Global Forecasting Centre for Southern Africa
long-range forecasts for southern Africa
This is a provisional seasonal forecast produced by the Climate Systems Analysis Group (CSAG) at the University of Cape Town (www.csag.uct.ac.za). It is an ensemble mean forecast using a non-standard version of HadAM3. The forecast should be regarded as experimental. It should not be used as a substitute for the official process within the SADC region administered by the Drought Monitoring Centre in Harare; namely the pre-season production of a consensus climate outlook at SARCOF, updates to this outlook, and the refinement and interpretation of the outlook at the national level by national meteorological services. This forecast is provided as is, in a private capacity without any guarantees as to skill or error. The forecast may not be further disseminated, displayed, or publicised in any form without the permission of the seasonal forecasting team at CSAG.
Forecasts provided by CSAG
Notes: 22 February 2010The February 2010 forecast (for March-July 2010) is now available.
Select a forecast from the table below to view the images.
Forecast method:
Our forecasts are made using the United Kingdom Meteorological Office Atmospheric General Circulation Model (AGCM) HadAM3. We include the mixed phase precipitation scheme in the model integrations as this improves the model precipitation over southern Africa (see here for analysis). A ten member ensemble of the HadAM3 AGCM is integrated forward with observed (Reynolds) sea surface temperatures (SSTs). This ensures that aspects of the model (e.g. soil moisture and temperature) are in equilibrium with the model precipitation as forced by historical SSTs. The 10 model restart dumps at the end of this period are then used to start the 10 member ensemble forecast which is integrated for 6 months into the future using persisted SST anomalies. The forecast atmospheric fields are then taken as the mean of the forecast ensemble minus the mean of a 15 year climatology calculated from a 5 member ensemble hindcast (1985-1999). For precipitation the result is divided by the mean of the climatology ensemble and expressed as a percentage of normal. Other fields are expressed as an anomaly from the model climatological mean.
Our forecasts are made using the United Kingdom Meteorological Office Atmospheric General Circulation Model (AGCM) HadAM3. We include the mixed phase precipitation scheme in the model integrations as this improves the model precipitation over southern Africa (see here for analysis). A ten member ensemble of the HadAM3 AGCM is integrated forward with observed (Reynolds) sea surface temperatures (SSTs). This ensures that aspects of the model (e.g. soil moisture and temperature) are in equilibrium with the model precipitation as forced by historical SSTs. The 10 model restart dumps at the end of this period are then used to start the 10 member ensemble forecast which is integrated for 6 months into the future using persisted SST anomalies. The forecast atmospheric fields are then taken as the mean of the forecast ensemble minus the mean of a 15 year climatology calculated from a 5 member ensemble hindcast (1985-1999). For precipitation the result is divided by the mean of the climatology ensemble and expressed as a percentage of normal. Other fields are expressed as an anomaly from the model climatological mean.
