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Extreme convection effects

Ensemble Control Forecast tends to over-forecast extreme convection, especially in the maritime tropics.  Forecast rapid vertical motion can result in spurious quasi-circular waves (sometimes rings) in convective precipitation fields. These gravity waves gradually spread outwards.  They can even move well upwind, giving a false impression of an eastward-moving trough.  The source of these false features should be identified and the effects discarded from forecasts.  Changes to the IFS moist physics in 2019 have reduced but not entirely removed this effect. 

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Fig9.6.6-5: The IFS ENS and AIFS ENS ensemble forecasts of 9 July at 12 UTC shows the convection was extremely unpredictable in both systems. IFS ENS showed a moderate probability of rain over Burkina Faso but AIFS ENS correctly forecast predominantly dry conditions.  This is only one example which may or may not be typical of a bias.   But overall, the physically-based IFS and ML-based forecasting systems were struggling to handle convection and the passage of tropical waves over Sahel.

(FUG Associated associated with Cy50r1)