Shear Line Algorithm

The Shear Line (SLINE) algorithm uses the uniform wind assumption.

1. The radial, azimuthal, or combined shear are computed using the SHEAR algorithm.

   The previous VVP wind is used to remove the apparent azimuth shear caused by the mean wind.

   The shears are computed using polar data and the output is then X-Y data to a selectable grid spacing.

2. The shear magnitude is thresholded with regard to strength and area within a specified area.

   Shear regions less than the threshold or smaller than the area limit are not considered.

3. The shear magnitude values of 2 elevations are ANDed.

   This step is optional if a second elevation is specified.

4. A curve is fitted to the shear field to detect a linear region.

   Points that fall outside the curve are eliminated, and the curve is refit.

   Only one shear line can be considered in a product.

5. The speed of motion normal to the gust front is obtained by comparing the data from the current shear line location with the data from the previous location.

6. The VVP wind is computed in both areas defined by the shear line using the uniform wind assumption.

7. The computed motion is projected to determine if and when the shear line will cross each protected area.

8. The results are output.