Squall

A sudden, substantial increase in wind speed that lasts longer than a brief gust.

A squall can accompany a shower, thunderstorm, cold front or line of convective cloud, but it is not defined by the presence of dark cloud or by one particular type of front. Wind direction may shift and heavy rain, hail, lightning or sharply reduced visibility may occur.

Its rapid onset can create high sail and rig loads and a sudden change in sea state. Forecasts, radar where available, cloud development and changes in temperature or wind should be monitored, and sail and deck arrangements should be adjusted before the squall arrives where possible.