African Centre of Meteorological Applications for Development Centre Africain pour les Applications de la Météorologie au Développement Ten Day Climate Watch Bulletin N 34 Dekad 1 st to 10 th December, 2015 HIGHLIGHTS Above to well above average precipitation was observed over central DRC, southwestern Ethiopia, eastern Uganda, western Kenya, northern Tanzania, southern Angola, northern Namibia and Madagascar. However, below to well below average precipitation was observed over extreme southern Liberia and Côte d Ivoire, southern Cameroon, most of Gabon, northern DRC, eastern Kenya and Tanzania, most of Mozambique, Malawi, Zambia, Zimbabwe, South Africa and western Madagascar. During the period 14 to 20 December, 2015, precipitation ranging from 10 mm to 30 mm is very likely over most of Gabon, central Congo and DRC, southern Uganda and Kenya, most of Tanzania, Botswana and South Africa, central Angola and southern Zambia. Precipitation ranging from 30mm to 50mm is likely over southern Congo, DRC, Tanzania, Malawi and Zimbabwe, northern Angola and Mozambique, central Zambia and Madagascar. Greater than or equal to 75mm precipitation is likely over southern DRC, northern Zambia and Madagascar. During the period 21 to 27 December, 2015, precipitation ranging from 10 mm to 30 mm is very likely over southern Gabon, most of Congo DRC, Tanzania, Zimbabwe, Mozambique and Botswana, central Angola, southern Uganda, Kenya, Zambia and Madagascar. Precipitation ranging from 30mm to 50mm is likely over southern Congo, DRC and Tanzania, northern Angola, Zambia and Madagascar, eastern South Africa and most of Malawi. Greater than or equal to 75mm precipitation is likely over central Zambia and Malawi. 1
1.0 GENERAL CLIMATOLOGICAL 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 and relative humidity thresholds. 1.1 SURFACE 1.1.1 Pressure Systems The Azores High of 1033 hpa, weakened by 2hPa compared to the previous dekad, but strengthened by 12hPa compared to climatological mean (1981-2010). It was located at 09 W/46 N in North Atlantic Ocean. St. Helena High of 1019 hpa, weakened by 4 hpa compared to the previous dekad, but remained stable compared to climatological mean (1981 to 2010). It was located at 07 W/32 S in South Atlantic Ocean. Mascarene High of 1024hPa weakened by 2 hpa compared to the previous dekad, but strengthened by 4 hpa in relation to climatological mean (1981-2010). It was located at 98 E/36 S in South Western Indian Ocean. The Thermal Low of 1011hPa filled by 2 hpa compared to the previous dekad. It was located at 21 E/0 N over central DRC. Fig. 1a: Mean Pressure at MSL 1 st to 10 th December, 2015 (Source NOAA/NCEP) Fig. 1b: Anomaly of Mean Pressure at MSL 1 st to 10 th December, 2015 (Source NOAA/NCEP) 1.1.2 Inter-Tropical Discontinuity (ITD), Inter-Tropical Convergence Zone (ITCZ) and Congo Air Boundary (CAB) Between the third dekad (blue line) of November and the first dekad (black line) of December, 2015 the ITD moved southward by 4 degrees over North Atlantic, central Sierra Leone, eastern Guinea, Côte d Ivoire, Ghana, Togo, Benin, Nigeria, Cameroon, CAR and South Sudan. The CAB remained quasi stationary over Uganda, Tanzania and DRC, while the ITCZ moved southward by 3 degrees over Indian Ocean. Figure 2: The mean position of ITD, CAB and ITCZ 1 st dekad (black) of December, 3 rd dekad (blue) of November, 2015 The red and green triangles represent their maximum and minimum displacements respectively. 2
