Storm Hazards

Question 1

What are tropical revolving storms

Answer 1

Tropical revolving storms are systems of intense low pressure (up to about 600-700km across) formed over tropical seas.

Question 2

What are tropical storms like/ describe their behaviour

Answer 2

They move erratically until they reach land, where their energy is rapidly dissipated. At their centre is an area of subsiding air with calm conditions, clear skies and higher temperatures, known as the eye.

In all cases they only become a tropical revolving storm when the wind speeds exceed 120km/h. Such storms are predictable in their spatial distribution.

Question 3

What’s the eye of a tropical storm like

Answer 3

At the centre is an area of subsiding air with calm conditions, clear skies and higher temperatures, known as the eye.

Question 4

Tell me about the predictability of tropical storms

Answer 4

They are predictable in their spatial distribution. Hurricanes in the Caribbean are also predictable in their timing and frequency- usually towards the end of summer and into autumn. They are concentrated in the tropics, specifically between 5 and 20 degrees north and south of the equator.

Question 5

Once a tropical storm is generated, where do they move

Answer 5

Once generated they tend to move westwards initially, before then switching to a more northeastwards direction as they move further away from the equator.

Question 6

Tell me about the initial formation of tropical storms

Answer 6

Tropical revolving storms begin with an area of low pressure in the tropics into which warm air is drawn in a spiralling manner. Small scale disturbances enlarge into tropical storms with rotating wind systems, which grow into a much more intense and rapidly rotating system.

Question 7

What are the factors that largely determine this initial formation and subsequent transition of a tropical storm

Answer 7

There must be an oceanic location where sea temperatures are over 27 degrees c,

The location must be at least 5 degrees north or south of the equator so that the effect of the Coriolanus force (CF) can bring about the maximum rotation of air

Rapidly rising moist air (from the warm sea) cools and condenses, releasing latent heat energy, which then fuels the storm. Such storms fade and die over land as the energy source is removed.

Low level convergence of air occurs in the lower part of the system, but this is then matched by intense upper atmosphere divergence of air, together creating an up draught of air.

Question 8

Define Coriolis force (CF)

Answer 8

The effect of the earths rotation on air flow. In the northern hemisphere, the CF causes a deflection in the movement of air to the right, whereas as in the Southern Hemisphere to the left.

Question 9

List the hazards associated with tropical storms

Answer 9

High winds

Heavy rainfall

Storm surges

Question 10

Tell me about high winds as a hazard associated with tropical storms

Answer 10

High winds exceeding 150km/h, which cause structural damage and collapse of buildings, damage to bridges and road infrastructure, and loss of agricultural land.

Question 11

Tell me about heavy rainfall as a hazard associated with tropical storms

Answer 11

Heavy rainfall, often over 100mm a day, which causes river flooding and sometimes landslides, particularly in areas of high relief.

Question 12

Tell me about storm surges as a hazard associated with tropical storms

Answer 12

Storm surges result from the piling up of the water by wind driven waves and the ocean rising up under reduced atmospheric pressure - such coastal flooding can extend inland if the area near the coast is flat and unprotected.

Question 13

How is the magnitude of tropical storms measured

Answer 13

Measured on the Saffir-Simpson hurricane wind scale, which consists of 5 levels of central pressure, wind speed, storm surge and damage potential.

Question 14

Tell me about the Saffir-Simpson wind scale

Answer 14

1 = 120-153 km/h 
5 = 250+ km/h wind speeds 

1= no real damage to building structures, some damage to trees and vegetation, some risk to coastal flooding, storm surge 1.2-1.5m above normal water levels

5= complete roof failure on many dwellings and industrial buildings, major flood damage, massive evacuation of residential areas may be required. Storm surge 5.5+m above normal water levels

Question 15

What 3 categories do the management and responses to tropical storms fall into

Answer 15

Prediction, prevention, protection

Question 16

Tell me the management and responses to tropical storms about prediction

Answer 16

Predicting storms origins and tracks - a form of preparedness. This depends on the quality of monitoring and warning systems. It is essential that warnings are as accurate as possible. Forecasting the precise power and track of a tropical storm remains problematic. The USA maintains round the clock surveillance of hurricanes using weather aircraft in order to increase its preparedness.

Question 17

Tell me about using prevention for the management and responses to tropical storms

Answer 17

Ongoing research into how tropical storms can be tamed through mitigation. Much of this effort is directed at ways of reducing the storms energy while it is still over the ocean. One attempt has been to ‘seed’ the storm using silver iodide outside the eye wall clouds. The idea is to produce rainfall, so releasing latent heat that would otherwise sustain high wind speeds.

Better computer forecasting models. New technologies allow forecasters to break storms into a grid, and to use sophisticated methods to predict changes in wind speed, humidity, temperature an cloud cover. The national oceanic and atmospheric administration (NOAA) in the USA has a high resolution model to enable greater forecasting accuracy.

Schoolchildren in Florida practice hurricane drills, similar to those in earthquake-prone areas, as part of an awareness programme called project safe side.

Question 18

Tell me about protection for the management and responses to a tropical storm

Answer 18

Land use planning so that areas at highest risk have limited development, and therefore less potential economic damage.

Strengthening of buildings to withstand storms and floods, or erecting houses/ building on stilts

Construction of seawalls, breakwaters and flood barriers

Adequate insurance before the disaster, and aid during and after the event, which contributes towards modifying any loss.

Question 19

What may the impact of tropical storms depend on

Answer 19

A range of political and economic factors. Areas with lower levels of economic development suffer from a lack of insurance, poor land use planning, inadequate warning systems and defences, and poor infrastructure and emergency services. This usually results in a higher death toll. Even within a wealthy country such as the USA, hurricane Katrina exposed the problems of a largely uninsured and relatively poor population who struggled to cope during, and especially after, the event.