Tropical storms: formation and hazard management
Geography · GCSE · The School
The conditions a tropical storm needs
Ocean temperature above roughly 27°C, to a depth of at least 50 metres, provides the energy. Warm, moist air rising creates low pressure that draws in more air. The Earth's rotation makes the rising air spin (the Coriolis effect), which is why tropical storms never form exactly on the equator, where that spin is zero.
Structure: the eye and the eyewall
The EYE at the centre is calm, with light winds and clear skies, as air sinks there. Surrounding it, the EYEWALL has the storm's most violent winds and heaviest rain, as warm moist air spirals rapidly upward. Spiralling RAIN BANDS extend outward from the eyewall, bringing heavy rain and gusty wind well beyond the storm's calm centre.
The hazards a tropical storm brings
High winds can exceed 150 mph in the strongest storms, damaging buildings and infrastructure directly. Storm surge — seawater pushed ashore by the storm — causes most tropical storm deaths, often more than the wind itself. Heavy rainfall causes flooding and landslides, sometimes long after the storm has otherwise passed through.
A worked example: naming the hazard, not just the storm
A coastal town is hit by a tropical storm. Reporting only "the storm hit the town" earns little. A full answer names which specific hazard caused which specific damage: the storm surge flooded the ground floor of coastal buildings, the high winds tore roofs from inland housing, and the heavy rain triggered a landslide on a nearby slope two days later.
Prediction: buying time before landfall
Satellites track a tropical storm's position, size and strength continuously as it develops. Computer models forecast its likely path, though the further ahead the forecast, the less certain the exact landfall point becomes. Warnings issued days ahead give time to evacuate — the single most effective way to reduce deaths, even though property damage cannot be prevented this way.
Management: reducing the impact where it lands
Building codes requiring storm-resistant construction reduce wind damage. Coastal defences and evacuation routes reduce deaths from storm surge and flooding. Aid and emergency response speed recovery after the event. Poorer countries, with less money for building codes, defences and organised evacuation, generally suffer more deaths from a similarly strong storm than richer ones.