European Storm Forecast Experiment

Mesoscale Discussion

Mesoscale Discussion
Valid: Mon 09 Jun 2014 20:00 to Mon 09 Jun 2014 23:00 UTC
Issued: Mon 09 Jun 2014 20:02
Forecaster: GROENEMEIJER / PUCIK

An ongoing bow echo with a history of producing extreme severe wind gusts (>32 m/s) and likely an embedded supercell structure continues to move NEward across W Germany. 10-15 m/s low-level shear ahead of the system and low LCL heights suggest that the system will continue to harbour a risk of embedded - possibly strong - tornadoes in addition to the severe wind threat. The system will likely continue for at least several hours as the airmass ahead remains very unstable per sfc obs and NWP guidance. Mesoscale Discussion

Mesoscale Discussion
Valid: Mon 09 Jun 2014 19:00 to Mon 09 Jun 2014 22:00 UTC
Issued: Mon 09 Jun 2014 19:33
Forecaster: PUCIK / GROENEMEIJER

Convective storms are intensifying across NW and N France. Their environment is characterized by strong 25-30 m/s deep-layer (0-6 km) shear and about 500-1500 J/kg CAPE, the highest values in the southeast of the area.

Per numerical guidance and observed N to NE surface winds, these storms will experience a strongly helical low-level flow across far northern France and Belgium. There, LCL heights are very low with T/Td spreads typically around 2-4 degrees C. This suggests that tornadoes will be possible with the best organized storms in northern France and Belgium. Some large hail and severe winds will probably occur as well. The threat for large hail is highest in the south of the MD area, where the lapse rates are the steepest.