African Centre of Meteorological Application for Development Centre Africain pour les Applications de la Météorologie au Développement

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1 African Centre of Meteorological Application for Development Centre Africain pour les Applications de la Météorologie au Développement Ten Day Climate Bulletin N 4 Dekad 1 st to 10 th February 2013 HIGHLIGHTS: Significant precipitation amounts were recorded over much of Zambia northern part of Mozambique and south-west Madagascar. The highest cumulative precipitation (86.4mm) is observed at Port Elizabeth in Southern African region. Highest temperature with a maximum of 36.3 C prevailed at Khartoum (Sudan) and the lowest minimum of 2.4 C was observed at Nouakchott in Mauritania. In the Outlook, Probability of precipitation exceeding 100mm is likely to prevail at the eastern Angola, northeast Zambia south of the DRC, and northern Madagascar. 1. GENERAL METEOROLOGICAL SITUATION Subsection 1.1 provides the strengths of the surface: pressure systems and ITD, CAB and ITCZ displacements, while subsection 1.2 is on Troposphere and gives a brief on monsoon, dust loading and surface concentrations, thermal index regimes and the relative humidity. 1.1 SURFACE Pressure Systems The Azores high of 1030hPa has strengthened by 3hPa compared to the previous dekad and by 10hPa in relation to the climatological mean ( ). The centre was located at about 32ºN/20ºW over North Atlantic Ocean. St. Helena high of 1029 hpa, has strengthened by 8hPa compared to the previous dekad and by 10hPa in relation to the climatological mean ( ). Its centre is located around 32 S/0 W at south of the Atlantic Ocean. Mascarene high of 1028 hpa has strengthened by 3 hpa compared to the previous dekad. However, it has strengthened by 9 hpa in relation to the reference period Its centre was located at about 35 S/94 E over southern Indian Ocean. The Thermal Low had two cells of 1010hPa and has deepened by 2hPa compared to the previous dekad. Their centres are located at 10 N/20 W over central Chad and 8 N/30 E over central part of South Sudan. Fig.1a : Pressure at MSL 1 to 10 February 2013 (source NOAA/NCEP ) Fig. 1b: Pressure Anomaly at MSL 1 to 10 February 2013 (source NOAA/NCEP) 1

2 1.1.2 Inter-Tropical Discontinuity (ITD), Inter-Tropical Convergence Zone (ITCZ) and Congo Air Boundary (CAB) Between the 1 st dekad of February 2013 (black line), and 3 rd dekad of January 2013 (blue line), the ITD has moved southward by about 1 to 3 degrees over north Atlantic Ocean, south of the Gulf of Guinea countries, north of DRC passing through extreme south of Cameroon and CAR. The Meridional arm remained quasi-stationary over Uganda and eastern Tanzania. The Inter-Tropical Convergence Zone (ITCZ) shifted downwards about 1 to 2 degrees over the Mozambican channel (Figure 2). Fig. 2: The mean position of ITD, CAB and ITCZ 1 st dekad of February (black), 3 rd dekad of January 2013 (blue) The red and green triangles represent their maximum and minimum displacements respectively. 1.2 TROPOSPHERE African Monsoon At 925 hpa level, the intensity of the monsoon winds was weak (2 m/s) over southern Cameroon, much of Gabon and Equatorial Guinea. The intensity of the monsoon is very weak over much of the Central African region at 850 hpa level (Figures 3a & 3b). Fig. 3a: Mean wind at 925 hpa in m/s 1 to 10 February 2013, (Source: NOAA/NCEP) Fig. 3b: Mean wind at 850 hpa in m/s 1 to 10 February 2013, (Source: NOAA/NCEP) 2

