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									May 2012                                                                     No. ICPAC/02/243



IGAD Climate Prediction and Applications Centre Monthly Bulletin, May 2012

1.       HIGHLIGHTS/ ACTUALITES

        In April 2012, significant rainfall activities were reported over eastern parts of
         southern sector; much of the equatorial sector excluding eastern parts; and southern
         parts of the northern sector of the Greater Horn of Africa (GHA) region.
        The regional consensus climate outlook for the June to August 2012 rainfall season
         indicates increased likelihood of near normal to above normal rainfall over western
         and central areas of the northern sector as well as the western and coastal parts of the
         equatorial sector of GHA;
        The rainfall conditions during April 2012 resulted in flooding; landslides; destruction
         of infrastructure, crops and property; loss of lives, and increase in water related
         diseases.


2. INTRODUCTION

In this bulletin, a review of the climate conditions for April 2012 and the climate outlook for
June to August 2012 period over the Greater Horn of Africa (GHA) are provided. The socio-
economic impacts associated with both the observed climate conditions and climate outlook
are also highlighted.

The bulletin consists of seven sections. Section 1 provides the major highlights of the climate
conditions while the overall summary given in section 3. In section 4, the prevailing climate
patterns in April 2012 are discussed while section 5 discusses the dominant weather systems.
The climate outlook for June-July-August 2012 period over GHA region is presented in
section 6. A summary of socio-economic impacts associated with the observed climate
conditions and those expected from the climate outlook are presented in the final section.


3. SUMMARY / RESUME

A summary of the three main components of this bulletin is provided in this section. These
components are the observed climatic conditions over GHA in April 2012; the climate
outlook for June-July-August 2012 period; and the impacts associated with both the observed
climate conditions and the climate outlook.

During the month of April 2012, significant rainfall activities were reported over the eastern
parts of southern sector; much of the equatorial sector excluding eastern and northern coast of
Kenya and southern Somalia; and south-western and north-eastern parts of Ethiopia. The
observed rainfall conditions resulted flooding, landslide, increase in water related diseases as
well as prospects of improved agricultural and livestock production.

The regional consensus climate outlook for the June to August 2012 rainfall season indicates
increased likelihood of near normal to above normal rainfall over western and central areas
of the northern sector of GHA as well as the western and coastal parts of the equatorial
sector. For the rest of GHA, June to August period is a dry season and these areas are


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expected to remain generally dry during June to August 2012.

World Meteorological Organisation (WMO) and the major climate centres have noted the
warming of SSTs in the equatorial Pacific Ocean with potential occurrence of neutral to
warm event towards the end of the year. Indian Ocean Dipole (IOD) circulations that also have
significant influence on regional climate are expected to contribute to anomalies in regional
rainfall anomalies over the rest of the year. Positive (negative) IOD circulation has been
associated with enhanced (reduced) advection of moisture into the eastern parts of the sub region
from Indian Ocean. El Niño is normally associated with floods in the equatorial areas within
October-February months. El Niño has also been associated with droughts in the northern and
southern sectors of GHA. Updates on El Niño will be provided regularly by WMO, the
major global climate centres, ICPAC and NMHSs among other climate institutions.


4.      CLIMATE PATTERNS IN APRIL 2012

The climatological summary for the rainfall amounts and rainfall severity indices over the
GHA in April 2012 are provided in this section. The rainfall severity indices are derived
only for those areas in the GHA region where April is not a dry month.

4.1 Rainfall amounts and performance during April 2012

Significant rainfall activities were reported over much of equatorial sector, southern Ethiopia
and coastal parts of Tanzania in the month of April 2012. Rainfall amounts ranging from
100mm to more than 200mm were reported over northern and south-western Ethiopia; much
of Rwanda, Burundi and Uganda; most parts of Kenya excluding the eastern part and
northern coast; and northern and coastal parts of Tanzania (Figure 1). Less than 50mm of
rainfall were received over south-western Tanzania; northern coast of Kenya; southern and
northern Somalia; and much of northern and central Ethiopia during April 2012. The rainfall
data for South Sudan, Sudan, Eritrea and Djibouti was not available for analysis.




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Figure 1: Spatial distribution of rainfall during April 2012 (Distribution spatiale de la
        pluviométrie pour le mois d’avril 2012)

4.2 Climate severity

Rainfall severity indices are derived by considering all observations which are less than
25% (first quartile) of the ranked historical records to be dry while those which are more
than 75% (third quartile) are considered wet.

