African Centre Of Meteorological Application For Development Centre Africain

african centre of meteorological application for development centre africain pour les applications de la météorologie au développement

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

Ten Day Climate Watch Bulletin
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N° 1
Dekad 1st to 10th January, 2014
Straight Connector 15

1.0 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, thermal index (TI) regimes
and relative humidity.
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1.
SURFACE
1.1.1 Pressure Systems
*
The Thermal Low of 1010hPa was located at 8°N/19°E over the border
between Chad and CAR. It filled by 2hPa compared to the previous
dekad.
*
The Azores High of 1020hPa weakened by 2hPa compared to the
previous dekad. It was located at 30ºN/31ºW over North
Atlantic Ocean.
*
St. Helena High of 1020hPa weakened by 2hPa compared to the
previous dekad. It was located at 37°S/5°W over South
Atlantic Ocean.
*
Mascarene High of 1022hPa weakened by 2hPa compared to the
previous dekad. It was located at 35°S/65°E over South
Indian Ocean.

Fig. 1a: Pressure at MSL 1 to 10 Jan 2014
(source NOAA/NCEP)
2.
Inter-Tropical Discontinuity (ITD), Inter-Tropical Convergence
Zone (ITCZ) and Congo Air Boundary (CAB)
Between the 1st dekad of December (blue line) and 2nd dekad of
December (black line), 2013, the ITD migrated southward by 5 degrees
over Sierra Leone, Guinea, Cote d`Ivoire, Ghana, Togo, Benin, Nigeria,
Cameroon and CAR. It migrated southward by more than 10 degrees from
central Sudan to northern DRC. The CAB moved eastward by 2 to 4
degrees over DRC, Uganda, Tanzania and Zambia. The ITCZ moved
southward by more than 15 degrees over Indian Ocean (Figure 2).

Fig. 2: The mean position of ITD, CAB and ITCZ 2nd dekad of Dec
(black), 1st dekad of December 2013 (blue)
The red and green triangles represent their maximum and minimum
displacements respectively.
1Straight Connector 13 .2 TROPOSPHERE
1.2.1 African Monsoon
At 925hPa level (figure 3a), moderate to strong intensity of the
monsoon winds were observed over most parts of the Gulf of Guinea
(GoG) countries. The intensity of the monsoon at 850hPa which
prevailed over the GoG and most of central Africa countries was
moderate. (figure 3b).


Fig. 3a: Mean wind at 925 hPa in m/s 1 to 10 Dec
2013 (Source: NOAA/NCEP)


Fig. 3b: Mean wind at 850 hPa in m/s 1 to 10 Dec 2013,
(Source: NOAA/NCEP)
1.2.2 Dust loading particles
The map below (Figure 4a) shows low dust loading ranging from 0.1 to
0.4g/m2 over major parts Morocco, some parts of Mauritania, southern
Algeria, northern Mali and Senegal, southern Niger, much of Nigeria,
eastern Benin and western Chad. However, moderate dust loading ranging
from 0.4 to 0.8g/m2 was recorded over the border between Niger and
Chad with peaks of more than 0.8g/m2 over western Chad.
1.2.3 Dust Surface Concentration
Figure 4b shows low dust surface concentrations ranging between 5 to
50 µg/m3 over northern Morocco, Algeria, border between Algeria and
Libya, eastern Egypt, southern GoG, central Africa and East Africa
countries. Moderate concentrations (50 to 200 µg/m3) prevailed over
much of Sahel, Algeria, northern Libya, central Tunisia, northern
Benin, Togo and Ghana. The highest concentrations of 200 to 500 µg/ m3
were observed over bordering area of Mali, Niger and Algeria, eastern
Niger, northern Nigeria and western Chad with peaks of 2000 µg/m3 over
the border between Niger and Chad(figure 4b).

Fig. 4a: Dekadal Dust loading (g/m2) 1 to 10 Januanry 2014, (Source
WMO SDS-WAS: BSC-DREAM8b)

Fig. 4b : Dekadal Surface Dust Concentration (μg/m3) 1 to 10 January
2014, (Source WMO SDS-WAS: BSC-DREAM8b)
1.2.4 Thermal Index (TI) Regime
During the first dekad of January, the Thermal Index (TI) regime at
300hPa in (figure 5a) had isotherm value of 242°K over Cameroon,
Congo, DRC and Tanzania. It extended over northern Botswana, Namibia,
South Africa and Madagascar. The high TI regime ≥242°K provided
prospects for heavy rainfall.

