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Cloud street to lee of Porto Santo (Madeira)

PostPosted: 2015 Oct 15, 21:41
by Eddy Graham
I hope you don't mind but I thought I would share the following two interesting images here:
1) A photograph I took of a cloud street to the lee of Porto Santo (Madeira) whilst on an airplane recently:
tn_Madeira-lee-street.png
tn_Madeira-lee-street.png (180.31 KiB) Viewed 1889 times

2) The same cloud street as seen by the MODIS Terra sensor (VIS & IR channels combined) that same afternoon:
20Jun2015_Porto-Santo_Maderia-MODIS_day171.jpg
20Jun2015_Porto-Santo_Maderia-MODIS_day171.jpg (26.54 KiB) Viewed 1889 times

Due to the shallow trade-wind inversion to the east of the Azores high, the steep volcanic islands of Madeira and the Canary Islands frequently obstruct the otherwise smooth flow of moist surface air from the north/north-west. This maritime layer is usually capped at low-levels (~1,000m) by a very strong quasi-permanent temperature and humidity inversion, caused by the descending arm of the Azores high / Hadley Cell - skies are usually clear above 1000m. The blocking of the shallow maritime layer of stratocumulus often yields beautiful and intricate patterns in the stratocumulus clouds downwind of the islands, such as Von Karman vortices, etc.. on this occasion we have a lovely bow-shape of cloud, with a single cloud street directly in lee of the island (presumably where pressure is lower and thus convergence is greater).
This is also one reason why the high volcanic peaks of the Canary islands are highly sought after as a destination for astronomical observation.
Eddie Graham, Stornoway