White squall

A white squall is a sudden, violent windstorm at sea that strikes without the dark clouds that normally mark an ordinary squall, appearing instead as an abrupt surge in wind over tropical or subtropical waters and sometimes taking the form of a microburst. It takes its name from the white-capped, broken water it whips up, which is often the only warning a sailor gets; the phenomenon is rare on the open sea but occurs fairly often on North America's Great Lakes.