Hereâs why I chose the NASM certification! Did you need any sort of background related to the field going into the program? Nope, you just need to make sure that you have a current CPR and AED certification before you take the exam. How long does your certification last before you have to renew it?
Tornado Warning. This is issued when a tornado is indicated by the WSR-88D radar or sighted by spotters; therefore, people in the affected area should seek safe shelter immediately. They can be issued without a Tornado Watch being already in effect. They are usually issued for a duration of around 30 minutes.
Some tornadoes strike rapidly, without time for a tornado warning, and sometimes without a thunderstorm in the vicinity. 1  When you are watching for rapidly emerging tornadoes, it is important to know that you cannot depend on seeing a funnel: clouds or rain may block your view. The following weather signs may mean that a tornado is approaching: 1  A dark or green-colored sky. 2  A large, dark, low-lying cloud. 3  Large hail. 4  A loud roar that sounds like a freight train.