HRD seminar – David Richardson, ECMWF, UK – 14 March 2016

Mr. Richardson presented a seminar on the “The ECMWF Integrated Forecasting System: progress, plans and implications for tropical cyclone forecasts”.

Abstract

The European Centre for Medium-Range Weather Forecasts (ECMWF) is a world leader in the production of global weather forecasts, with a strong focus on the medium-range (up to two weeks ahead). The presentation will provide an overview of the ECMWF Integrated Forecasting System (IFS), and discuss recent and upcoming developments with a focus on model and data assimilation improvements and their impact on tropical cyclone forecasts.

Forecasting the intensity of tropical cyclones (TCs) remains a challenge for global numerical weather prediction. In the ECMWF high-resolution forecast (HRES), TCs are typically too weak in the analysis and in the early forecast ranges, although in recent years a number of cyclones have developed to become too deep later in the HRES forecast. In the lower-resolution ensemble forecast (ENS), the under-forecasting of TC intensity is characteristic throughout the forecast. Investigation of intensity errors has shown that they can originate both from the initial conditions and the model. Diagnostics of the intensity errors will be presented in the context of observation usage in the data assimilation, sensitivity to model resolution and air-sea coupling in the forecasts.  Upcoming model developments that will help to address these issues will be discussed.

In spring 2016 ECMWF will upgrade the horizontal resolution of its forecasts, to about 9 km for the HRES, 18 km for the ENS up to day 15, then 36 km for the extended range (monthly). The resolution of the data assimilation will also increase, to 9 km for the outer loop of the 4D-Var and to 18 km for the ensemble of data assimilations (EDA). The upgrade will also introduce changes to the model physics and numerics, and the data assimilation. The increase in resolution leads to improved forecasts of tropical cyclone intensity in the ENS. Initial ensemble spread is also improved for tropical cyclones by the increased resolution in the EDA. For HRES, the tropical cyclone impact of the resolution change is smaller. However, the structural representation of tropical cyclones is improved with a more clearly defined eye and better resolved rainbands.

Plans for future model upgrades will be briefly reviewed.

A recording of the presentation is available on the anonymous ftp site:

ftp://ftp.aoml.noaa.gov/pub/hrd/blog/seminars/2016/Richardson_HRD_Seminar_20160314.mp4

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