Whales Mouth

On Wednesday 7 July I knew that storms and showers could develop but I wasn't expecting too much. In the mid- to late morning hours storms developed southwest and west of Tirgu Mures. They already clustered a bit, and when the leading edge passed my location this phenomena appeared:



This cloud formation is called a whale's mouth. It marks the leading edge of cold air expanding from beneath a thunderstorm. With some imagination it looks like the inside part of whales' mouth.....




"A whale's mouth forms when a downdraft of cold air descends from a thunderstorm. Upon reaching the ground, the pool of cold air spreads out, much like a puddle of water expanding. At its leading edge, it forces the warm, moist air surrounding the thunderstorm to rise and cool. This cooling causes moisture in the warm air to condense, producing the whale's mouth cloud.
The boundary between the warm and cold air is very turbulent, which is what gives the cloud its gnarled appearance."









In the direction of the city of Tirgu Mures (that's looking SSW) I saw a rather conspicious lowering with several tuba-like clouds. However, rotation was not observed, so it wasn't a tornado......
















It became clear that the storms clustered together and a linear system was developing. This was confirmed by radar later:


Storms were moving from SW to NE while the line is oriented NNE-SSW, so storms are almost moving along the line.
This is quite common and often observed in squall lines. It is the repeatedly formation of new storms on the front of the line, what causes the W-E propagation of the whole system.


propagation = movement of the individual cells + development of new cells