spinDegreesPerSecond

Rotation speed in degrees/second when spin is true. Positive spins counter-clockwise on screen, which is the cyclonic direction in the northern hemisphere; factor flips it per feature for southern-hemisphere storms.

The default is +180 even though the equivalent JS tropical shader hook reads symbolAngle += (time * -PI * 2.0) * 0.5 * factor — i.e. -180 deg/s. The magnitude matches; the sign does not, because the two renderers apply the rotation on opposite sides of the matrix. JS does pointPosition.xy *= rotationMatrix (vector-times-matrix, so the transpose) while SYMBOL_VERT does rot * corner. Copying the JS number verbatim therefore spun the icons backwards, which is what this default used to do.