1b.1 DM - Causes of tropical storms Flashcards
Why do some hurricanes increase/decrease in intensity?
They pass over warmer/cooler areas of water
Why do some tropical storms create more flooding?
They create a larger storm surge
The intensity of the storm means air pressure is lower, and the surge of sea level (local-scale rise) is greater
How warm does water have to be to create tropical storms?
27oc
What do tropical storms need to grow / develop?
Water
Warm water
Near the equator but not on so the coriolis force starts them spinning
Where do tropical storms form?
5-10o N/S of the Equator
The earth’s spin causes them to spin (Coriolis force)
When do tropical storms form in the Northern Hemisphere?
July to September
Where does the energy for a tropical storm come from
Latent heat - from the condensation of the rapidly rising evaporated water from the ocean
What causes the tropical storms to move towards land
Strong trade winds
When are tropical storm seasons in different parts of the world?
Atlantic - Hurricanes - July to Sept
Indian Ocean - Typhoons - July to October
Southern Indian Ocean - Cyclones - January to April
How are tropical storms measured?
Wind speed - on the Saffir Simpson Scale
1-5 (5 is worst)
What happens at tropical storm source areas?
Warm oceanic water (27oc) either side of the Equator begins to evaporate at the surface
Air rises through convection, heavy with water vapour.
Leaves low pressure area at the surface of the water, which sucks in more air from the surroundings.
What is a tropical storm ‘eye’?
Air that sinks within the eye wall results in high pressure at the centre of the cyclone
It’s calm, with cloudless skies
Strongest winds surround it
Where do tropical storms go?
Trade winds blow the storm west over the ocean – the tracks
Over land, no moisture / energy coming in = storm dies out
Where does energy for tropical storms come from?
Condensation: releases latent heat energy to power the TS
As air rises it also rotates, creating a vortex around an eye wall (stronger winds around eye)
When the rising air reaches the top of the cyclone, the air flows away from the centre, (layer of cirrus clouds continues to spin)
Why are tropical storms so ‘stormy?
Air flowing away cools and sinks back to the ocean where the warm ocean water heats the air again, causing it to rise and continuing the cycle.
Cyclical convection of warm, moist air results in bands of thunderstorm clouds on either side of the eyewall.
