Introduction
Two cases (US Tornado case and Africa case) - different types of convection
US Tornado convection case (Arkansas)
On the 27 April 7pm local time (00UTC 28 April), tornadoes hit towns north and west of Little Rock, Arkansas killing approx 17 people. (http://edition.cnn.com/2014/04/28/us/severe-weather/index.html?hpt=hp_c2). On the evening on the 28 April fatal tornadoes occurred over Mississippi (http://www.bbc.co.uk/news/world-us-canada-27199071).
African diurnal deep convection (Central Africa)
Initial conditions
Sensitivity experiments
Impact of the improved diurnal cycle of convection
Namelist block NAMCUMF, parameter RCAPDCYCL
RCAPDCYCL = 2 (default) activates the diurnal cycle using sub-cloud CAPE,
RCAPDCYCL = 1 diurnal cycle using surface sensible heat flux,
RCAPDCYCL = 0 reverts the code to a setting before the diurnal cycle for convection was
implemented.
Look at the timing of convective and precipitation events.
Optimization factor for the time scale adjustment:
Namelist block NAMCUMF, parameter RTAUA
RTAUA=1. default value (set it to 0.33 and 3.)
The ratio between the actual cloud base mass flux and the unit (initial) cloud base mass flux:
Look at the amplitude of precipitation.
Further reading
201404 - Convection - Arkansas U.S
Comments
The forecasting system at ECMWF makes use of "ensembles" of forecasts to account for errors in the initial state. In reality, the forecast depends on the initial state in a much more complex way than just the model resolution or starting date. At ECMWF many initial states are created for the same starting time by use of "singular vectors" and "ensemble data assimilation" techniques which change the vertical structure of the initial perturbations.
As further reading and an extension of this case study, research how these methods work.
Acknowledgements