
portions of southern Ghana, southern Benin,
southern Gabon, central Congo, portions of CAR,
many parts of DRC, Uganda, western and northern
Tanzania, much of Kenya, southern Somalia,
southern Ethiopia, western Zambia, northern
Angola and northern Botswana received above
average rainfall. Below average rainfall was
observed across portions of southern Mauritania,
southern Senegal, southern Mali, central Nigeria,
western Cameroon, northern Gabon, Equatorial
Guinea, local areas in northern Congo, portions
of Sudan and Ethiopia, local areas in Angola,
many parts of South Africa, Madagascar and
portions of Botswana.
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Rainfall Patterns Last 180 Days
During the past 180 days, rainfall was above
average across northern Guinea, central Mali,
Ghana, southern Benin, local areas in Chad,
southern Gabon, parts of Congo, northern CAR,
portions of DRC, southern South Sudan Republic,
Uganda, much of Kenya, Rwanda, Burundi, southern
Ethiopia, central and southern Somalia, northern
and western Tanzania, northern Angola and western
Zambia. Moisture deficits were observed across
southern Mauritania, southern Senegal, coastal
Guinea Conakry, Sierra Leone, Liberia, western
Cote DIvoire, local areas in western Burkina
Faso, western Niger, many parts of Nigeria,
portions of Cameroon, northern Gabon, eastern
Sudan, Eritrea, Ethiopia, portions of South
Africa and Madagascar.
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Recent Rainfall Evolution
Daily evolution of rainfall over the last
90 days at selected stations reflects the recent
decrease in rainfall sustained rainfall
deficits in parts of Angola (bottom panel-left).
In contrast, the recent increase in rainfall over
southern Zimbabwe resulted in moisture surpluses
(bottom panel right). In contrast, many parts
of Tanzania continued to have above average
rainfall (top panel right).
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Atmospheric CirculationLast 7 Days
The 850hPa wind anomaly (left panel) featured
anomalous northwesterlies from the Atlantic Ocean
turning into westerlies and converging across
Zambia and the neighboring areas. Anomalous wind
convergences were also observed across Tanzania
and southern Mozambique, while anticyclonic
anomaly prevailed over Mozambique Channel. The
200hPa wind anomaly (right panel) featured
anomalous anticyclonic flow across southeastern
Africa.
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NCEP GEFS Model ForecastsNon-Bias Corrected
Probability of precipitation exceedance Week-1
Valid 20 26 December 2011Week-2 Valid 27
December 2011 02 January 2012
For week-1 (left panel), there is an increased
chance for rainfall to exceed 50 mm over parts of
Angola, southern DRC, Zambia Tanzania and parts
of South Africa. For week 2 (right panel), the
probabilities of exceedence 50mm tend to decrease
across many of these areas.
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Experimental Week-1 Precipitation Outlooks
Week-1 Outlook 20 26 December 2011

• There is an increased chance for above average
  rainfall over eastern Angola, southeastern DRC,
  western and central Tanzania, and northern
  Malawi Westerly anomalies from the Atlantic
  Ocean and stronger than normal convergence across
  the Congo Air Boundary (CAB) area are expected to
  enhance rainfall in the region. Confidence
  Moderate
• There is an increased chance for above average
  rainfall over eastern South Africa, Lesotho and
  Swaziland Interactions between mid-latitude and
  tropical systems across southeastern Africa are
  expected to enhance rainfall in the region.
  Confidence Moderate

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Experimental Week-2 Precipitation Outlooks
Week-2 Outlook 27 December 2011 02 January 2012
No forecast
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Summary

• During the past seven days, below average
  rainfall was observed over portions of southern
  Cameroon, much of Gabon, Equatorial Guinea, many
  parts of Congo, central and southern DRC, many
  parts of Angola, northern Namibia, parts of
  eastern Zambia, Malawi, northern Mozambique,
  Madagascar, southern Kenya and portions of South
  Africa. In contrast, moisture surpluses were
  observed over parts of northeastern DRC, local
  areas in Uganda and Ethiopia, parts of southern
  Somalia, much of Tanzania, western and central
  Zambia, eastern Angola, northern Botswana,
  Zimbabwe and southern Mozambique.
• During the past 30 days, parts of Liberia,
  southern Ghana, southern Nigeria, southern
  Cameroon, Gabon, Equatorial Guinea, much of
  Congo, southern CAR, central and northern DRC,
  eastern Zambia, Malawi, portions of northern
  Zimbabwe, portions of South Africa, Swaziland,
  central and northern Madagascar received below
  average rainfall. In contrast, above average
  rainfall was observed over local areas in central
  Congo, portions of southern DRC, many parts of
  Angola, western Zambia, northern Namibia,
  northern Botswana, western and southern Zimbabwe,
  portions of southern Madagascar, much of
  Tanzania, Rwanda, Burundi, Uganda, Kenya,
  southern Ethiopia and southern Somalia.
• During the past 90 days, coastal Cote DIvoire,
  portions of southern Ghana, southern Benin,
  southern Gabon, central Congo, portions of CAR,
  many parts of DRC, Uganda, western and northern
  Tanzania, much of Kenya, southern Somalia,
  southern Ethiopia, western Zambia, northern
  Angola and northern Botswana received above
  average rainfall. Below average rainfall was
  observed across portions of southern Mauritania,
  southern Senegal, southern Mali, central Nigeria,
  western Cameroon, northern Gabon, Equatorial
  Guinea, local areas in northern Congo, portions
  of Sudan and Ethiopia, local areas in Angola,
  many parts of South Africa, Madagascar and
  portions of Botswana.
• Week-1 outlooks call for an increased chance for
  above average rainfall over eastern Angola,
  southeastern DRC, western and central Tanzania,
  northern Malawi, eastern South Africa, Lesotho
  and Swaziland.