The African Monsoon Recent Evolution and Current Status

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The African Monsoon Recent Evolution and Current
Status
Update prepared by Climate Prediction Center / NC
EP
27 October 2008
For more information, visit http//www.cpc.ncep.
noaa.gov/products/Global_Monsoons/African_Monsoons
/precip_monitoring.shtml
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Outline

• Highlights
• Recent Evolution and Current Conditions
• NCEP GEFS Forecasts
• Experimental Week-1 and Week-2 Outlooks
• Summary

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HighlightsLast 7 Days

• During the past 7 days, moderate to heavy rains
  soaked parts of the Greater Horn of Africa,
  including western Kenya, Uganda, southern Sudan,
  and northwestern Tanzania.
• Rainfall continued to linger over pockets in the
  Sahel, while parts of the eastern sector of the
  Gulf of Guinea region received less than average
  rainfall.

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Rainfall Patterns Last 180 Days
Over the past 180 days, rainfall was above
average over most areas in West Africa and
central Africa. In the east, rainfall was below
average in central Sudan , and in pockets over
southwestern Kenya and southern Somalia.
Rainfall was above average over western Ethiopia.
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Rainfall Patterns Last 90 Days
Over the past 90 days, rainfall was above average
over most areas in the western part of the Sahel
and most areas in the Gulf of Guinea region and
parts of central Africa. Rainfall was below
average central Sudan, and above average in the
south and in western Ethiopia.
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Rainfall Patterns Last 30 Days
Over the last 30 days, rainfall was above average
over pockets in the West Africa and central
Africa. In the east, rainfall was above average
in western Kenya and in the western part of
Ethiopia. Rainfall was slightly below average
over eastern South Africa.
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Rainfall Patterns Last 7 Days
During the past 7 days, rainfall was below
average in parts of the Gulf of Guinea region,
while sectors in East Africa, including Kenya and
Uganda received above average rains. The
southern sector of Somalia registered below
average rainfall.
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Recent Rainfall Evolution

• Over the last 30 days, rainfall continued to be
  above average over the western part of the Sahel
  (bottom panel left). Rainfall was also above
  average over portions of eastern Africa (bottom
  panel right). Rainfall was below average over
  western Ethiopia (upper panel right).

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Atmospheric CirculationLast 7 Days
Over the past 7 days, the 850 hPa wind anomaly
(left panel) featured weak westerly anomalies in
the Gulf of Guinea with on-shore flow into
Nigeria and a band of northerlies over the
central portion of north Africa. Also featured is
a cyclonic circulation over the central Indian
Ocean. The 200hpa wind anomaly featured a
westerly anomaly over the Equatorial Atlantic and
a weak easterly anomaly over western Indian Ocean
into Eastern Africa.
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Weekly Precipitation Climatology
Based on CPC daily precipitation analysis for the
period 1979-present, much of the rainfall
in Africa during the periods 28 Oct 3 Nov and
4-10 Nov occurs In central Africa in the
Congo Basin, and in the Greater Horn of Africa in
the areas encompassing Kenya,
northwestern Tanzania, Uganda, and southern Sudan.
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NCEP GEFS Model ForecastsNon-Bias Corrected
Probability of precipitation exceedance Week-1
Valid 28 October 3 November, 2008Week-2 Valid
4 - 10 November, 2008
For week-1, the global ensemble forecast system
(GEFS) suggests 90 chance for precipitation to
be above average over portions of central Africa,
including northern DRC, Congo, and Gabon. There
is a 90 chance or above for precipitation to
exceed 50 mm over parts of Ethiopia. For week-2,
there is a high chance for precipitation to
exceed 50 mm over the eastern half of DRC, parts
of Congo, and Gabon. Note The GFS tends to suppr
ess (increase) precipitation in the Sahel (Gulf
of Guinea region).
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Experimental Week-1 Week-2 Precipitation
Outlook
Week-1 Outlook Valid 2 October 3
November, 2008
Climatology is expected across the Congo Basin
and the Greater Horn of Africa
The active phase of the MJO currently centered
over the western Pacific far away from
Africa, and conflicting local signals including
moisture convergence in the Congo
basin will increase the chance for average
rainfall in central Africa and in the Greater
Horn of Africa (see slide 11).
Week-2 Outlook Valid 4-10 November, 2008
Climatology is expected across the Congo Basin
and the Greater Horn of Africa
The active phase of the MJO currently centered
over the western Pacific far away from
Africa, and conflicting local signals including
moisture convergence in the Congo
basin will increase the chance for average
rainfall in central Africa and in the Greater
Horn of Africa (see slide 11).
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Summary

• During the past 7 days, portions of West Africa,
  including the western and central sectors of the
  Sahel continued to register moderate to heavy
  rains. The late rains can be damaging to already
  harvested crops but kept on the ground. In
  contrast, rainfall was below average over the
  eastern part of the Gulf of Guinea region. Light
  to moderate rains fell over much of the central
  African rains. Much of Cameroon, CAR, and the
  northern areas of Gabon, Congo, and DRC received
  below average rainfall, wile southwestern DRC,
  central and southern Congo, and eastern Gabon
  received above average rainfall. The eastern
  sector of the Greater Horn of Africa, including
  southern Sudan, Uganda, and western Kenya
  received beneficial rains as totals average 15 to
  50 mm above the mean. The southern part of
  Somalia received below average rainfall.
• Over the last 30 days, the recent rains sustained
  moisture surpluses over portions of western East
  Africa, including western Kenya, parts of the
  Lake Victoria Basin, and southern Sudan.
  Rainfall also continued to be above average over
  pockets in the western part of the Sahel,
  including southeastern Senegal and western Mali.
• For the week1 ending 27 October , there is an
  increased chance for above average rainfall over
  the Congo Basin. For week2 climatology is
  expected.