In Figure 2, the spatial pattern of the rainfall severity index over the GHA for the month of
April 2012 is shown. Dry conditions were recorded over north-western Ethiopia; much of
Somalia; eastern and northern coast of Kenya; south-western and southern Tanzania. Near
normal to wet conditions were reported over much of Rwanda, Burundi, and Uganda;
northern and central Tanzania; western, central, northern and southern Kenya; and much of
Ethiopia during the month of April 2012 (Figure 2). The data for South Sudan, Sudan, Eritrea
and Djibouti was not available for analysis.




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Figure 2: Rainfall severity index for April 2012 (Indice de rigueur de la pluviométrie en avril
          2012

4.2.1 Cumulative climate stress severity monitoring
The extent of climate-related impacts on any particular system depends on the severity and
duration of the climate stress. Cumulative climate stress severity has direct and indirect
severe impacts on food security, water resources, health, livestock and many other socio-
economic sectors. The indices used to monitor cumulative rainfall severity over GHA are
presented in this section.

4.2.2 Cumulative rainfall performance from June 2011 to April 2012

Cumulative rainfall performance for some selected stations over GHA from June 2011 to April
2012 is shown by Figure 3. Near normal to slightly enhanced rainfall conditions have been
observed over the southern sector (Figure 3a) and western parts of the equatorial sector (Figure
3b). Depressed rainfall conditions have prevailed over the eastern parts of the equatorial sector
of the GHA since June 2011 to April 2012 (Figure 3c).




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  Figure 3a: Cumulative rainfall series for Sumbawanga (séries de pluviométrie cumulée pour
                                          Sumbawanga)




    Figure 3b: Cumulative rainfall series for Masindi (séries de pluviométrie cumulée pour
                                            Masindi)




    Figure 3c: Cumulative rainfall series for Mombasa (séries de pluviométrie cumulée pour
                                            Mombasa)


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4.3 Rainfall anomalies

4.3.1 Rainfall anomalies during February to April 2012

The spatial pattern of the observed rainfall anomalies for the February-March-April 2012
period over GHA is shown by Figure 4. Less than 75% of the expected rainfall totals for the
February to April period was received over southern, coastal and western parts of Tanzania;
the eastern block of Kenya; much of Somalia and Ethiopia excluding south-western Ethiopia
(Figure 4). South-western Ethiopia; western block of Kenya; much of Uganda, Rwanda and
Burundi; northern, central and south-eastern Tanzania received between 75% and 125% of
their long-term mean rainfall for the three months’ period. An isolated parcel over south-
western Ethiopia was the only location that exceeded 125% by recording between 125% and
175% of the expected rainfall totals for the February to April period. Rainfall data for
February and April 2012 over Sudan; South Sudan; Eritrea and Djibouti was not available for
analysis.




Figure 4: Rainfall anomalies for February to April 2012 (Anomalies de la pluviométrie pour la
          période allant de février à avril 2012)

4.4        Temperature anomalies

4.4.1 Maximum temperature anomalies

During the month of April 2012, warmer than average maximum temperatures were recorded
over much of equatorial and southern sectors (Figure 5a). Eastern Kenya; parts of southern
Somalia; western and eastern Ethiopia recorded positive anomalies of maximum temperatures



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greater than 2°C. Cooler than average maximum temperatures were recorded over northern
tip of Ethiopia; parts of south coast, north-western and western Kenya; eastern and south-
eastern Uganda; parts of northern, central and north coast of Tanzania; and eastern Rwanda in
April 2012. Maximum temperature data for April 2012 over Sudan; South Sudan; Eritrea and
Djibouti was not available for analysis.
.




Figure 5a: Maximum temperature anomalies for April 2012 (Anomalies de température
          maximum pour le mois d’avril 2012)
4.4.2 Minimum temperature anomalies

Negative minimum temperature anomalies were recorded over southern Tanzania; north-
western Kenya; and south-western Ethiopia in the month of April 2012. Much of the
remaining parts of equatorial and southern sectors as well as Ethiopia recorded warmer than
average minimum temperature anomalies (Figure 5b). Positive minimum temperature
anomalies greater than 2°C were recorded over central and southern Ethiopia; south-western
and northern Uganda; northern Rwanda and western Kenya. Minimum temperature data for
April 2012 over Sudan; South Sudan; Eritrea and Djibouti was not available for analysis.




