February 2010

Strengthening Weather Forecasting worldwide


Operational weather forecasting by WMO Members is the focus of its Global Data-Processing and Forecasting System (GDPFS). This system spans the day-to-day around-the-clock work of teams of weather forecasters, computing specialists, technical and support staff of the National Meteorological and Hydrological Services (NMHSs) of the 189 WMO Members. Many forecasting centres carry out numerical weather prediction (NWP) activities, which involve the running of complex mathematical simulation models of the atmosphere to describe both the current state of the atmosphere and make predictions of its future states from hours to months to seasons in advance.

The activities of the GDPFS are part of the World Weather Watch Programme, which is the responsibility of the Commission for Basic System (CBS). Following its fourteenth session (25 March to 2 April 2009, Dubrovnik, Croatia), CBS, within its Open Programme Area Group of Data-Processing and Forecasting System, held several follow-up meetings to enhance its activities in operational forecasting.

Ensemble prediction systems

The meeting of the CBS Expert Team on Ensemble Prediction Systems (EPS) was held at the UK Met Office from 5 to 9 October, 2009. Significant progress has occurred in operational EPS, including in resolution, ensemble size, length of integration and frequency of forecast cycles. The horizontal resolution has increased from about 90 to 110 kilometres to 50 to 70 kilometres for most global system, while the European Centre for Medium-Range Weather Forecasts ( ECMWF) is working towards 30 kilometres. The number of vertical levels is also increasing, and many centres have increased ensemble size, with the length of integration extending to 10 to 15 days at most centres. Higher resolution regional EPS and those that focus on specific high-impact phenomena, post-processing products and multi-centre ensembles continue to develop.

Liaison with the research activities is well established through THORPES/TIGGE, which is exploring the concept of grand global ensemble methods, including in the development and planning of a Global Interactive Forecast System, which could provide new products for operational use.

However, many NMHSs, especially those of developing countries, do not have the computing facilities or capability to generate products from ensemble fields. The application of EPS to predict severe or high-impact weather events is critical, and the Expert Team discussed the associated challenges and guidance on how to promote and enhance use of EPS in routine forecasting, for use by trainers and forecasters.

Forecast verification

The meeting of the CBS Coordination Group on Forecast Verification (CG-FV) was held at ECMWF in Reading, United Kingdom from 24 to 26 November, 2009. The Group reviewed the existing standard for NWP deterministic verification as defined in the WMO Manual on the GDPFS. Performing NWP without verification is inconsistent with quality management principles, does not provide necessary quality information to forecasters, and would result in an unreliable and unsustainable activity. The Coordination Group agreed that some essential parts of the recommended actions for verification should be made mandatory and that efficient and systematic verification systems should be run in real-time.

The meeting recommended that the present focus of its work should be on updating the verification of upper air fields. However, CG-FV would in the future also examine the verification of surface parameters and developed a proposal for an updated standard verification system. The group will maintain links with research in development of verification scores, especially for surface weather parameters. Additionally, following a CBS request, the meeting developed a list of functions expected from a Lead Centre for Deterministic NWP Verification.

Severe Weather Forecasting Demonstration Project

All of this work underpins recent advances in the Severe Weather Forecasting Demonstration Project (SWFDP) in southern Africa and the South Pacific Islands. In 2009, SWFDP made two major advances: expansion of the regional project to include all 16 countries of southern Africa, and the launching of a new regional project for the South Pacific Islands, first in a pilot phase that includes four Island States (Fiji, Samoa, Solomon Islands, Vanuatu), as well as GDPFS Centres of the Met Office (UK), Honolulu and NCEP (USA), ECMWF, Wellington (New Zealand), Darwin (Australia), Nadi (Fiji), and Météo-France.

In conjunction with these initiatives, important training activities provided weather forecasters worldwide with technical knowledge and practical guidance related to use of advanced NWP products, including from EPS, in severe weather forecasting – all in collaboration with the Public Weather Services programme training on delivery of warning services. SWFDP is a vital mechanism for increasing the reach and effectiveness of the GDPFS, especially for developing countries.



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