A mathematical model for forecasting tropical cyclone tracks

The kinematics and dynamics of tropical cyclone (TC) tracks are studied by using a mathematical model of track curvature. The results indicate that the curvature of storm track is determined by a set of ‘controlling parameters’ related to the storm characteristics and the ambient atmospheric circulation. These controlling parameters include the speed of storm motion, storm intensity and size, the Coriolis parameter, ambient atmospheric pressure field, and surface friction. In northern hemisphere, a northward moving TC tends to gain anti-cyclonic curvature and deflect to the right. A westward or northwestward moving TC will also deflect to the right when it slows down. A westward-moving TC along the southern edge of the sub-tropical high tends to deflect to the right as it moves toward the “turning point” of the large scale flow field (i.e. the southwest corner of the subtropical high). An eastward-moving TC along the northern edge of the sub-tropical high tends to deflect leftward toward the low-pressure side of the steering flow. A TC located in front of a westerly trough will gain cyclonic curvature. Thus, a re-curving TC after passing its western most location will tend to deflect to the low-pressure side. Finally, TC intensity and size change can also affect the TC movement. For example, a westward moving, deepening or enlarging TC tends to move anti-cyclonically.