An investigation of the tipping term as a prognostic tool in short-range thunderstorm forecasting.

Sleigh, MW; Collier, CG

Abstract

A UK Met Office nowcasting system – GANDOLF – was operated by the Met Office and the University of Salford during the Sydney 2000 Forecast Demonstration Project. The purpose of this project was to test and evaluate the current state-of-the-art in nowcasting technology, and initial verification by the University of Salford has shown GANDOLF’s performance to be poor. The system uses a conceptual model of the life cycle of an idealised convective cell to forecast the evolution of radar-observed storms in an object-oriented fashion. Analysis has shown the implementation of the model to be flawed - particularly in that it relies on relatively low resolution NWP model forecasts - rather than the use of conceptual modelling itself. The advent of very high resolution 3D wind fields produced by 4DVAR modelling techniques offers a way of circumventing many of the problems inherent in GANDOLF, and such data have been obtained for the cases during which GANDOLF was operational. These were produced by the National Center for Atmospheric Research’s VDRAS system, which was also operated during the FDP as part of the Autonowcaster system. The wind data allowed the calculation of time series of the 3D tipping term field, which, it has been theorised, can be used as a prognostic tool in automated convection nowcasting. This paper summarises the theory of the tipping term, and presents the methodologies and results of a number of tests performed on the tipping term data. The conclusions of these tests indicate that the theory of the tipping term is valid, and that the tipping term does have predictive capabilities. Potential uses of the tipping term include automatically distinguishing between stratiform and convective systems, classifying convective systems by shape, determining the stage of development of observed storms and guiding their evolution forecasts within a concpetual model, forecasting the time of peak reflectivity, and identifying and forecasting mesocyclones

Citation

Sleigh, M., & Collier, C. (2004). An investigation of the tipping term as a prognostic tool in short-range thunderstorm forecasting. Atmospheric Research, 69(3-4), 185-198. https://doi.org/10.1016/j.atmosres.2003.09.003

• Journal Article Type: Article
• Publication Date: Feb 12, 2004
• Deposit Date: Sep 24, 2007
• Journal: Atmospheric Research
• Print ISSN: 0169-8095
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 69
• Issue: 3-4
• Pages: 185-198
• DOI: https://doi.org/10.1016/j.atmosres.2003.09.003
• Publisher URL: http://dx.doi.org/10.1016/j.atmosres.2003.09.003