Wednesday, 9 November 2016
Broadway Rooms (Hilton Portland )
The tornado outbreak of 24-25 June 1967 led to eight confirmed tornadoes throughout France, Belgium and the Netherlands, including tornadoes rated F4 and F5. The WRF model is used to simulate the mesoscale environments and the resulting tornadoes at grid spacings of 60 km, 20 km, 4 km and 800 m initializing from the ECMWF ERA-20C reanalysis. Model results demonstrate a high CAPE and shear environment in the areas of tornadic development on 24 June, with CAPE values exceeding 3000 J/kg. The storms of 24 June display supercellular characteristics in Northern France and Belgium from 1700-2000 UTC, which is the time of reported tornadic damage. On 25 June model results show slightly less intense convection relating to a lower CAPE and shear environment with CAPE values up to 1500 J/kg. Swaths of extreme wind speed from the 800m grid are compared to the actual tornado tracks recorded. The overall storm morphology is compared to similarly damaging events in the United States. This simulation demonstrates the utility of the ERA-20C for use as initial and boundary conditions for historical severe weather events throughout Europe as well as the ability of the WRF model to provide physically plausible reconstructions of significant storms at very fine grid spacing for observation-poor past events.
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