Abstract
On the evening of 23 June 2016 around 18:00 UTC, a mesoscale convective system (MCS) with hail and wind gusts passed the southern province Noord-Brabant in the Netherlands, and caused 675 millions of euros damage. This study evaluates the performance of the Weather Research and Forecasting model with three cumulus parameterisation schemes (Betts–Miller–Janjic, Grell–Freitas and Kain–Fritsch) on a grid spacing of 4 km in the ‘grey-zone’ and with explicitly resolved convection at 2 and 4 km grid spacing. The results of the five experiments are evaluated against observations of accumulated rainfall, maximum radar reflectivity, the CAPE evolution and wind speed. The results show that the Betts–Miller–Janjic scheme is activated too early and can therefore not predict any MCS over the region of interest. The Grell–Freitas and Kain–Fritsch schemes do predict an MCS, but its intensity is underestimated. With the explicit convection, the model is able to resolve the storm, though with a delay and an overestimated intensity. We also study whether spatial uncertainty in soil moisture is scaled up differently using parameterised or explicitly resolved convection. We find that the uncertainty in soil moisture distribution results in larger uncertainty in convective activity in the runs with explicit convection and the Grell–Freitas scheme, while the Kain–Fritsch and Betts–Miller–Janjic scheme clearly present a smaller variability.
Highlights
On 23 June 2016, The Netherlands was hit by a severe storm, with a storm track over the southern province of Noord-Brabant
The development of new forecasting techniques for extreme weather remains an ongoing challenge. To contribute to these innovations for The Netherlands, we investigate this grey-zone issue for this particular Mesoscale Convective System (MCS), since this study will apply a grid spacing of 4 km to the storm case in Noord-Brabant
Comparing the three cumulus parameterisation schemes (CPS) results we find Grell–Freitas ensemble scheme (GF) is closest to the results with explicit convection associated with deep clouds over the Netherlands and Belgium are not visible in the results
Summary
On 23 June 2016, The Netherlands was hit by a severe storm, with a storm track over the southern province of Noord-Brabant. The storm comprehended lightning, heavy precipitation, downbursts, and hail with a diameter of ≈10 cm [1] The storm damage has been estimated at 675 million euros. The extreme weather was a result of a Mesoscale Convective System (MCS) formed by a Spanish plume over Europe. The relatively hot dry air was advected from the Iberian Peninsula over the Pyrenees to the north, acting as a lid to the less warm but moist air underneath. The cold dry air was drawn from the Atlantic Ocean. Radio sounding observations indicated that a potentially highly unstable atmosphere was present over northern France, Belgium and the Netherlands. Surface heating during the day increased the Convective Available
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