Track Forecast Cone - Basics

Basics

The large scale synoptic scale flow determines 70 to 90 percent of a tropical cyclone's motion. The deep-layered mean flow through the troposphere is considered to be the best tool in determining track direction and speed. If storms experience significant vertical wind shear, use of a lower level wind such as the 700 hPa pressure level (at a height of 3,000 metres (9,800 ft) above sea level) will work out as a better predictor. Knowledge of the beta effect can be used to steer a tropical cyclone, since it leads to a more northwest heading for tropical cyclones in the Northern Hemisphere due to differences in the coriolis force around the cyclone. For example, the beta effect will allow a tropical cyclone to track poleward and slightly to the right of the deep layer steering flow while the system lies the south of the subtropical ridge. Northwest moving storms move quicker and left, while northeast moving storms move slower and left. The larger the cyclone, the larger the impact of the beta effect is likely to be.