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     Figure 5b: Minimum temperature anomalies for April 2012 (Anomalies de température
                           minimum pour le mois d’avril 2012)


5.          STATUS OF THE CLIMATE SYSTEMS

WMO and major climate centres indicate that 2011/12 La Niña has ended, and that La Niña
conditions in the tropical Pacific transitioned to neutral (neither El Niño nor La Niña)
conditions in early April 2012 (Figure 6). Cooler than average SSTs were observed over
tropical Atlantic Ocean and warmer than average SSTs over southern and eastern Indian
Ocean (Figure 6). The Indian Ocean Dipole (IOD) remained positive (Figure 7).




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Figure 6: Sea Surface Temperature anomalies for April 2012 (Courtesy of NOAA) (Anomalies de température
       de surface de la mer pour le mois d’avril 2012)




Figure 7: Current condition of Indian Ocean Dipole (IOD) and some analogue years (Situation actuelle du
       Dipôle de l’Océan Indien et quelques années analogues)

6.0     CLIMATE OUTLOOK FOR JUNE TO AUGUST 2012

6.1     The Regional Climate Outlook Forum

The Thirty First Greater Horn of Africa Climate Outlook Forum (GHACOF31) was convened


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from 29th to 30th May 2012 at Kempinski Palace Hotel, Djibouti, Republic of Djibouti by the
IGAD Climate Prediction and Applications Centre (ICPAC) and partners to formulate a
consensus regional climate outlook for the June to August 2012 rainfall season over the GHA
region. The GHA region comprises Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda,
Somalia, South Sudan, Sudan, Tanzania and Uganda. Users from sectors such as health, disaster
risk management, gender, civil society, agriculture and food security, water resources and
media, as well as non- governmental organisations and development partners actively
participated in the formulation of applications and impacts of the climate forecast in their
specific sectors. The forum reviewed the state of the global climate system including ENSO-
neutral conditions, sea surface temperatures (SSTs) over Atlantic and Indian Oceans, especially
the Indian Ocean Dipole (IOD) circulation as well as low and medium level atmospheric
circulation. The associated impacts on the GHA during June to August 2012 rainfall season
were considered.

Guidance and valuable forecast information was drawn from a wide range of sources including
the World Meteorological Organisation’s Global Producing Centres (WMO GPCs) and National
Meteorological and Hydrological Services. These inputs were combined using deterministic and
probabilistic modelling alongside expert analysis and interpretation to obtain the regional rainfall
forecast for the period June to August 2012.


6.2     Rainfall Outlook for June to August 2012


The rainfall outlook for various zones within the GHA region is given in figure 1 below.




Figure 8: Climate Outlook for the June to August 2012 (Aperçu du temps pour la période de juin à août
           2011)


Zone I:     Climatology (normal conditions for the season being projected)


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Zone II: Increased likelihood of near normal to above normal rainfall

Note:

The numbers for each zone indicate the probabilities of rainfall in each of the three
categories, above-, near-, and below-normal. The top number indicates the probability
of rainfall occurring in the above-normal category; the middle number is for near-
normal and the bottom number for below-normal category. For example, in zone II ,
there is 35% probability of rainfall occurring in the above-normal category; 45%
probability of rainfall occurring in the near-normal category; and 20% probability of
rainfall occurring in the below-normal category. It is emphasised that boundaries
between zones should be considered as transition areas.


7.0 IMPACTS ON SOCIO-ECONOMIC SECTORS

The socio-economic impacts associated with observed rainfall conditions and those from the
climate outlook are provided below.

7.1 Vegetation condition indicators and associated impacts


The difference of the Normalized Difference Vegetation Index (NDVI) between March and
April 2012 indicates improved vegetation conditions over the western parts of the equatorial
sector; southern South Sudan; southern and central Ethiopia and the coastal parts of Tanzania.
The rest of region showed deteriorated vegetation conditions except improved patches over
southern Somalia (Figure 9).




                                                                            anomalies de
Figure 9: Vegetation difference between March and April 2012 over the GHA (Les
            végétation sur la Grande Corne de l’Afrique entre mars et avril 2012)


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7.2 Impacts of observed climate conditions during April 2012
The socio-economic impacts associated with the observed rainfall over the southern sector of
GHA during April 2012 are highlighted below:
    Floods, landslides, leading to loss of property and displacement of people;
    Improvement in water and pasture conditions;
    Incidences of water related diseases.


7.3 Potential impacts for June-August 2012 rainfall outlook
The areas expected to receive near normal to above normal rainfall are likely to have the
following impacts:
    • Flooding, landslides, displacement of people, and destruction of property;
    • Good prospects for high agricultural production;
    • Outbreak of water related diseases;
    • Improved conditions of pasture and water resources.




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