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CLIMATE DIAGNOSTIC
BULLETIN FOR AFRICA
N° 5
MAY 2013
OCEAN-ATMOSPHERE
MONITORING
&
PREDICTION
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1
SUMMARY MAY 2013
Very well below normal precipitation (drought) prevailed over southern Angola
and neighbouring area in Zambia. Precipitation for the month of May, 2013
shows above normal rainfall over parts of Benin and Togo, most parts of
Nigeria, the extreme southern part of Chad, south eastern part of Ethiopia and
over adjacent areas of Kenya and Somalia. Below normal rainfall were observed
over Angola, Zambia, Malawi, Mozambique and Madagascar.
Otherwise, temperature increase of more than 2°C in relation to the reference
period 1971-2000 prevailed over the Sahel and Sahara with peak of 3.5°C over
southern Morocco and western Mauritania.
1. SYNOPTIC SITUATION FOR MAY 2013
This section shows the intensity of pressure centers, the circulation and its anomalies at 850hPa, 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 1027hPa strengthened by 8hPa compared to the previous month and
remained quasi- stationary in relation to the climatological mean (1971-2000). The centre was
located at about 31ºW/43ºN over North Atlantic Ocean.

St. Helena high of 1020hPa strengthened by 5hPa compared to the previous month and still
strengthened by 1hPa in relation to the climatological mean (1971-2000). The centre was
located at about 4ºW/30°S over South Atlantic Ocean.

Mascarene high of 1022hPa remained as it was compared to the previous month, and was
quasi- stationery in relation to the reference period 1971-2000. Its centre was located at about
82ºE/31ºS over southern Indian Ocean.

The Thermal Low had three cells of 1009, 1008 and 1007hPa respectively. The first and second
cell remained the same compared to the previous month while the third cell filled by 1hPa. Their
centres were located at 2°E/15°N, 16ºE/14°N and 36ºE/19°N respectively over the African
continent.
Figure 1a : Mean sea level pressure May 2013
(Source : NOAA/NCEP)
Figure 1b : Mean Sea Level Pressure Anomaly May
2013 (Source : NOAA/NCEP)
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1.2 WIND ANOMALIES (m/s) AT 850hPa
Figure 2 below shows the Wind anomalies at 850hPa level
The strong westerly wind anomalies with speed
ranges between 4- 6m/s from central Algeria to
Libya and also from Gabon through Congo to
DRC. The remaining part of the continent
experienced wind speed of ≤ 2m/s.
Figure 2: Wind anomalies (m/s) at 850 hPa May 2013
(Source: NOAA/NCEP)
1.2 THERMAL INDEX (TI) AT 300hPa
The TI regime at 300hPa level (figure 3a) for the month of March had isotherm value of 242°K over Senegal,
Mali, northern Burkina Faso and Nigeria, Southern Niger, central Chad and Sudan and also Djibouti. In the
southern part of the continent it extends over Angola and Zambia, Malawi, Mozambique and Madagascar.
TI regime ≥242°K with high relative humidity (RH) ≥60% at 850hPa, triggered with heavy rainfall with floods
and landslides over some parts. However, areas with TI value ≤ 241°K and low RH experienced rainfall
deficits.
Figure (3b) shows positive anomalies between 0.5°K to 2.0°K over most of the continent except over south
of Botswana, South Africa, a small part of Egypt and Sudan where negative anomalies ( 0 to -2°) were
observed.
Figure 3a: Thermal Index at 300hPa May 2013
(Source : NOAA/NCEP)
Figure 3b: TI Anomaly at 300 hPa May 2013
(Source : NOAA/NCEP)
1.3 RELATIVE HUMIDITY (RH) AT 850hPa
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The high RH (≥60%) at 850hPa (figure 4a), was observed during the month of May, 2013 over most of
central Africa countries, most of the Great Lake Regions, most of the GOG countries, over Ethiopia,
Somalia and Madagascar. The RH values were less than the mean 2002-2011 over the GOG, the Sahel,
most of central African countries, Ethiopia and South Sudan. RH values were greater than the mean
(2002-2011) over the remaining parts of the continent (Figure 4b).
Figure 4a: Relative humidity at 850hPa May 2013
(Source : NOAA/NCEP)
Figure 4b: Relative humidity anomaly at 850hPa May 2013
(Source : NOAA/NCEP)
1.4 Relative Humidity at 700hPa
The high RH values (≥60%) in figure 5a, were observed over most of central Africa countries, most of the
GOG and the Great Horn of African countries, over Angola, Namibia and southern part Tanzania. 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 Niger and CAR, parts Morocco, Algeria, Libya, Nigeria, Chad, Mali, Mauritania, Cameroon, North/ South
Sudan, Ethiopia, Djibouti and Somalia where RH values were less than the normal (2002-2011).
Figure 5a: Relative humidity at 700hPa May 2013.
(Source : NOAA/NCEP)
Figure 5b: Relative humidity anomaly at 700hPa May 2013.
(Source : NOAA/NCEP)
1.5 SEA SURFACE TEMPERATURE (SST) AND EL NINO/SOUTHERN OSCILLATION (ENSO)
Neutral to warm conditions were observed over the central and eastern part of the Equatorial Pacific. Cool
conditions were observed over western part of the Equatorial Pacific. Warm conditions persisted over
Tropical North Atlantic Ocean. Neutral to warm conditions prevail over the Equatorial Atlantic of the Gulf Of
Guinea and Tropical South Atlantic. The Mediterranean Sea observed warm to neutral conditions prevail
over the Mediterranean Sea. Near neutral conditions prevail over much of central and western Equatorial
Indian Ocean. Slight cooling initiated off the coast of The Greater Horn of Africa.
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Figure 6: Sea Surface Temperature May 2013 (source: IRI)
2.0 CLIMATOLOGICAL SITUATION AND IMPACTS DURING MAY 2013
This section states the general climatological situation and its impact covering two major parameters, the
temperature and precipitation.
2.1 PRECIPITATION
Figures (7a and b) indicate observed precipitation estimates in percentage of normal for May and March/
April/May, 2013 respectively.
2.1.1 MONTHLY PRECIPITATION
Precipitation for the month of May, 2013 shows above normal rainfall over parts of Benin and Togo, most
parts of Nigeria, the extreme southern part of Chad, south eastern part of Ethiopia add adjacent areas of
Kenya and Somalia. Below normal rainfall were observed over Angola, Zambia, Malawi, Mozambique and
Madagascar. The remaining parts of Africa recorded normal precipitation.
2.1.2 SEASONAL PRECIPITATION
Seasonal precipitation for the months of March- April- May, 2013 (Figure 7b) showed above normal rainfall
over Benin, Togo and Nigeria, the extreme southern part of Chad cutting into a small part of CAR and also
over south eastern Ethiopia, northern Kenya and central Somalia. Below normal rainfall were observed over
parts of Angola, Zambia, Malawi, Mozambique and eastern coast of Madagascar with well below normal
rainfall recorded over southern Angola and adjacent parts of Zambia.
Figure 7a : Monthly Cumulative precipitation for May 2013
(Source : NOAA/NCEP)
Figure 7b : Seasonal Precipitation for March- April- May 2013
(Source : NOAA/NCEP)
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2.2
NEAR SURFACE AIR TEMPERATURE
ANOMALIES
The highest positive temperatures anomalies
(figure 8) ranging between 2°C to above 3.5°C
prevail over southern Morocco, western
Mauritania and Senegal, northern Libya and
Egypt, north western border of Niger/ Nigeria
and also central Namibia.
Figure 8 : Surface temperature anomaly May
2013, (Source : NOAA/NCEP)
2.2 SURFACE AIR TEMPERATURE ANOMALY FOR
MARCH-APRIL-MAY
High temperature anomalies for the months of
March- April- May with values of 20C were
observed over Senegal, Gambia and Guinea. High
negative temperature anomalies of 1.50C were
observed over western South Africa.
Figure 9 : Surface temperature anomaly for March-April-May
2013, (Source : NOAA/NCEP)
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3.0 OUTLOOK
3.1 SEA SURFACE TEMPERATURE (SST) FORECAST
Forecast for SST anomalies of June-July-August (JJA) 2013.
 Pacific Ocean: Neutral to cool temperature
conditions will be prevail over the eastern
Equatorial Pacific and near neutral to warm
temperatures will prevail over much of
central and western Equatorial Pacific. Near
neutral conditions are more likely over Enso
region.
 Atlantic Ocean: Warm conditions will persist
over Tropical North Atlantic and near neutral
conditions are expected over much of
Equatorial and southern Atlantic Ocean.

