The predictability of storm tracks
Froude, Lizzie S. R.
PublisherUniversity of Reading
MetadataShow full item record
Extratropical cyclones are important to the day to day weather of the midlatitudes. They provide essential rainfall for human activities such as agriculture, but can also cause large amounts of damage by their strong winds and heavy precipitation. It is therefore very important to predict these cyclones as accurately and as far in advance as possible. A new storm tracking approach to forecast verification is developed and implemented to obtain detailed information about the prediction and predictability of storms. The approach is applied to observing system forecast experiments constructed using the European Centre for Medium Range Weather Forecasts (ECMWF) 40-year reanalysis system (ERA40). It is also used to analyse the ECMWF and National Centers for Environmental Prediction (NCEP) Ensemble Prediction Systems (EPS). An Internet Service ha" been developed to allow users to run a storm tracking program from a web browser with remote datasets and distributed computing. The service has been used in this thesis to help with the large amounts of data processing involved. Results show that the intensity and propagatiun speed of storms are more difficult to predict than the direction the storms take. There is a small bias for forecast cyclones to propagate too slowly. The importance of a high vertical resolution of observations is highlighted. This is particularly true for northern hemisphere winter storms, which have much larger growth rates. It is shown that the ECMWF EPS has a slightly higher level of performance than the NCEP EPS in terms of the prediction of storms. The results also illustrate a number of benefits an ensemble forecast can offer over a single deterministic forecast. It is suggested that in the future operational forecast centres should consider using a storm tracking verification approach in addition to the standard approaches.