Fig. 5a: TI at 300hPa (°k) 1 to 10 Jan 2014
(Source: NOAA/.NCEP-NCAR/.CDAS-1)
1.2.5 Relative Humidity (RH) at 850 hPa
The 850hPa level (figure 6a) had high RH value (≥60%) during the first
dekad of January over extreme south of GoG countries, Central and
Eastern Africa countries, Angola, Zambia, Mozambique, Zimbabwe,
eastern South Africa and Madagascar with peaks of 80% over Great lakes
and Central Africa countries. The remaining northern and southern
parts of the continent observed RH value ≤ 40%.

Fig. 6a: RH (%) at 850hPa 1 to 10 Jan 2014
(Source: NOAA/.NCEP-NCAR/.CDAS-1)
1.2.6 Relative Humidity (RH) at 700hPa
The 1st dekad of January had high RH value ≥ 60% at 700hPa (figure 7a)
over southern Sahel, GoG countries, Central, Eastern and some Southern
Africa countries.
The parts with threshold RH value ≥ 60% were very favorable for deep
convection that generated heavy rainfall as shown in figure 8.

Fig. 7a: RH (%) at 700hPa 1 to 10 Jan 2014
(Source: NOAA/.NCEP-NCAR/.CDAS-1)
2.0 Precipitation
Figures 8 indicate observed precipitation estimates in percentage of
normal for the 1st dekad of January 2014.
2.1 Precipitation
Well above normal precipitation was observed over Equatorial Guinea,
western Gabon, southern Tanzania and Zambia, northeast Angola,
northern Namibia, much of Zimbabwe and Zambia and southern Madagascar.
The heavy precipitation resulted from deep convection associated with
high TI regime and RH ≥ 60%. However, below to well below normal
precipitation was observed over much of Congo, parts of DRC, Angola,
northern Tanzania and South Africa.
Details:
*
North Africa: Observed normal precipitation.
*
The Sahel: Observed normal precipitation.
*
Gulf of Guinea countries: Observed normal precipitation over most
of the region.
*
Central Africa countries: observed normal to well below normal
precipitation over most of the sub-region except over Equatorial
Guinea and Gabon where well above normal precipitation was
observed.
*
GHA countries: observed normal precipitation over major part of
the region except over southern Tanzania where well below normal
precipitation was observed.
*
Southern Africa countries: Observed normal to well above normal
precipitation except over South Africa where well below normal
precipitation was observed.

Figure 8: Cumulative Precipitation in relation to the Reference in % 1
to 10 Jan 2014
(Source: NOAA/.NCEP/.CPC/.FEWS/.Africa/.DAILY/.ARC2)
3. Outlook valid for 27th December 2013 to 10th January 2014
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1.
Precipitation
During the period 27th December 2013 to 3rd January 2014, high
probability of moderate precipitation exceeding 75mm is very likely
over southern DRC, western Tanzania, most of Zambia, Malawi, Zimbabwe,
Mozambique, southeast of Angola, northern south Africa and some parts
Madagascar. From 4th to 10th January 2014, there will be persistence
of moderate precipitation exceeding 75mm over most of Zambia, Malawi,
Zimbabwe, Mozambique and Madagascar.
*
North Africa: Minimal precipitation amounts will be observed.
*
The Sahel: Minimal precipitation amounts will be observed over
this sub-region.
*
Gulf of Guinea countries: Precipitation amounts ranging from 10mm
to 20mm will be expected over extreme southern part of the region.
*
Central Africa countries: Precipitation amounts ranging from 20mm
to 150 mm will be expected over greater part of the sub-region.
*
GHA countries: Likely to observe precipitation amounts ranging
between 20mm and 100mm.
*
Southern Africa countries: precipitation amounts ranging between
20mm and 150mm are likely to prevail over this region.

Fig. 9a : Forecast of total precipitation(mm)
forecast 27 December to 3 Jan 2013-14
(Source : NCEP/GFS)

Fig.9b : Probability forecast of total precipitation exceeding 75mm,
27 December to 3 Jan 2013-14 (Source: NCEP/GFS)

Fig.9b : Probability forecast of total precipitation exceeding 75mm,
forecast 4 to 10 January 2014 (Source: NCEP/GFS)
2.
Temperature
Neutral to positive anomalies (Figure 10b) will be observed over
western part of the Sahel, eastern Ethiopia, Kenya, South Sudan, CAR,
Congo, northern DRC, Somalia, Botswana and southern South Africa.
Neutral to negative anomalies will be recorded over remaining parts of
the continent.


Fig. 10b: Temperature Anomaly forecast 30 December 2013 to 6 January,
(Source: COLA)
3.
Soil Moisture
Fig 11b shows deficit in soil moisture over most parts of the
continent except southern DRC most of Zambia, Mozambique, Zimbabwe and
Madagascar where significant increase in soil moisture will be
expected.

Fig. 11b: Soil moisture change 30 December 2013 to 6 January
(Source: COLA)
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