3 1.2.2 Dust loading particles The map below (Figure 4a) shows low dust loading ranging from 0.1 to 0.4g:/m 2 over much north Africa, Gulf of Guinea countries (GoG), Sahelian countries and northern part of Central African countries. However, moderate dust loading ranging between 0.4 to 0.8g/m 2 prevailed over western Chad and northern Libya Dust Surface Concentration Figure 4b shows low dust surface concentrations ranging between 5 to 50 µg:/m 3 over extreme south of the coastal part of (GoG) countries, much of Central African Republic (CAR) and Ethiopia, south-east Algeria, extreme north of Morocco and Algeria. Moderate concentrations (50 to 200 µg/m 3 ) prevailed over, northern African countries, much of the GoG countries and East Africa. The highest concentrations of 200 to 500 µg:/ m 3 were observed over northern Mauritania, east and central Morocco, south, north-east and western Algeria, central Tunisia, northern Libya, north-east Ethiopia and Nigeria, western Chad with peak of 2000 µg/ m 3 µg/ m 3 over eastern Tunisia, north-east Libya and north-west Chad (figure 4b). Fig. 4a: Dekadal Dust loading (g/m2) 1 to 10 February 2013 (Source WMO SDS-WAS: BSC-DREAM8b) Fig. 4b : Dekadal Surface Dust Concentration (μg/m 3 ) 1 to 10 February 2013, (Source WMO SDS-WAS: BSC-DREAM8b) Thermal Index (TI) Regime During the first dekad of February, 2013, the Thermal Index (TI) regime at 300hPa in (Figure 5a) had isotherm value of 242 K over Guinea-Conakry, Sierra-Leone, Liberia, over extreme south of Burkina-Faso, central Ghana, and Nigeria, extreme north of Cameroon, south of Chad, south-east of South Sudan, east of CAR, Kenya and Ethiopia, north of the DRC and Tanzania and much of southern African countries. The high TI regime 242 K with high relative humidity 60% at 850 hpa, triggered deep convection with heavy rainfall which caused flooding and landslides over some parts. However, areas with TI value 241 K with low humidity values experienced suppressed convective activities. The analysis in figure 5b shows increase temperatures anomalies of 0 to 2.5 K compared to the normal over the entire continent except Algeria, Libya, northern part of Egypt, and South Africa. Fig. 5a: TI at 300hPa ( k ) 1 to 10 February 2013 (Source: NOAA/NCEP) Fig. 5b: TI Anomaly at 300hPa ( k) 1 to 10 February 2013 (Source: NOAA/NCEP) 3

4 Relative Humidity (RH) at 850 hpa The 850hPa level (Figure 6a) shows high RH ( 60%) during the first dekad of February, 2013 over much of central Africa and southern African countries, Ethiopia, Eritrea and Kenya. The remaining parts of the continent observed RH 40%). The RH anomalies for the dekad compared with the reference period in figure 6b is superior over most parts of north African countries, the GoG, CAR, southern Africa, Kenya, Somalia and south-east Ethiopia, whilst positive anomalies prevailed over the rest of the continent. Fig. 6a: RH (%) at 850hPa 1 to 10 February 2013 (Source: NOAA/NCEP/ESRL: PSD) Fig. 6b: RH Anomaly at 850hPa 1 to 10 February2013, (Source: NOAA/NCEP/ESRL: PSD) Relative Humidity (RH) at 700 hpa The first dekad of February, 2013 has observed high RH 60% at 700hPa (Figure 7a) over much of Central Africa and southern African countries and over Ethiopia. The rest of Africa observed RH less than or equal ( ) to 40%. The parts with threshold RH ( 60%) were very favorable for deep convection which generated rainfall with high impact like in precipitation figure 8. The RH anomalies (Figure 7b) is less than the reference period ( ) over much of the continent except southern Chad, most of Central Africa and southern African countries,great Horn of Africa (GHA), coastal part of west Africa and south of Tunisia. 2. PRECIPITATION AND TEMPERATURE SITUATION Section 2.1 provides a summary on estimated precipitation amounts and distribution. 2.1 PRECIPITATION The precipitation estimate based on satellite and rain gauge observations in figure 8, shows significant precipitation amounts over part of Central Africa and southern African countries. In detail: 2.1 PRECIPITATIONS Northern Africa countries: observed precipitation amounts ranging between 10 and 75mm over Algeria and Tunisia with maximum of 100mm over Tunisia. 4

5 The Sahel: observed no significant precipitation. Gulf of Guinea countries: observed precipitation amounts ranging between 20 and 50mm over south-east of Liberia and south-west of Ivory-Coast. Central Africa countries: recorded cumulative precipitation amounts ranging between 20 to 75mm with maximum values ranging between 75 and 100mm over southern Gabon and Congo. GHA countries: observed cumulative precipitation amounts ranging between 10 to 50mm with peaks ranging between 50 and 75mm over southern Tanzania. Southern Africa countries: observed significant precipitation amounts ranging between 20 and 75mm with peaks ranging between 100 and 200mm over much of Zambia, north of Mozambique and south-east Madagascar. Figure 8: Cumulative Estimated Precipitation 1 to 10 February 2013 (Source : NOAA/NCEP) 2.2 Observed Data Table 1 below shows that the highest amount of precipitation (86.4 mm) was recorded at Port Elisabeth at sothern African region. The highest maximum temperature of 36.3 C was observed at Khartoum (Sudan) and the lowest minimum temperature of 2.4 C was observed at Nouakchott (Mauritania). 5

