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Analysis of May 13th, 2015 Tornado Event at Gerbépal (France)

This study analyzes the May 13th, 2015 tornado outbreak in Gerbépal, France using radar, lightning, and NWP model data. The analysis focuses on severe convective parameters, supercell features, radar reflectivity, and lightning activity. The study provides insights into the clues prior to and during the tornado event.

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Analysis of May 13th, 2015 Tornado Event at Gerbépal (France)

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  1. Analysis of May 13th 2015 tornado event at Gerbépal (France) using radar, lightning and NWP model data Tony Le Bastard1, M. Kreitz1, S. Baille2, D. Prévot3 Météo France, 1Toulouse, 2Aix-en-Provence and 3Villeuneuve d'Asq September 20, 2017 9th European Conference on Severe Storms, Pula, Croatia

  2. Outline 1. Introduction 2. Analysis - NWP model - Radar - Lightning 3. Conclusion Météo-France

  3. Outline 1. Introduction 2. Analysis - NWP model - Radar - Lightning 3. Conclusion Météo-France

  4. Météo-France Tornado of Gerbépal – 13/05/2015 — 04 Introduction May 13th, 2015 Tornado outbreak over NE France (1 EF2) and S Germany (1 EF1, 1 EF2, 2 EF3) Focus on the supercell that produced: - an EF2 tornado at Gerbépal around 17h55 UTC (19h55 loc.) - large hailstones (~ 5cm)

  5. Tornado (Gerbépal) C-band Doppler radars : Single-pol. (Nancy) 1 2 100 km radius from radar Introduction Dual-pol. (Montancy) Météo-France Tornado of Gerbépal – 13/05/2015 — 05

  6. Objective What were the clues prior to and during this event? Météo-France Tornado of Gerbépal – 13/05/2015 — 06

  7. Outline 1. Introduction 2. Analysis - NWP model - Radar - Lightning 3. Conclusion Météo-France

  8. Analysis NWP model: severe convective parameters Model: AROME (init. 13/052017 06UTC) Evaluation: poster P13 by Marie Boisserie on Thursday 2:30 pm Météo-France Tornado of Gerbépal – 13/05/2015 — 08

  9. Analysis NWP model Model: AROME (init. 13/052017 03UTC) Reflectivity 850 hPa at 18UTC Météo-France Tornado of Gerbépal – 13/05/2015 — 09

  10. Analysis NWP model Refl. 850 hPa (shaded), 10m wind and vert. vel. 700 hPa (iso) Adapted from Lemon and Doswell 1979 AROME horizontal res.: 2.5km Météo-France Tornado of Gerbépal – 13/05/2015 — 010

  11. Analysis NWP model Refl. 850 hPa (shaded), 10m wind and vert. vel. 700 hPa (iso) Adapted from Lemon and Doswell 1979 Supercell features AROME horizontal res.: 2.5km Météo-France Tornado of Gerbépal – 13/05/2015 — 011

  12. Outline 1. Introduction 2. Analysis - NWP model - Radar - Lightning 3. Conclusion Météo-France

  13. Analysis Radar: reflectivity L: Left mover R: Right mover T: Tornado Storm initiation ~ 16 UTC Météo-France Tornado of Gerbépal – 13/05/2015 — 013

  14. Analysis Radar: reflectivity Reflectivity Montancy 0.7° Deep-layer flow Left mover 2 T Right mover 2 dBZ Météo-France Tornado of Gerbépal – 13/05/2015 — 014

  15. Analysis Radar: Storm Relative Velocity (SRV) 3 or 4 cyclonic mesocyclones (+1 or 2 anticyclonic) highlighted by the Storm Relative Velocity Well defined mesocyclone on supercell 2R more than 45 min before tornadogenesis Météo-France Tornado of Gerbépal – 13/05/2015 — 015

  16. Ø (cm) 0.5 Hail 2.0 Rain Analysis HYDRE HYDRE: Precipitation type diagnosis (radar + satellite + NWP model + surface obs.) HYDRE from 16 to 19 UTC Météo-France Tornado of Gerbépal – 13/05/2015 — 016

  17. Differential reflectivityZdr = Zhh – Zvv = f (mean axis ratio) Analysis Radar: Zdr Low Zdr (~ 0) :Drizzle, small drops,dry snow / graupel / hail High Zdr (> 1) :Large drops Column ofhigh Zdr = Supercooledliquid drops = Strong updraft Météo-France Tornado of Gerbépal – 13/05/2015 — 017

  18. Analysis Radar: Zdr 0°C 0°C 0°C Météo-France Tornado of Gerbépal – 13/05/2015 — 018

  19. Analysis Radar: Zdr Zdr Montancy 2.2° 13/05/2015 from 1730 to 1805 UTC dB 0°C Decrease of Zdr column heightRelated to tornadogenesis? (Picca et al. 2015) Météo-France Tornado of Gerbépal – 13/05/2015 — 019

  20. Outline 1. Introduction 2. Analysis - NWP model - Radar - Lightning 3. Conclusion Météo-France

  21. Analysis Lightning Reflectivity and lightning 13/05/2015 from 1630 to 1830 UTC Météo-France Tornado of Gerbépal – 13/05/2015 — 021

  22. Analysis Lightning Lightning activity of the tornadic supercell Météo-France Tornado of Gerbépal – 13/05/2015 — 022

  23. Analysis Lightning Lightning activity of the tornadic supercell Météo-France Tornado of Gerbépal – 13/05/2015 — 023

  24. Outline 1. Introduction 2. Analysis - NWP model - Radar - Lightning 3. Conclusion Météo-France

  25. Conclusion The French operational NWP model AROME and in-situ observations provided clues for the formation of a severe convective and tornadic event Before storm initiation: - Extreme values of SCP and STP - Supercell structure on NWP fields When storms were ongoing: - Textbook supercells signatures on radar (reflectivity and SRV) - Significant hail cores in HYDRE - Zdr columns revealing strong updrafts • - Lightning jumps before tornadogenesis Future works: • - Deeper analysis (satellite, surface obs...) • - Automatic detection of mesocyclones, lightning jumps and Zdr colums Météo-France Tornado of Gerbépal – 13/05/2015 — 025

  26. Thank you! Photo: tornado in the very far west of France (May 21, 2016) Contact: tony.lebastard@meteo.fr

  27. 500 hPa Geopot., wind and temp. 850 hPa wet bulb temp and SLP L 1010 Analysis NWP model Model: ARPEGE (init. 13/052017 00UTC) Low-level humidity, surface low Small upper trough, mid-level jet Météo-France Tornado of Gerbépal – 13/05/2015 — 027

  28. Analysis NWP model: vertical profile CAPE ~ 1300 J.kg-1 SRH ~ 300 m².s2 Environment conducive for supercells Météo-France Tornado of Gerbépal – 13/05/2015 — 028

  29. Analysis Radar: Storm Relative Velocity (SRV) New circulation ? 17h09 17h14 17h19 17h24 17h29 Strenghthening Tornado 17h49 17h34 17h39 17h44 17h54 Météo-France Tornado of Gerbépal – 13/05/2015 — 029

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