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CLIMATE DIAGNOSTIC
BULLETIN FOR AFRICA
N° 8
August 2013
OCEAN-ATMOSPHERE
MONITORING
&
PREDICTION
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SUMMARY AUGUST 2013
In August 2013, above normal to well above normal precipitations were observed over the eastern Mali,
northern Burkina, most part of Niger, southern Algeria and, southern Guinea and over Sierra Leone and the
Cap region in South Africa. This situation caused floods over Niger, Mali and Senegal. Well below normal
precipitations were observed over Liberia, Cote d`Ivoire and southern half Nigeria.
From June to August 2013, well above normal precipitations were observed over bordering areas of
Algeria-Mali-Niger and Guinea-Sierra Leone. Well below normal rainfalls were observed over northern
Chad, central Sudan, northern Somali, over Gabon, Congo, DRC and eastern part of Tanzania.
Otherwise, positive temperature anomalies in August, 2013 (figure 8) greater than 20k were observed over
Morocco, bordering areas of Algeria-Tunisia-Libya and Zimbabwe-Mozambique. However, Seasonal
temperature anomalies ranging between 1.5 to 20 k for June-July-August 2013 were observed over
southern Morocco, western Mauritania, central Namibia and bordering area of Zimbabwe-Mozambique.
Well below normal precipitations are expected over Sierra Leone, Liberia, Guinea, coastal
Indian of Sudan, Eritrea, Ethiopia and Somalia, Also, eastern half of Tanzania, Malawi, northern
Mozambique which experienced below normal precipitations during the last 3 months will
experience again the same situation in the next 3 months.
Well above normal precipitations will expected over Morocco, western Senegal, Guinea Bissau, over
south-east Mauritania, central Mali, western Niger, Burkina and northern Nigeria. The same situation
will be observed over bordering area bordering area of Niger-Chad-Cameroon for the seasonal
period of SON
From September to November 2013, positive temperatures anomalies at 2 meters above soil will be
expected over extreme eastern Libya, over Egypt, Djibouti, northern Sudan and Sudan.
1. SYNOPTIC SITUATION FOR AUGUST 2013
This section shows the intensity of pressure centers, the circulation and its anomalies at 850 hPa, the wind
direction and speed in the middle and higher levels, thermal regimes at high level, relative humidity at
850hPa and 700 hPa levels, the Sea Surface Temperatures (SST) and the El Nino/Southern Oscillation
(ENSO).
1.1 Pressure Centres:
Figure 1 below states the locations and status of the surface pressure systems:

The Azores high of 1026 hPa strengthened by 3hPa compared to the previous month. The
centre was located at about 38ºN/29ºW over North Atlantic Ocean.

St. Helena high of 1026 hPa strengthened by 4hPa compared to the previous month. The centre
was located at about 26ºS/8°W over South Atlantic Ocean.

Mascarene high of 1027 hPa strengthened by 3hPa compared to the previous month. Its centre
was located at about 30ºS/62ºE over southern Indian Ocean.

