The ECMWF ensemble prediction system: Looking back (more than) 25 years and projecting forward 25 years. (30th September 2018)

• Record Type: Journal Article
• Authors: Palmer, Tim
• Other Names: Buizza Roberto guestEditor.; Weisheimer Antje guestEditor.
• Is Part Of: Quarterly journal of the Royal Meteorological Society. Volume 145(2019)Supplement 1
• Page Start: 12
• Page End: 24
• Publication Date: 2018-09-30
• Subjects: disaster relief reduction -- ensemble prediction -- singular vectors -- stochastic physics -- the butterfly effect; Meteorology -- Periodicals; 551.5
• DOI: 10.1002/qj.3383
• Languages: English
• ISSNs: 0035-9009

Abstract

Abstract : This paper has been written to mark 25 years of operational medium‐range ensemble forecasting. The origins of the ECMWF Ensemble Prediction System are outlined, including the development of the precursor real‐time Met Office monthly ensemble forecast system. In particular, the reasons for the development of singular vectors and stochastic physics – particular features of the ECMWF Ensemble Prediction System ‐ are discussed. The author speculates about the development and use of ensemble prediction in the next 25 years. Abstract : Although Lorenz himself developed his iconic 1963 model to show the impossibility of deterministic long‐range forecasting, it can also be used to illustrate the existence of an intermittent butterfly effect within the limit of deterministic predictability. (a) Weak growth of initial uncertainty. (b) Moderate growth of initial uncertainty. (c) Explosive growth of initial uncertainty. For users to have confidence in forecasts within this deterministic limit, it is necessary to flag situations where this intermittent explosive growth is active, and to predict plausible alternative weather scenarios probabilistically – more generally to predict flow‐dependent uncertainty. This means abandoning the deterministic paradigm that has guided the development of numerical weather prediction over many years.