The TEC map related forecast algorithm takes benefit of actual trends of the TEC behaviour at each grid point. During perturbations, characterised by large TEC fluctuations or ionisation fronts, this approach may seriously fail. To avoid overestimation, the current trend information is merged with a corresponding background model of vertical TEC or corresponding median values by a weighting factor. This procedure introduces a stable climatologically TEC behaviour into the forecast estimation [Jakowski et al. 2011b].
In average, such a forecast will be better than applying the trend or model approach alone.
The presented forecasts are computed 1 hour ahead using actual trends and corresponding 27 day medians of TEC which are regularly produced as reference for current TEC estimations. The use of medians is easier because it doesn’t require separate model computations.