Learning from Extra Tropical Storm Case Studies

As mentioned, cold-core storms are generated when warm air masses collide with cold air masses and spin into a convective cell. The following video, produced from satellite imagery of extratropical system Yvette from May of 2014, shows how the storm formed over the Adriatic Sea east of Italy and moved eastward over the Balkan region where it led to heavy, intense rain and very strong winds that led to significant damage.

In the first part of the video, you will notice that a significant amount of water vapor enters the atmosphere and the clouds begin to form and rotate into a counter-clockwise spiral. As the storm forms and becomes more symmetrical, it moves over land, eventually weakens and falls apart as it dumps its precipitation. In the second half of the video produced from a different satellite tool for the same time period, warm colors represent warm air masses and white and greens represent relatively cooler air masses. In the video, a ridge (a northward projecting elbow) of warm air forms just off the coast of Spain and Portugal in the Atlantic. Immediately to the east, a trough (a southward projecting elbow) of cooler air descends into the Mediterranean Sea from France and Germany. This trough is followed to the east by another ridge in the area of the Adriatic Sea in the far eastern portion of the Mediterranean Basin. These ridges and troughs are formed as a result of movement of the jet stream in the upper-level of the atmosphere. Where these air masses intersect, they generate the counter-clockwise rotation of the extratropical storm system. The storm rotation intensified and became more organized as additional water vapor entered the atmosphere over the Adriatic. As a result, intensive winds were generated and significant rainfall produced widespread flooding in southeast Europe, especially in Serbia and Bosnia on May 14 and 15th of 2014. In fact, Yvette produced the worst flooding ever recorded in the region and contributed to numerous deaths. This video from YouTube and BBC TV shows some of the flooding to hit Serbia as a result.