1.2 TROPOSPHERE 1.2.1 African Monsoon At 850hPa level (Figure 3a), moderate northerlies were observed over northern Libya and Egypt, veering to easterlies over Chad, Niger, Algeria, Mali, Mauritania, Gulf of Guinea and Central Africa countries while weak easterlies dominated the southern African countries. The moderate to strong diffluent south easterlies and north easterlies prevailed over south western part of eastern Africa region reducing prospects of heavy rainfall. At 700 hpa (Fig.3b), moderate north-westerlies were observed over North Africa, while moderate easterlies prevailed over Gulf of Guinea, central Africa and Greater Horn of Africa countries with the dominance of the equatorial confluence. Weak moderate high Fig.3a: Mean wind at 850 hpa ( m/s) 1 st to 10 th December, 2015 (Source: NOAA/NCEP) Weak moderate high Fig.3b: Mean wind at 700 hpa (m/s) 1 st to 10 th December, 2015 (Source: NOAA/NCEP) 1.2.2 Dust loading particles Figure 4a shows low dust loading ranging from 0.1 to 0.4g/m 2 over southern Algeria and Morocco, parts of the Sahel, most of CAR and Sudan. High dust loading ranging between 0.4 to 1.2 g/m 2 was observed over southern Mauritania, central Mali, Niger and Chad. The highest dust loading ranging between 1.2 to 6.4 g/m 2 prevailed over most of Gulf of Guinea countries, Burkina Faso, southern Mali and Niger, and western Chad. Fig. 4a: Dekadal Dust loading (g/m2) 1 to 10 December 2015 (Source: WMO SDS-WAS: BSC-DREAM8b) 3
1.2.3 Surface Dust Concentration Figure 4b shows low surface dust concentrations ranging between (5 to 50µg/m 3 ) over parts of Algeria, Libya, Egypt, Sudan, Ethiopia, South Sudan and CAR. Moderate concentrations (50 to 200µg/m 3 ) prevailed over northern Mauritania, southern Morocco and Algeria and most of Sudan. The concentrations of 200 to 500 µg/ m 3 were observed over southern Mauritania and Mali, most of Senegal, Sierra Leone and Liberia, southern Côte d Ivoire and Ghana and northern Niger. The highest concentrations of above 500 to 2000 µg/ m 3 prevailed over Guinea, Burkina Faso, Togo, Benin, southern Niger, Cameroon, Nigeria and western Chad. Fig. 4b : Surface Dust Concentration (μg/m 3 ) 1 to 10 December 2015 (Source: WMO SDS-WAS: BSC-DREAM8b) 1.2.4 Wind at 200 hpa. During the first dekad of December, 2015 strong westerly winds at 200 hpa were observed over North Africa, the Sahel, Gulf of Guinea, Southern Africa countries, while light to moderate westerly winds were observed over central and eastern Africa countries. Figure 3a: Mean wind at 200hPa in m/s 1 st to 10 th December 2015 (Source: NOAA/NCEP) 4
1.2.5 Relative Humidity (RH) at 850 hpa The 850hPa level (Figure 6a) had high RH value ( 60%) during the first dekad of December, 2015, over most of Libya, Gulf of Guinea countries, Central Africa and eastern Africa countries, most of Angola, Malawi and Zambia, eastern South Africa and most of Madagascar. Low RH values ( 40%) (Figure 6a), were recorded over North Africa, the Sahel and western parts of Southern Africa. The RH anomalies for the first dekad of December, 2015 compared to the reference period 2002-2011 (Figure 6b), were positive over most of the continent except over Morocco, Algeria, Mauritania, Nigeria, Cameroon, Somalia and Southern Africa countries where negative anomalies of RH were observed. Fig. 6a: RH (%) at 850hPa 1 st to 10 th December 2015(SOURCE/.NOAA/.NCEP-NCAR/.CDAS1) Fig. 6b: RH Anomaly at 850hPa 1 st to 10 th December 2015 (SOURCE/.NOAA/.NCEP-NCAR/.CDAS-1) 1.2.6 Relative Humidity (RH) at 700hPa High RH values ( 60%) at 700 hpa (Figure 7a) were observed over extreme south eastern Gulf of Guinea, Central Africa, Greater Horn of Africa (GHA) countries, Angola, Zambia, Malawi and northern Mozambique. RH values 40% were observed over North Africa, the Sahel and South Africa. The RH anomalies for the first dekad of December, 2015 compared to the reference period 2002-2011 (Figure 6b), were negative over most of the continent except DRC, Ethiopia, Uganda, Kenya, Angola, Namibia and Botswana where positive anomalies dominated. Fig. 7a: RH (%) at 700hPa 1 st to 10 th December 2015 (SOURCE/.NOAA/.NCEP-NCAR/.CDAS1) Fig. 7b: RH Anomaly at 700hPa 1 st to 10 th December 2015 (SOURCES/.NOAA/.NCEP-NCAR/.CDAS-1) 5
