Tornado in ern France on 11th February - short reanalysis

Hi,

last Sunday, Feb 11th, a strong tornado hit the french village of Soulosse-sous-saint-Elophe during the late afternoon hours. Another one hit the town of Eqeurdreville near Cherbourd in Normandy, pretty close to the coast. These two tornadoes were part of a small severe weather event which took place over nrn and nern parts of France in the range of two small but potent upper-level-short-wave troughs.

Following is a link to a short video of the damage caused by the 1st tornado near Cherbourg:

http://www.meteo-normandie.fr/Evenement-Equeurdreville,311.html

and here are a few damage pictures from Soulosse, the village that got hit later in the day.

23777130220071700.jpg


http://www.m6.fr/cms/display.jsp?id=p2_541431

I hope this last link works since it is a gallery embedded within a website. According to the media, 8 persons have been injured, two of which severely. About 2600 inhabitants were cut-off from electricity in the hours after the storm struck.

http://essl.org/cgi-bin/eswd.cgi

The reports that were received on the ESSL database that day are still online.

The wx pattern that lead to these tornadic storms seems to be pretty typical of winter severe cases in many parts of wrn and ctrl Europe. Dynamics were very strong with lots of DL shear and LL shear, though directional shear was rather low. It could have been enhanced by local topography, since the town lies in rather hilly terrain west of the Vosges mountains.

For an enhanced risk of wintertime storms, one needs to be in the range of slightly warmer, marine airmasses with plenty of cold air aloft. That was the case on Feb 11th since atlantic air (mPw) was moving in behind an occluded front in the swrn quadrant of a strong sfc low centered near the British Isles.

The eastern parts of France were in a favorable area for strong lift as a strong UL jet streak progressed slowly ese and the region of concern was placed under the left-exit region. The colors represent the wind speeds in knots.

2007021112_38.gif


Looking at the soundings, it can be seen that there was not much instability to deal with, at least by typical Great Plains standards. The Nancy 12Z profile reveals only slightly more than 300 J/kg but there´s nearly no CIN and an adiabatic profile in the PBL as well as very cold air aloft. LCL and LFC are colocated.

2007021112.07180.skewt.gif

The sounding of Trappes, located sw of Paris looks even more favorable shear-wise for some low-topped supercell convection if storms would develop.

2007021112.07145.skewt.gif


I´ve re-analyzed these two profiles with RAOB 5.7 and it gave a SRH0-3km value of about 150 m^2/s^2 and 59 m^2/s^2 for SRH0-1km, marginally sufficient for rotating updrafts. The LL CAPE values though were pretty siginficant with about 103 J/kg which is nearly 1/3 of the total available CAPE confined to the lowest 3 km. Trappes has impressive kinetic values which are not seen that often in ctrl European environments when sufficient instability is co-located. SRH0-3 is 421 m^2/s^2 and SRH0-1 193m^2/s^2, indicating a very favorable environment for rotating storms and supercellular tornadoes, the more so as LL CAPE was about 125 J/kg, positively impacting low-level parcel acceleration and stretching beneatch updrafts. The profiles look somewhat similar to some of the soundings presented in a paper by Jon Davies about Cold-Core-tornadoes (http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175/WAF967.1), though the sysnoptic-scale environments are probably very different. I think we don´t have typical settings with a dryline and intersections of warm-sector air and sfc thermal heat ridges, at least not in our winter setups (like depicted in Davies´ paper http://members.cox.net/jondavies6/WAF Dec 06/pg 10.jpg) but there could be some warming in the areas of subsidence between the smaller vort maxes in the range of the trough. That could take over the role of one, bigger heating axis. Essential seems to be a combination of very cold UL air with some "warmed up"-maritime air which becomes well-mixed over land surfaces, combined with strong dynamics and wind shear. So one could speculate that this sort of environment could be some sort of hybrid of the "typical" sern States winter environment and cold-core storms...(?)

Best regards,
Lars
 
ESWD query

Hi,

I´ve noticed that since yesterday evening, you have to look up the data for the events on 11th February in the database on the ESWD website. It is no longer shown via the link I´ve posted above. Sorry for that...

Lars
 
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