Recurving of Cyclones

One of the most important aspects of cyclone track forecasting is recurvature, A cyclone track is said to recurve when it changes its path from the predominant zonal flow (normally westwards) to predominant meridional flow (normally northwards) and often again back to zonal flow in the opposite direction (normally eastwards).

The recurvature is said to be abrupt if the meridional flow is short-lived and there is sudden change in the direction of more than 60°.

Tropical cyclones in both the Northern and Southern Hemispheres tend to move westward and drift slowly poleward and then eastward. Trade winds are responsible for the general westward motion of tropical cyclones (Environmental steering). 

Reasons for Recurving

• Coriolis force drifts the cyclones towards right in N.H (Ferrell’s law) and hence pole wards and then eastwards (Beta Drift). 
• Presence of subtropical highs, over oceans poleward of the trade winds. These regions of clockwise circulation in the Northern Hemisphere make the winds on the western edges of these large-scale circulations move toward the poles. 
• Interaction of tropical cyclones with mid latitude westerlies change the original westward path of tropical cyclones towards north and then eastwards.
• Upper air jet streams further push the cyclones towards right.
• Interaction among several cyclonic wind system, a new avg point of centre is made and cyclones changes its path (Fujiwara effect).