The African Monsoon Recent Evolution and Current Status

1
The African Monsoon Recent Evolution and Current
Status
Update prepared by Climate Prediction Center / NC
EP
21 March 2008
For more information, visit http//www.cpc.ncep.
noaa.gov/products/Global_Monsoons/African_Monsoons
/precip_monitoring.shtml
2
Outline
Highlights Recent Evolution and Current Condit
ions
NCEP GEFS Forecasts Summary
3
Highlights

• Beneficial rains returned to South Africa for the
  second consecutive week, while light or no rain
  persisted over the southern areas of Mozambique
  and Zimbabwe.
• Light or no rain continued to delay the onset of
  the rainy season in many areas in the Greater
  Horn of Africa, including Kenya and Ethiopia.
  

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Overview

• Over the past 7 days, moderate to heavy rains
  sustained moisture surpluses over many areas in
  southern Africa, including South Africa and
  Namibia. Moderate to heavy downpours also
  returned in above average rains over southeastern
  Angola, Zambia, northern Zimbabwe, central
  Mozambique, southern Malawi, western Botswana,
  and western Tanzania. Rainfall was near average
  over southwestern Kenya. However, light to
  moderate rains sustained moisture deficits in
  many areas of the Greater Horn of Africa,
  including most areas in Kenya, much of Ethiopia,
  where the Belg rains are yet to settle, southern
  Somalia, Uganda, Rwanda, and Burundi. Rainfall
  was also below average over the Gulf of Guinea
  region, while seasonably dry weather prevailed in
  the Sahel.
• Over the last 30 days, the impact of TC Ivan and
  Jokwe resulted in above average rainfall
  rainfall along the west coast of Madagascar and
  portions of northern Mozambique. The wet
  conditions over the past week in South Africa
  resulted in above average rainfall for the last
  30 days. Rainfall was also above average over
  portions of western Botswana, and central
  Namibia. However, lighter than average rains
  offset the impact of TCs Ivan and Jokwe and
  sustained moisture deficits along the east coast
  of Madagascar. Lower than average rains also
  sustained moisture deficits over southern
  Mozambique, Zimbabwe, eastern Botswana, most
  areas in Zambia, and portions of central
  Tanzania. Light rains also continued to sustain
  moisture deficits over most areas in Kenya,
  Ethiopia, southern Sudan, and Uganda.
• Over the last 90 days, rainfall was overall above
  average over most areas in southern Africa,
  except for the southern areas of Mozambique and
  Zimbabwe, central Madagascar, northeastern
  Zambia, and northern Angola.
• For the period 22-28 March 2008, the NCEP global
  ensemble forecasts (GEFS) suggests that there is
  a 90 chance or above for precipitation to exceed
  50 mm over most areas in Tanzania, and
  southwestern Kenya, and local areas along the
  Gulf of Guinea coast. There is a 95 chance for
  precipitation to exceed 25 mm over the
  Kwazulu/Natal province of South Africa.
  According to the GEFS, the chance for moderate to
  heavy rains to occur in eastern Africa is weak.

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Rainfall Patterns Last 7 Days
During the past 7 days, rainfall was again above
average over portions of southern Africa,
including northwestern Namibia, southeastern
Angola, Zambia, northern Zimbabwe, central
Mozambique and southern Malawi, the Maize
Triangle of South Africa, western Botswana, and
western Tanzania. Rainfall was also near average
over southwestern Kenya, but was lower than
average over eastern Kenya, Uganda, and Ethiopia,
where the Belg rains are yet to settle.
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Rainfall Patterns Last 30 Days
Over the last 30 days, rainfall was above average
along the west coast of Madagascar and portions
of northern Mozambique as a result of TCs Ivan
and Jokwe. Rainfall was also above average over
portions of northeastern South Africa, western
Botswana, and central Namibia. However, lighter
than average rains sustained moisture deficits
along the east coast of Madagascar, southern
Mozambique, Zimbabwe, eastern Botswana, most
areas in Zambia, and portions of central
Tanzania. Light rains also continued to sustain
moisture deficits over most areas in the Greater
Horn of Africa, central Africa, and the Gulf of
Guinea region.
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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 due in part to
TCs Ivan and Jokwe. Rainfall was also above
average over southern Zambia, central Mozambique,
northern Botswana, and much of Namibia. Overall,
Madagascar, received above average rainfall along
its southwest and northeast coastal areas.
Recent short term dryness sustained moisture
deficits over the southern areas of Zimbabwe and
Mozambique.
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Recent Evolution Rainfall

