An external view of the Met Office building at night.

Dr Warren Tennant

Areas of expertise

  • Ensemble prediction
  • Numerical modelling systems
  • Stochastic parameterization
  • Forecast uncertainty
  • Forecast verification

Publications by Warren

Current activities

Current activities Warren is a scientific manager of the Global Numerical Weather Prediction Group. The primary responsibility of this group is to understand the main components of the global numerical weather prediction system and to drive the implementation of scientific advances into operations in an expedient and sustainable way. This includes providing evaluation and diagnostic tools for assessing changes to the NWP system, with a focus on defining appropriate testing criteria tailored to the type of change being made.

Recent work on ensemble methods has seen Warren playing a key role in the project to replace the Ensemble Kalman Transform Filter (ETKF) with an Ensemble of 4D-Ensemble-Var (En-4DEnVar) scheme in the Met Office Ensemble Prediction System (MOGREPS). This new scheme includes enhancements to the treatment of model error, which is important in controlling ensemble dispersion such that probability forecasts remain reliable at all forecast lead-times. In addition to SPPT and SKEB, we use an Additive Inflation scheme that randomly samples historical analysis increments from the same season in previous years, to act as a proxy for model error, and apply scaled forms of these increments during the ensemble forecast.

Career background

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. More recently, until December 2013, he was a member of the EUMETNET Short-Range Numerical Weather Prediction Expert Team on Ensemble Prediction Systems, which addresses predictability issues and uncertainties in the NWP models, LAMEPS and ensemble data assimilation.