2.0 PRECIPITATION Figure 8 indicates observed precipitation estimates in percentage of normal for the 1 st dekad of December, 2015. 2.1 Precipitation Above to well above average precipitation was observed over central DRC, southwestern Ethiopia, eastern Uganda, western Kenya, northern Tanzania, southern Angola, northern Namibia and Madagascar. However, below to well below average precipitation was observed over extreme southern Liberia and Côte d Ivoire, southern Cameroon, most of Gabon, northern DRC, eastern Kenya and Tanzania, most of Mozambique, Malawi, Zambia, Zimbabwe, South Africa and western Madagascar. Details: North Africa: Observed average precipitation except over extreme northern Morocco, Algeria and Tunisia where well below average precipitation was recorded. The Sahel: Observed average precipitation. Gulf of Guinea countries: Observed average precipitation except over extreme southern Liberia, Côte d Ivoire and Cameroon where well below average precipitation was observed. Central Africa countries: Observed average and below to well below average precipitation except over central DRC where well above average precipitation was observed. GHA countries: Observed above to well above average precipitation except over eastern Kenya and Tanzania where well below average precipitation was observed. Southern Africa countries: Observed below to well below average precipitation except over parts of southern Angola and northern Namibia where above to well above average precipitation was observed. Figure 8: Cumulative Precipitation in relation to the Reference LTM %Average 1 st to 10 th December, 2015 (Source: NOAA/.NCEP/.CPC/.FEWS/.Africa/.DAILY/.AR 6
3. Outlook valid from 20 to 27 November, 2015 3.1 PRECIPITATION During the period 14 to 20 December, 2015, (Figure 10a) precipitation ranging from 10 mm to 30 mm is very likely over most of Gabon, central Congo and DRC, southern Uganda and Kenya, most of Tanzania, Botswana and South Africa, central Angola and southern Zambia. Precipitation ranging from 30mm to 50mm is likely over southern Congo, DRC, Tanzania, Malawi and Zimbabwe, northern Angola and Mozambique, central Zambia and Madagascar. Greater than or equal to 75mm precipitation is likely over southern DRC, northern Zambia and Madagascar. During the period 21 to 27 December, 2015, (Figure 10b) precipitation ranging from 10 mm to 30 mm is very likely over southern Gabon, most of Congo DRC, Tanzania, Zimbabwe, Mozambique and Botswana, central Angola, southern Uganda, Kenya, Zambia and Madagascar. Precipitation ranging from 30mm to 50mm is likely over southern Congo, DRC and Tanzania, northern Angola, Zambia and Madagascar, eastern South Africa and most of Malawi. Greater than or equal to 75mm precipitation is likely over central Zambia and Malawi. Fig10.a Precipitation forecast from 14 to 20 December, 2015 Fig10.b Precipitation forecast from 21 to 27 December, 2015 (Source: ACMAD) (Source: ACMAD) 3.2 Temperature From 14 to 22 December, 2015, neutral to positive anomalies (Figure 11) will be observed over Senegal, Gambia, Guinea Bissau, CAR, Congo, DRC, South Sudan, Kenya, Somalia, Ethiopia and Southern Africa countries. However, Gulf of Guinea and central Africa countries, eastern Ethiopia and Tanzania, most of Uganda will be dominated by neutral to negative anomalies. Fig. 11: Temperature Anomaly forecast 14 to 22 December, 2015 (Source: COLA) 7
3.3 Soil Moisture The outlook of variation on soil moisture change (Figure 12) shows an increase in soil moisture over central and eastern Africa countries, Angola, Zambia, Zimbabwe, Malawi, Mozambique, Tanzania, Kenya and Madagascar. Figure 12: Soil moisture change 14 to 22 December, 2015 (Source: COLA) 8