Smoke tests at full scale

This amazing photo was shot by Daniel Forster from a helicopter at the start of the Volvo Ocean Race in Cape town.

The phenomena came about as there was an inversion (layers of different temperature air on top of each other) and the cold seawater (16 deg Celsius) causes a sea smoke in the warm, moist air (27 deg Celsius). The inversion builds a roof at the level of the top of the mast of the boats. The airflow between the sea surface and the inversion layer is laminar and does not mix with the upper flow, hence the wind does not blow away the wakes behind the sails as it normally would.