A method and apparatus for simulating a windshear. A vortex is modelled in terms of a family of concentric streamlines and the position of an aircraft is defined with respect to the vortex as the aircraft traverses a reference plane. Four or more vortices are used to generate streamlines which match those encountered in an actual microburst. Each vortex placed above the simulated ground level is matched by a vortex of equal strength but opposite rotation placed below the simulated ground level at a distance equal but opposite to the height of the vortex above the ground. Strengths, distance from the vortex center, and height of the vortex may be programmed by the user. The high degree of flexibility permits accurate reproduction of the winds generated by actual microbursts for testing and developing microburst detection devices. The use of an algorithm which may be dynamically varied as a function of aircraft position obviates the need for simulating by discrete windshear magnitude as in conventional predetermined windshear tables and minimizes data storage requirements.