Mesocyclone

 
Pure Rotation
 
 
Cyclonic Rotation
 
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Mesocyclone Algorithm
 
    Algorithm triggers with shear perpendicular to the radar beam exceeding 5 m/s/km, with the typical mesocyclone being 3 to 8 km in diameter.  
 
 
 Exeter radar May 23, 2000. A example of a low-topped supercell that spawned an F2 tornado.
 
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Plotting of mesocyclones
 
    Coloured circles are used, though the implications on single radar products are different than those on composite products.
  • Single radar products: colour and the size of the meso are used to plot the circle. The circle is 4 times the diameter of the meso. Given the typical radius of the mesocyclones, the circles should be 15-35 km wide. Large circles may be indicative of the algorithm triggering on shears that are not mesocyclones. 
      The colour scheme used can be interpreted as follows:
  • Green circle (codes 1-2)
    • thin ... shear threshold exceeded at 1 elevation angle
    • thick ... shear threshold exceeded at 2 angles
  • Yellow circle (code 3)
    • meso at all three angles. For most of the radar's range, except the closest, yellow implies shear with significant depth.
    • not common
  • Orange circle (code 4)
    • meso plus angular velocity v2/r of mesocyclone exceeds 150
  • Red Circle
    • code 4 plus shear confirmed across multiple azimuths
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