Tornado Observations

• When there is a good chance of tornadic formation within the next few hours, a tornado watch is issued by the Storm Prediction Center in Norman, Oklahoma (http://www.spc.noaa.gov/)
• When a tornado has been spotted by:
  • trained spotter
  • on radar

  then a tornado warning is issued

Observation with a radar:

• We now have a national network of radars called the Weather Surveillance Radar (WSR-88D) that can observe tornadic storms
• recall that the tornado forms from the mesocyclone at low levels.
• the mesocyclone can be observed with a radar and is called a "hook echo"
• Here is another example of a hook echo
• Important!!!: the radar can not see the tornado itself since the scale of the tornadic circulation is very small (on average 100 m wide).
• The radar can see the mesocyclone which is 2-4 km wide.