Gorgeous Kelvin-Helmholtz Waves over the English Channel! (credit: Samphire Hoe via Meteo Europe)

DISCUSSION: During the late afternoon hours on Thursday across coastal sections of western Europe and specifically towards the British Isles, there was a particularly interesting weather pattern in place.  This weather pattern was characterized by a substantial amount of vertical wind shear in place between the surface and much higher up in the atmosphere.  Although wind shear is most often associated with being a factor and catalyst of severe thunderstorms developing rotation and sometimes helping such storms to generate a tornado, wind shear in this part of the world often has other consequences.  

In addition to winds sometimes being found to change direction with height, there are also situations in which winds will not change direction with increasing height.  In these alternative scenarios, the winds will instead be found have different speeds at different levels of the atmosphere (while still maintaining the same direction of flow).  It is in these situations that we most often find visual manifestations of this change in wind speed with increasing height within or near a given cloud deck.  This is a direct consequence of this unidirectional flow at different or even slightly different heights causing clouds to "spiral" around themselves and be observed as "Kelvin-Helmholtz" waves.  To provide some background on the history behind Kelvin-Helmholtz waves, it is important acknowledge that this atmospheric cloud phenomena was named in honor of Lord William Thompson Kelvin and Hermann von Helmholtz who collectively studied the atmospheric dynamics behind this picturesque atmospheric phenomena.

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©2017 Meteorologist Jordan Rabinowitz