1. A method for detecting hazardous relatively small scale weather disturbances in an area of surveillance, comprising the steps of: radiating at least one Doppler radar beam toward a region of scatterers and scanning said beam in azimuth; receiving echo signals in at least first and second vertically overlapping beams from said scatterers in said first and second beams from a sequence of range bins, wherein the effective differential two way beam gain of said first and second beams is of a first polarity at all angles below a predetermined null level and of a second polarity at all angles above said null level, wherein said null level corresponds to the elevation angle at which the effective two way gain of said first beam equals that of said second beam, and wherein said first and second polarities may be mathematically operated upon selectively to provide first and second parameters equivalent to said first and second polarities; determining the respective Doppler velocity spectra from said first and second beams from said sequence of range bins; generating a composite Doppler spectrum which is a mathematical function of the Doppler spectra of said first and second beams, said composite spectrum defining the Doppler velocity domains wherein the two Doppler spectra differ in said first and second polarity senses; determining two velocity bounds in the region of said composite Doppler spectrum wherein said composite spectrum is of said first polarity; generating signals identifying the first of said two velocity bounds as a measure of wind speed at said null level; generating signals identifying the second of said two velocity bounds as a measure of wind speed at a level between the height of the null level and the surface of the earth, said wind speed being defined as the radial component of the near surface wind speed; measuring the near surface wind speeds in said sequence of range bins; selectively determining the range derivative of the near surface wind speeds, the tangential derivative of the near surface wind speeds, the difference between the first and second velocity bounds, the difference between the mean reflectivities in said first and second beams, and generating output signals corresponding thereto; and providing at least one indication of said output signals to thereby provide an indication of a weather disturbance in said area of surveillance, particularly the shear of the near surface winds including horizontal, vertical and tangential shear and the boundaries at which said shears exceed preset thresholds.