Transcript Development of a severe frontal rainband - plans for the Testbedcourse study Jenni Teittinen Finnish Meteorological Institute 16 February 2007

Development of a severe
frontal rainband
- plans for the Testbedcourse 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
13.30 UTC
14.30 UTC
Severe cold
frontal
Pre-frontal
Nature caused emergency reports on 26 August
6 reported
tornadoes
Lightning 26 August 2005
CG
IC
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)?
Why severe weather occured in the second rainband?
• Testbed-observations
• Soundings
• Wind profiler (LAP-3000)
• Weather transmitters
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 crosscolleration coefficient)?
Testbed data: Kumpula, Vantaa and Ikaalinen radars
Ryzhkov et al. 2005