Dynamical causes of Echo Training in The Southern Swiss Alps

Austin Wardall

ERAU

Maggia Valley Flash Floods

• Major Hazard

• Related to Echo Training– Convective cells repeatedly triggering at

the same location and following the same storm track

Procedure

• Modeled four major echo training events using the WRF-EMS mesoscale atmospheric research and forecasting model

• Investigated the four simulations for similar precipitation patterns to those observed by Swiss operational radar data

• Proceeded with a graphical study of dynamical conditions supporting orographic convective triggering upwind from the Maggia River

Pre

cipi

tatio

n E

vent

s

(Panziera et al., 2014)

Topographic Map of Northern Italy and Switzerland

Modeled Precipitation Events

17-18 Aug. 2006 5-7 Sept. 2008

“Good” Simulations

Modeled Precipitation Events

5-6 June 2009 25-26 Sept. 2012

“Bad” Simulations

Dynamical Findings

Lee Troughing and Cyclogenesis

950mb relative vorticity and streamlines with 1km reflectivity

17 Aug. 2006 1900Z 5 Sept. 2008 1700Z

“Good” Simulations

Lee Troughing and Cyclogenesis

950mb relative vorticity and streamlines with 1km reflectivity

6 June 2009 0100Z 26 Sept. 2012 1800Z

“Bad” Simulations

MSLP

17 Aug 2006 1900Z 7 Sept. 2008 0200Z

“Good” Simulations

MSLP

6 June 2009 1900Z 26 Sept. 2012 2100Z

“Bad” Simulations

Low-level Moist Jet

950mb dewpoint and streamlines with 1km reflectivity

17 Aug. 2006 2200Z 7 Sept. 2008 0500Z

“Good” Simulations

Low-level Moist Jet

950mb dewpoint and streamlines with 1km reflectivity

6 June 2009 0800Z 26 Sept. 2012 1800Z

“Bad” Simulations

Conclusions

• The model more accurately simulates the location of convection when it captures lee troughing to the north of the Appennine Range

• The lee troughing to the north of the Appennines may contribute to the formation of an easterly barrier jet along the southern slopes of the Alps

• The convergence of this barrier jet with moist southerly low-level flow from the Mediterranean over the southeast-facing Alpine slopes seems to be the main trigger leading to flooding in the Maggia Valley

Citations

Panziera, L., C. N. James, and U. Germann. "Mesoscale organization and structure of orographic precipitation producing flash floods in the Lago Maggiore region." Quarterly Journal of the Royal Meteorological Society (2014).

Acknowledgements

• Dr. Curtis James, ERAU

• Luca Panziera, University of Trento

• Dr. Gary Yale, ERAU Space Grant