Key terms Flashcards
tropical disturbances
is defined as an area or organised thunderstorm activity 100 - 300 miles in diameter which maintain its identity for 24 hours of more. Forms when sea is 26.5C or above
tropical cyclones
a rotating storm system characterized by a low pressure centre, a closed low level atmospheric circulation, strong winds, and a fast spiral arrangement of thunderstorms that produce heavy rain
Hurricanes, typhoons, cyclones
Hurricane = atlantic ocean + north eastern pacific
typhoons = north western pacific ocean
cyclones = south pacific + indian
coriolis force
apparent force, due to the spinning of the Earth, which deflects movement of particles and wind
how do tropical storms form?
- need a lot of heat to form, usually why they lie over the equator, at least 26degreesC
- sun is close to the equator, providing energy to heat the ocean
- warm ocean heats the air above it causing it to rise rapidly
- water evaporates quickly from the warm surface water, so rising air contains great amount of water vapour
- rising air starts to spin, clockwise in the northern hemisphere
- the centre is calm
- as air rises, it cools, condenses and forms cumulonimbus clouds
- rapidly rising air creates an area of intense low pressure
- low pressure sucks in air causing very strong winds.
- once overland it fades
tropical storms as hazards
bring heavy rainfall, strong winds, mudslides
form between 5 and 30 degree latitude
move westwards due to easterly winds
IT IS HARD TO PREDICT THE PATH OF A TROPICAL STORM therefore difficult to manage
mature tropical storms
pressure may fall as low as 880millibars
this and strong contrast for outer part of tropical storm –> very strong winds OVER 118KM/h
Conditions needed for a tropical storm
sea temp must be over 27dC at a depth of 60m
low pressure area has to be far away enough from the equator so that Coriolis force creates sufficient rotation of the air mass
tropical storm definition
low pressure system up to 600km in diameter with wind speeds up to 300km/h, typically 160km/h. Bringing up to 30-5-cm of rainfall
Saffir simpson scale
measures the scale of tropical storm strength and impacts
Some saffir simpson categories
category 1: winds 119-53km/h, storm surge 1.2-.5 above normal
3: 119-209 with storm surges generally 2.7 to 3.6 above normal
5: winds 249km/h, storm surge greater than 5.5m
Tracking tropical storms
satelite images
aircraft that fly into the eye and record information
weather stations at ground level
radars that monitor areas of intense rainfall
Preparing for tropical storms
— risk assesment
— land use control
- – reducing vulnerability of structures
- new buildings wind + water resistant
- protective river embankments
- improved vegetation cover
Why is managing tropical storms difficult?
unpredicatbility of the storm path
people living in coastal areas increased risk
tornadoes
a mobile, destructive vortex of violently rotating winds having the appearance of a funnel-shaped cloud and advancing beneath a large storm system.
