A cyclone warning is preceded by a distinct wailing siren called the Standard Emergency Warning Signal (SEWS). When you hear this sound, you should pay immediate attention to radio, television, or a mobile alert for an official emergency announcement and follow the instructions. The cyclone itself will make a loud, roaring noise like a jet engine, but the SEWS is the official warning siren sound. What it is: The Standard Emergency Warning Signal (SEWS) is a wailing siren used for major emergenci