Indian Ocean and the Mozambique
Figure 10: Forecasted Surface Ocean Temperatures for May 2013
Channel: Near neutral conditions will
(Source : IRI)
prevail over Equatorial and south western
Indian Ocean.
3.2 El Niño/La Niña
Figure 11 shows the forecast of dynamic and
statistical models over Niño 3.4 (5°N–5°S,
120°W–170°W).
In July 2013, majority of the dynamic and
statistical models predicted near neutral
Southern Oscillation (ENSO) situation for JuneJuly-August, 2013.
Figure 11 : Ensemble multi model forecast
May 2013 (Source : IRI)
Figure 10 and 11 shows Predicted Sea Surface Temperature (SST) anomalies and the future
characteristics of ENSO. The precipitation outlooks for the coming months are also provided.
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3.3 PRECIPITATION OULOOK
Figure 12: Seasonal Precipitation Forecast for June- July- August,
2013
(Source: NOAA/NCEP)
3.3.1 PRECIPITATION OUTLOOK FOR JUNE- JULY- AUGUST
Below average precipitation is very likely over Equatorial Guinea, coastal parts Cote d’Ivoire, Ghana, Togo,
Benin, Cameroon and Gabon and also over the eastern parts of Tanzania, Mozambique, Kenya and
Madagascar. Near to above average precipitation is more likely in central and west part of Sahel region.
Figure 13: Seasonal Precipitation Forecast for July- August- September,
2013 (Source: NOAA/NCEP)
3.3.2 PRECIPITATION OUTLOOK FOR JUNE- JULY- AUGUST
Below average precipitation is very likely over coastal part Guinea Gulf, easternmost part of Sahel region,
south of Sudan, north of south Sudan, coastal part of central Africa and many eastern Africa countries. Near
to above average precipitation is more likely in central and west part of Sahel region.
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