6 Table 1: Dekadal total values: Precipitations, Number of rainy days, Mean Minimum and Mean Maximum température. PS PAN PGG STATIONS Précipitations (mm) Nombre de jours de pluies Moyenne minimale de température. ( C) Moyenne maximale de température. ( C) Algier (Dar El Beida) Tunis Tripoli Cairo Casablanca Tamanrasset Nouakchott Dakar-Yoff Tombouctou Banjul Bamako-Sénou Ouagadougou Bobo Dioulasso Bilma Agadez Niamey-Airport Zinder N Djamena Abidjan Accra Lomé Cotonou PAC Douala Bangui Libreville Brazzaville PCA PAA POI Khartoum Nairobi Dodoma Kigoma Dar-es-Salaam Mbeya Mtwara Nampula Lusaka Harare Bulawayo Windhoek Maputo Beira Ghanzi Francistown Seretse Kama Manzini Johannesburg Pretoria Port Elisabeth Durban Cape Town Seychelles Antsiranana Antananarivo Toalagnaro Plaisance (Source: ACMAD /GTS) NOTE: 0 means no rain; - means no temperature data available NAC= Northern Africa Countries; SC=Sahel Countries; GGC=Gulf of Guinea Countries; CAC=Central Africa Countries; GHA=Greater Horn of Africa Countries; SAC=Southern Africa Countries; IOC=Indian Ocean Countries. 6

7 3. Outlook valid for 18 to 24 February Precipitation Moderate to heavy precipitation is expected during the 18 to 24 February 2013 over southern Angola, northern Zambia, south of DRC and much of Madagascar (figure 9a). Probability of precipitation exceeding 100mm is expected over eastern Angola, north-east Zambia, south of DRC, and northern Madagascar. North Africa: Majority of the countries in this region did not record precipitation except over extreme north of Morocco where precipitation between 10 to 20mm will be observed. The Sahel: No significant precipitation will be observed Gulf of Guinea countries: precipitation amounts ranging from 10 to 40 mm will be observed over southern part of the domain. Central Africa countries: precipitation amounts ranging from 10 to 75 mm will be observed over greater part of the region with peak of 200mm at the extreme south of the DRC. GHA countries: will observe precipitation amounts more than 100mm over Tanzania. Southern Africa countries: Precipitation amounts ranging between 10 to 100mm will prevail with peaks more than 250mm predicted over Zambia and south of Angola. Fig. 9a : Probability forecast of total precipitation(mm) 18 to 24 February 2013 (Source : NCEP/GFS) Fig.9b : Probability forecast of total precipitation exceeding 75mm, 18 to 24 February 2013 (Source: NCEP/GFS) 3.2 Temperature The forecast in figure 10a shows that mean surface temperature will be 20 C to 25 C over north of the Sahelian countries and 25 to 30 C over the southern part. However, temperatures predicted between 30 7

8 and 35 C will be observed over southern Chad. The greater part of the GoG countries will record temperatures between 25 to 30ºC. Temperatures ranging between 25 to 30ºC, except over the southern part of DRC, where temperatures will range between 20 and 25 C. The GHA countries will record temperatures between 10 et 35 C with lowest temperature (10-20 C) over the Ethiopian highlands, north-west Sudan, and the highest value more than 35 C at south east of South, extrem north of Kenya, southern Ethiopia and Somalia. Temperatures between 15 et 25 C will be observe over much of southern, except Namibia, Botswana and north-wset of South Africa and the lowest ranging between 10 to 15 C will prevail over Lesotho. Negative anomalies (figure 10b) will be observe over northern Sahel, eastern Cameroon, southern Gabon, and DRC,northern Zambia and the great lakes region. Negative to neutral temperature anomalies will be observed over part of southern African countries, much of Madagascar and over the Ethiopian highlands. Neutral to positive anomalies will be observed over north of the GoG countries, Kenya and Congo, much of Namibia, Botswana, western part of South Africa, over CAR, South Sudan, south of Chad, eastern Ethiopia and Somalia (Figure 10b). Fig. 10a: Mean surface temperature forecast 18 to 25 February 2013, (Source: COLA) Fig. 10b: Temperature Anomaly forecast 18 to 25 February 2013, (Source: COLA) 3.3 Soil Moisture The outlook of soil moisture change (figure 11b) show increase in soil humidity over Liberia, central Ivory- Coast and Ghana, extreme south of Nigeria and Zambia, Tanzania and Madagascar, extreme south-west of Cameroon, south-east Gabon and Angola, central of Congo Brazzaville, much of DRC and northern Namibia. 8

9 Fig. 11a: Initial Soil moisture 18 to 25 February 2013 (Source: COLA) Fig. 11b: Soil moisture change 18 to 25 February 2013 (Source: COLA) 9