Detecting tropical cyclone genesis from remotely sensed infrared image data

An objective technique to discriminate developing from nondeveloping cloud clusters during tropical cyclogenesis is described. Since vortices are characterized by high levels of organization or axisymmetry, their detection at early stages of the lifecycle of tropical cyclones makes it possible to determine when they form. To quantify the axisymmetry of a cloud cluster around a predefined radius, a statistical analysis of the orientation of the brightness-temperature gradient is performed. Results show that early detections of axisymmetric structures reliably indicate the cyclone genesis on an average of 0.6 h before an atmospheric disturbance becomes a tropical depression. In addition, the technique shows potential to discriminate nondeveloping from developing cloud clusters. A statistical analysis shows that a true-positive rate of detection of approximately 93% could be achieved with a false-alarm rate of 22%.