Parametric descriptions of the boundary layer winds in tropical cyclones have proven extremely valuable since they were initially proposed some 50 years ago. The relative simplicity of parametric methods enables a range of engineering and climatological studies that could not be accomplished using the more sophisticated numerical models that have evolved. Typical of the applications for such parametric models have been idealisation of structure and behaviour for forecasting, hindcasting, initialisation of numerical models, statistical modelling and public education. Parametric models also provide the spatial and temporal surface forcing for incorporation into a variety of "downstream" engineering design, numerical modelling and risk assessment studies such as: offshore facilities design; wind, wave, continental shelf current and storm surge design criteria; onshore infrastructure design (eg ports, public housing, wind sensitive structures); public evacuation and disaster planning (wind and storm surge) and insurance risk assessment.
While a range of parametric model developments have occurred, there remains no consensus as to the best representations which should be used. This has been complicated by the many features which it might be expected that a comprehensive parametric model should address and some concentration on specific rather than general requirements. The need for an updated parametric model to support these studies was emphasised by the WMO/CAS Fourth International Workshop on Tropical Cyclones (IWTC-IV) in April 1998. It was recommended that there would be considerable benefit from development of a single, comprehensive, benchmark parametric wind and pressure field model of tropical cyclones. This model would provide: a common reference point for other methods; well-documented error and parameter sensitivity ranges; a framework for adding additional features; a systematic facility for storm parameter identification and classification; and a means of reducing potential confusion between various alternative modelling approaches.
There now exist many opportunities to gather together a more comprehensive parameterised description of tropical cyclones than has been attempted to date. For example, much more data are now available and numerical models have the degree of resolution and sophisticated physics to be used in parametric developments. In addition to improved structure definition, an updated parametric model will need to include capabilities which could represent transient surface wind features and life-cycle storm structural changes. A multi-faceted model which addresses aspects of near-surface wind and pressure profiles both before, during and after landfall is now feasible and could be used to form a new standardised reference. This paper reports on progress towards such an outcome