Tailoring Ensemble Output to Meet Forecasters' Needs - Some Highlights from the Met Office and ECMWF

Tim Hewson
UK Met Office

Abstract:

One of the biggest challenges facing forecasters nowadays is managing, in real-time, increasingly large volumes of data. Across most lead times ensembles now provide the majority of this data. It is therefore incumbent upon modelling centres to devise ingenious ways of converting their ensemble data into a highly compressed product format that is carefully tailored to meet forecaster's needs.

This talk will focus on two relatively new classes of product that fulfil the above requirement. The first class, instigated at ECMWF, is known as the 'extreme forecast index' or EFI. This aims to provide a summary measure, for anywhere in the world, of the likelihood of specific weather parameters reaching thresholds that are climatologically extreme. One related product provides, on a single global chart, a snapshot of where anomalous weather of many types will likely occur on a given day. The second class of product, developed at the Met Office and since ported to ECMWF, has the generic term 'cyclone database'. This facility applies algorithms for identifying and tracking fronts and cyclonic features to ensemble runs, and then, through intelligent graphical post-processing, makes the connection between synoptic scale features and adverse weather. One particular attraction is the ability to see the degree to which the deterministic run represents a mid-range solution in terms of synoptic feature handling.

The talk will also touch on how the above products are used operationally at the Met Office, and will also briefly highlight Met Office plans for structuring its operational output in future. This includes the introduction of a very high resolution ensemble over the UK.