• Recently, southern Mozambique (top panel)
  received isolated heavy rains over the past 10
  days, but not enough to offset the moisture
  deficits observed over the past several weeks.
  Since TC Jokwe, rainfall has been below average
  over southern Madagascar (middle panel). Crops
  in the Maize Triangle of South Africa benefited
  from heavy rainfall over the past week..

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Atmospheric CirculationLast 7 Days
_at_
AH
AM
Over the past 7 days, low level easterly wind
anomalies (left panel) persisted over the central
Indian Ocean (IO) between 10 and 20S. The St.
Helen and Mascarene high pressure systems
(indicated by AH and AM on the left panel) also
strengthened, creating favorable conditions for
frontal systems to move across southern Africa.
The moderate to heavy rains observed over South
Africa over the last 7 days were also associated
with the upper level atmospheric anomalous
anticyclonic (counter clockwise) circulation
(indicated with the _at_ sign on the right panel).
The dryness over eastern Africa was associated
with low level westerly wind anomalies over the
equatorial IO.
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NCEP GEFS Model ForecastsNon-Bias Corrected
Probability of precipitation exceedance
Week-1Valid Mar 22-28, 2008
The NCEP global ensemble forecast system (GEFS)
suggest that there is a 90 chance or above for
precipitation to exceed 50 mm over most areas in
Tanzania, and southwestern Kenya, and local areas
along the Gulf of Guinea coast line. There is a
95 chance for precipitation to exceed 25 mm over
the Kwazulu/Natal province of South Africa.
According to the GEFS, the chance for moderate to
heavy rains to occur in eastern Africa is weak.
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Summary

• Over the past 7 days, moderate to heavy rains
  sustained moisture surpluses over many areas in
  southern Africa, including South Africa and
  Namibia. Moderate to heavy downpours also
  returned in above average rains over southeastern
  Angola, Zambia, northern Zimbabwe, central
  Mozambique, southern Malawi, western Botswana,
  and western Tanzania. Rainfall was near average
  over southwestern Kenya. However, light to
  moderate rains sustained moisture deficits in
  many areas of the Greater Horn of Africa,
  including most areas in Kenya, much of Ethiopia,
  where the Belg rains are yet to settle, southern
  Somalia, Uganda, Rwanda, and Burundi. Rainfall
  was also below average over the Gulf of Guinea
  region, while seasonably dry weather prevailed in
  the Sahel.
• Over the last 30 days, the impact of TC Ivan and
  Jokwe resulted in above average rainfall
  rainfall along the west coast of Madagascar and
  portions of northern Mozambique. The wet
  conditions over the past week in South Africa
  resulted in above average rainfall for the last
  30 days. Rainfall was also above average over
  portions of western Botswana, and central
  Namibia. However, lighter than average rains
  offset the impact of TCs Ivan and Jokwe and
  sustained moisture deficits along the east coast
  of Madagascar. Lower than average rains also
  sustained moisture deficits over southern
  Mozambique, Zimbabwe, eastern Botswana, most
  areas in Zambia, and portions of central
  Tanzania. Light rains also continued to sustain
  moisture deficits over most areas in Kenya,
  Ethiopia, southern Sudan, and Uganda.
• Over the last 90 days, rainfall was overall above
  average over most areas in southern Africa,
  except for the southern areas of Mozambique and
  Zimbabwe, central Madagascar, northeastern
  Zambia, and northern Angola.
• For the period 22-28 March 2008, the NCEP global
  ensemble forecasts (GEFS) suggests that there is
  a 90 chance or above for precipitation to exceed
  50 mm over most areas in Tanzania, and
  southwestern Kenya, and local areas along the
  Gulf of Guinea coast. There is a 95 chance for
  precipitation to exceed 25 mm over the
  Kwazulu/Natal province of South Africa.
  According to the GEFS, the chance for moderate to
  heavy rains to occur in eastern Africa is weak.