Step 7. Construction of the Left and Right Radial Lines.
a. Measure the angle formed by the radial lines drawn from ground zero
to the cloud-top height and two-thirds stem height points on the
fallout vector plot (or the radial lines which have been expanded to
include vectors between the two-thirds stem height and the cloud-top
height). If the angle formed is 40 degrees or greater, proceed as
outlined in Step 8.b. If the angle formed is less than 40 degrees,
bisect the angle and expand the angle formed by the two radial lines
to 40 degrees, 20 degrees on each side of the bisector, (Figure
b. Measure the azimuths, in mils or degrees from grid north, of the
final left and right radial lines and record on lines p and q of the
worksheet (use four digits).