Warren works in the Ensemble Forecasting Group with particular interest in understanding and estimating model forecast error.
Areas of expertise:
Warren is a senior scientist working on stochastic physics in the Met Office Ensemble Prediction System MOGREPS. Accurate estimates of forecast uncertainty are important products of an ensemble system. This is taken from the ensemble spread which is generated through initial condition perturbations and stochastic elements included within the model that increase the rate of growth of spread within the ensemble.
The current focus of Warren's work into stochastic physics is a Stochastic Kinetic Energy Backscatter scheme (SKEB2). This scheme injects wind increments into the model at every timestep based on a random streamfunction forcing pattern that is modulated by locally diagnosed energy dissipation fields. In this way the model forecasts are forced to diverge more rapidly in regions where there is a perceived drain of energy from the model.
Warren is currently responsible for maintaining the forecast model components that feed into the operational MOGREPS system. This includes implementing new developments like SKEB2 and testing other changes to the system (like resolution).
Warren joined the Met Office in 2008 after having worked at the South African Weather Service since 1993. He was involved in Numerical Weather Prediction (NWP) for most of that time and was responsible for implementing and maintaining various modelling systems including the COLA T30 GCM, NCEP T126 GFS, NCEP Eta and Met Office UM (regional 12km and 4km). He also developed a forecast verification system and managed the NWP group for several years.
Warren completed his PhD at the University of Cape Town in 2002. This work involved a new approach to understanding large-scale atmospheric variability on a seasonal time-scale through atmospheric energetics.
Warren was a member of the (THORPEX) GIFS-TIGGE working group from its inception in 2005 until 2008 and he helped introduce the successful concept of local forecast processing centres into the plan of a Global Interactive Forecast System (GIFS). This has been a big step forward in transferring NWP output from global producing centres into products with local value.