Christoph Gatzen - Derechos in Central Europe
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Transcript of Christoph Gatzen - Derechos in Central Europe
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2010/07/12 1500 UTC
Gust 25+m/s Tor Hail 2+ cm
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Helgoland, 2010/07/12 1330 UTC
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Derecho-definition Major axis length: 400 km Fujita, T. T., and R. W. Wakimoto, 1981
Fig. SPC web site (Johns, Evans, and Corfidi)
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Derecho climatology
Fig. SPC web site (Johns, Evans, and Corfidi)
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Gatzen, C., 2004: A Derecho in Europe: Berlin, 10 July 2002. Wea. Forecasting, 19, 639–645
Punkka, A.-J., J. Teittinen, R. H. Johns, 2006: Synoptic and Mesoscale Analysis of a High-Latitude Derecho–Severe Thunderstorm Outbreak in Finland on 5 July 2002. Wea. Forecasting, 21, 752–763
López , J. M., 2007: A Mediterranean derecho: Catalonia (Spain), 17th August 2003. Atmos. Res., 83, 2-4, 272-283
Gatzen, C., T. Púčik, D. Ryva, 2011: Two cold-season derechoes in Europe. Atmos. Res., 100, 4, 740-748
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Germany, 1997-2011: 10 new Derechoes, Average path 730 km Possibly 7 further events 106 Fatal, 200 INJ
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Derecho hazards
• Outdoor activities • Traffic • Electrical outages • Large tree blow downs
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Radar view
Reflectivity
Relative Velocity
Fig. Przybylinski, 2000
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Conceptual model
Fig. Mahoney, Lackman, and Parker, 2009
Fig. Fujita, 1978
Cold pool
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Increasing cold pool speed
Fig. Mahoney, Lackman, and Parker, 2009
PGA: Pressure gradient acceleration VAu’, VAv’: Vertical advection of perturbation wind VAū: Vertical advection of environmental flow
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Idealized model studies
Fig. Weisman 1993
Rotunno, Klemp, Weisman, 1988 (RKW theory): Balance of cold pool and shear circulations
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RKW and storm environments
Fig. Evans and Doswell, 2001
• RKW is not confirmed by proximity soundings
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Observational studies Derecho environments are characterized by
• High low-level moisture (almost always) Johns and Hirt, 1987 Johns, Howard, and Maddox, 1990 Burke and Schultz, 2004 Coniglio, Stensrud, and Richman, 2004
• Steep lapse rates (often) Johns and Hirt, 1987 Johns, Howard, and Maddox, 1990 Cohen, Coniglio, S. F. Corfidi, and S. J. Corfidi, 2007
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Observational studies Derecho environments are characterized by
• 250 hPa divergence (almost always) Johns and Hirt, 1987 Johns, Howard, and Maddox, 1990 Coniglio, Stensrud, and Richman, 2004
• Strongly-forced at 500 hPa (often) Evans and Doswell, 2001 Johns, Howard, and Maddox, 1990 Burke and Schultz, 2004
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Observational studies Derecho environments are characterized by
• Strong low-level WAA (always) Johns and Hirt, 1987 Johns, Howard, and Maddox, 1990 Burke and Schultz, 2004 Coniglio, Stensrud, and Richman, 2004
• A strong low-level jet (almost always) Johns and Hirt, 1987 Johns, Howard, and Maddox, 1990
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Example: 500 hPa flow and derecho path
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Example: 500 hPa flow and derecho path