The Thermal Low of 1007 hPa filled by 1hPa compared to the previous. Its centre was located at
21°N/2°E over northern Mali.
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Figure 1 : Mean sea level pressure August 2013
(Source : NOAA/NCEP)
1.2 Wind Anomalies (m/s) at 850hPa
Figure 2 below shows the Wind anomalies at 850 hPa level
The strong westerly wind anomalies with speed
greater or equal to (≥ 4m/s) observed over most
part of Maghreb. Strong wind anomalies (≥ 3m/s)
prevailed over southern part of GoG countries,
over CAR, Cameroon and most of Southern
African countries. Also, the Somalian jet has been
very active during the month of August.
Figure 2: Wind anomalies (m/s) at 850 hPa August 2013
(Source : NOAA/NCEP)
1.2 Thermal Index (TI) at 300 hPa
The Thermal Index at 300 hPa level (figure 3a) for the month of March had isotherm value of 242°K over
northern Mauritania, Mali and Libya, southern Algeria extending through GoG countries to South Sudan,
Ethiopia and Somalia.
The figure 3b shows positive anomalies between 0.5 to 1°K over most of the continent except southern
South Africa and Lesotho where negative anomalies ( 0.5°k) were observed.
Figure 3a : Thermal Index at 300hPa August 2013
(Source : NOAA/NCEP)
Figure 3b : TI Anomaly at 300 hPa August 2013
(Source : NOAA/NCEP)
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1.3 Relative Humidity (RH) at 850 hPa
The high RH (≥60%) at 850 hPa (figure 4a), was observed during the month of August 2013 over central
Sahel, GoG countries, central Africa countries, Eastern Africa, northern Mozambique and Madagascar.
The RH values were greater than the mean 2002-2011 over most the continent expect Lesotho and
central-east of South Africa where negative anomalies were observed (Figure 4b).
Figure 4a : Relative humidity at 850hPa August 2013
(Source : NOAA/NCEP)
Figure 4b : Relative humidity anomaly at 850hPa August 2013
(Source : NOAA/NCEP)
1.4 Relative Humidity at 700 hPa
The high RH values (≥60%) in figure 5a, were observed over the Sahel, Central Africa, GoG, Great
Horn of Africa and northern Angola and Zambia. The regions with RH ≥60% were very favorable for
deep convection that generated heavy precipitation with high impact. The RH values in figure 5b were
greater than the normal (2002-2011) over most of the continent except over Gabon, the two Congo, Angola
and Namibia where RH values were less than the normal (2002-2011).
Figure 5a: Relative humidity at 700hPa August 2013.
(Source : NOAA/NCEP)
Figure 5b: Relative humidity anomaly at 700hPa August 2013.
(Source : NOAA/NCEP)
1.5 Sea Surface Temperature (SST) and El Nino/Southern Oscillation (ENSO)
Neutral to cool conditions were observed over the Equatorial Pacific. Warm conditions persisted over North
Atlantic Ocean at the coastal zone of the Gulf of Guinea countries and central Africa, whereby moderate to
warm conditions prevailed over the north. The SST in the Mediterranean Sea observed warm and neutral
conditions, while neutral to positive anomalies exist over the northern and equatorial part of the Indian
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Ocean with neutral to cool conditions over the south. Neutral to warm conditions persisted over south
Atlantic.
Figure 6: Sea Surface Temperature August 2013 (source: IRI)
2. CLIMATOLOGICAL SITUATION AND IMPACTS DURING AUGUST 2013
This section states the general climatological situation and its impact covering two major parameters, the
temperature and precipitation.
2.1 Precipitation
2.1.1
Monthly Precipitation
The precipitations for the month of August, 2013 (Fig. 7a) showed above normal to well above normal
precipitations over the eastern Mali, northern Burkina, most part of Niger, southern Algeria and, southern
Guinea and over Sierra Leone and the Cap region in South Africa. This situation caused floods over Niger,
Mali and Senegal. Well below normal precipitations were observed over Liberia, Cote d`Ivoire and southern
half Nigeria.
2.1.2 Seasonal Precipitation
Figure 7b indicates seasonal precipitations in percentage (June-July-August 2013). Well above normal
precipitations were observed over bordering areas of Algeria-Mali-Niger and Guinea-Sierra Leone. Well
below normal rainfalls were observed over northern Chad, central Sudan, northern Somali, over Gabon,
Congo, DRC and eastern part of Tanzania.
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Figure 7a : Monthly Precipitation in percentage for August 2013
(Source : NOAA/NCEP)
2.2
Figure 7b : Seasonal Precipitation anomaly for JJA 2013
(Source : NOAA/NCEP)
Surface Temperature
2.2.1Monthly Temperature Anomalies
Positive temperature anomalies in August, 2013
(figure 8) greater than 20k were observed over
Morocco, bordering areas of Algeria-Tunisia-Libya and
Zimbabwe-Mozambique. Negative anomalies of about
2°C were observed over bordering area of Botswana
and South Africa.
Figure 8 : Temperature anomaly August
2013, (Source : NOAA/NCEP)
2.2.2 Seasonal Temperature Anomalies
Seasonal temperature anomalies ranging between 1.5
to 20 k for June-July-August 2013 were observed over
southern Morocco, western Mauritania, central
Namibia and bordering area of ZimbabweMozambique.
,
Figure 8 : Seasonal temperature anomaly JJA
2013, (Source : NOAA/NCEP)
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3. OUTLOOK
Figure 9 and 10 shows Predicted Sea Surface Temperature (SST) anomalies and the future
characteristics of ENSO. The precipitation outlook for the coming month is also provided.
3.1 El Niño/La Niña
Figure 10 shows the forecast of dynamic and
statistical models over Niño 3.4 (5°N–5°S, 120°W–
170°W).
In mid-August 2013, majority of the dynamic and
statistical models predicted cool Southern
Oscillation (ENSO) situation for SeptemberOctober-November 2013.
Figure 10 : Ensemble multi model forecast
August 2013 (Source : IRI)
3.2 Seasonal Precipitations forecast issued on August 2013 for the period SON 2013
Foe September, October and November (SON)
2013 (figure : 11)
-Well below normal precipitations are expected
over Sierra Leone, Liberia, Guinea, coastal
Indian of Sudan, Eritrea, Ethiopia and Somalia,
Also, eastern half of Tanzania, Malawi, northern
Mozambique which experienced below normal
precipitations during the last 3 months will
experience again the same situation in the next
3 months.
-Well above normal precipitations are expected
over Morocco, western Senegal, Guinea Bissau,
over south-east Mauritania, central Mali, western
Niger, Burkina and northern Nigeria. The same
situation will be observed over bordering area
bordering area of Niger-Chad-Cameroon.
Figure 11 : Seasonal precipitation forecast for SON
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3.3 Seasonal temperature forecast issued on August 2013 for the period SON 2013
The following outlooks have issued for September,
October and November (SON) 2013
Positive temperatures anomalies at 2 meters above
soil will be expected over extreme eastern Libya,
over Egypt, Djibouti, northern Sudan and Sudan.
Figure 12: Prevision saisonnière des
températures de JAS
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