This is a good example of Von Kármán vortices that developed to the lee of the island of Madeira.
27 May 2022
06 March 2008
By Andreas Wirth and Jarno Schipper (ZAMG)
The pattern often forms on the lee side of mountainous islands during a situation with stratiform clouds (e.g stratocumulus sheets) moving around on the east side of a sub-tropical high pressure system.
The circumstances in which these vortices' are formed are characterised by a layered buildup of the troposphere. In the layer from the surface up to 850hPa there is usually less wind than in the 'free atmosphere'. Because there is almost no mixing between the two layers an inversion can persist for some time. Such inversions often occur in the vicinity of high pressure systems.
The island causing the vortices has to be high enough to penetrate the inversion. In addition, there need to be wind speeds of five to 15m/s in the lowest layer. With wind speeds less than this threshold the vortices can not develop. Higher wind speeds do not guarantee that the vortices are maintained.
Once the vortices have formed they follow the guiding airflow and dissolve when they reach an area where the temperature buildup of the troposphere is different. This pattern was first discovered in the atmosphere in 1962 with the help of the American weather satellite TIROS V, until then this feature had not been detectable in the atmosphere.
Similar Von Kármán vortex cases
Von Kármán vortex street near Madeira
Downstream to the west of the isle of Madeira, a von Kármán vortex street can be seen.
Von Kármán vortex streets to the lee of the Canaries
Von Kármán vortex streets to the lee of the Canary Islands in June 2005.
Low cloud vortices off coast of Morocco
On 10 July a low cloud vortex was spotted off the northwest coast of Morocco.