by Philip Lutzak  


All storm images on this page courtesy Jean-Pierre Scherrer.



  The incredible photo above was taken at Versoix am Genfersee, at the southern end of Lake Geneva, Switzerland, after an intense storm on January 26, 2005. Winds gusted to 31 meters/sec (70mph) as temperatures dropped to -12 to -7 Celsius (10 to 19F), causing massive waves and sea spray to encase everything near the shore in sheets of ice. Please scroll down for a little background, some weather analysis and more pictures of this event.




Figure 1. Map of Switzerland and surrounding countries. Versoix is at the lower left. Courtesy Perry Castaneda Library.

 Versoix am Genfersee is a small village on the southwestern shore of Lake Geneva, Switzerland at latitude 46 degrees North. It has a temperate climate, with an average annual temperature of 10C or 50F. It sits at an elevation of 415 meters or 1364 feet.


Figure 1a. Close-up of Lake Geneva. Courtesy Perry Castaneda Library.

  Because of its location in the westerly flow of weather systems in the temperate zone (the mid latitudes between 30 and 60 degrees North), low pressure areas occasionally cross over Versoix during the cold season, producing wind with rain or snow. The following is a short explanation of why this particular system was so powerful.



   The atmosphere is always trying to stabilize itself by moving the air from high to lower pressure, and the pressure gradient, or difference in pressure, between the highs and lows determines how strong the winds will be. On this occasion, a particularly strong area of low pressure developed over the Mediterranean Sea and was then cut off between 2 areas of very strong high pressure to its east and west. Since air blows clockwise around high pressure and counterclockwise around lows, the air over northern Europe was forced rapidly southward towards the center of the low over Italy (2005-01-26 surface pressure chart). Because of the especially steep pressure gradient between the huge Atlantic high and strong Mediterranean low, northeast winds of considerable speeds developed and raced through the northern Alps of Switzerland and northern Italy. As the winds came across Lake Geneva and blew towards the southwest end of the lake, they brought in much colder air form the north, dropping temperatures precipitously, while at the same time driving the water level way above normal. This set the stage for a huge ice storm as large waves overcame the seawall, coating everything with sheet after sheet of ice as temperatures fell well below 0 degrees C. For the meteorological record from the period, here's the weather charts from 2005-01-26 and 01-27, courtesy The Weather Underground.

  For something technically deeper, here are the 2005-01-26 300mb chart, showing the jet stream level pressures and flow (9,000 meters or 30,000 feet), and the 2005-01-26 500mb chart, showing the flow and pressure at mid level (5,500 meters or 18,000 feet). 


  Following are more incredible photos taken after the ice storm. All photos are courtesy Jean-Pierre Scherrer.













For more photos, please see Jean-Pierre's website: