EARTHSC 2GG3 Lecture 11: Lecture 11 - Tropical Cyclones.docx
1 Apr 2013
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Document Summary
The main development regions are between 5deg and 27deg north and south of the equator. Low pressure warm air from ocean can rise and with it moisture is taken up. Convergence low p system; then diverge. Heat released as water condenses and then rises again. Warm ocean water (>26. 5c) to a depth of 20 m. Convergence of air masses to form areas of low pressure. Growth of a tropical cyclone: tropical disturbance. Thunderstorms developed in a zone of convergence can cluster. Condensation and release of latent heat continues to warm air: tropical depression. Minimum wind speed of 40km/h ; low p system. Convection spiral and rotation develops as warm air spirals upward. Decreasing pressure at the surface increases wind speed and subsequent evaporation: tropical storm. Eye forms as warm air from the high-pressure aloft is sucked down into the centre: tropical cyclone. Officially becomes a tropical cyclone when sustained wind speeds exceed 119km/h. Eye wall most precipitation, highest wind speeds.
