New ensemble-based forecast guidance products

Anders Persson

SMHI, Sweden


This seminar will explore different forms of presenting ensemble forecast output to forecsters, in ways they prefer to work with it. Following the tradition of the Bergen School, the use of "composite maps"is suggested where various probability information is displayed against a background of ensemble mean flow. Up to 3-4 day lead time the maps appear like standard synoptic charts while at longer lead time, due to the filtering effect of taking an ensemble mean, the flow assumes a more large scale appearance. Time permitting, issues related to numerical weather and ensemble forecasting will also be discussed, including the desired spatio-temporal variability, and bias correction of NWP forecasts.