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Development of a severe frontal rainband - plans for the Testbed-course study

Development of a severe frontal rainband - plans for the Testbed-course study. Jenni Teittinen Finnish Meteorological Institute 16 February 2007. A cold front moved over Finland on 26 August 2005. 26 August 2005 12 UTC. 27 August 2005 00 UTC. Two rainbands developed. 11.30 UTC. 12.30 UTC.

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Development of a severe frontal rainband - plans for the Testbed-course study

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  1. Development of a severe frontal rainband- plans for the Testbed-course study Jenni Teittinen Finnish Meteorological Institute 16 February 2007

  2. A cold front moved over Finland on 26 August 2005 26 August 2005 12 UTC 27 August 2005 00 UTC

  3. Two rainbands developed 11.30 UTC 12.30 UTC 13.30 UTC 14.30 UTC Severe cold frontal Pre-frontal

  4. Nature caused emergency reports on 26 August 6 reported tornadoes

  5. Lightning 26 August 2005 CG IC

  6. Motivation • Difficult to forecast – numerical models had high shear but no CAPE • How could we forecast these type quite common events? • Difficult to nowcast – we would anticipate severe weather in the first rainband • Can the Testbed-observations explain why severe weather occured in the second rainband? • The frontal rainband had line echo wave patterns –often observed with nonsupercell tornadoes • Can we observe the nonsupercell tornado development with radar reflectivity and Doppler velocity? • Can we observe a tornado vortex with the Kumpula polarimetric radar (differential reflectivity ZDR and cross-colleration coefficient)?

  7. Why severe weather occured in the second rainband? • Testbed-observations • Soundings • Wind profiler (LAP-3000) • Weather transmitters

  8. Can we observe the nonsupercell tornado development with radar reflectivity and Doppler velocity? Lee and Wilhelmson 1997b Can we observe a tornado vortex with the Kumpula polarimetric radar (differential reflectivity ZDR and cross-colleration coefficient)? Testbed data: Kumpula, Vantaa and Ikaalinen radars Ryzhkov et al. 2005

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