Improving Prediction of Fronts

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Once a weathermodel has been initialised from our best estimate of the current stateof the atmosphere, it will diverge from the real state of theatmosphere over time. The period of time during which a singledeterministic weather model provides useful information is known asthe "useful forecast range'', which provides a measure of thepredictive skill of the model. For example, the ECMWF useful forecastrange is now typically between 7 and 10 days. Extending the useful forecast range of weatherforecasts (and improving accuracy over that range) would have clearbenefits to society and the economy; benefits include: energy management, protection ofinfrastructure, coordinating disaster response, agricultural planning,planning in travel and leisure industries, transportation management,targeting of weather-sensitive health conditions, water resourcemanagement, improved decision making in commodity markets,environmental decision making and natural resource management. In thisproject, we will develop a means of understanding of some currentlimitations to predictive skill and the useful forecast range, andwill investigate practical methodologies for removing them. This is ofcourse a huge topic; we shall restrict our investigation to the drydynamical core (the part of the model that predicts winds, temperatures and pressures), and concentrate on one important phenomena, namely theevolution of fronts and, in particular, the resulting feedback on the large scale atmospheric circulation. Fronts play a key role in the delivery ofprecipitation, and many severe weather events, which have an importantrole in all of the socioeconomic areas discussed above. The challenge associated with fronts is that although the distance from one side of a weather frontto another is very small compared to the distance between two grid points inan operational forecast model, fronts have a significant impact on the wind speedand direction as well as the pressure over a large region around the front. The aim of this projectis to find improvements in dynamical core design that can improve the predictionof the winds and pressures in the vicinity of fronts.