Tropical storms

Tropical Storm

A rotating system of clouds and thunderstorms with wind speeds between 39-73 mph, forming over tropical or subtropical waters.

Storm surge

a rapid rise in sea level in which water is piled up against a coastline to a level far more than the normal conditions at high tide

Produced during the passage of a tropical storm when wind-driven waves pile up water against a coastline combined with the ocean heaving upwards as a result of much lower air pressure

characteristics of a tropical storm

200-700km in diameter

broad area of low pressure that encircles the globe either side of the equator

low pressure

once the system reaches maturity a central eye develops - an area of 10-15km in diameter in which there are calm conditions,clear skies,higher temperatures and descending air

conditions needed for the formation of tropical storms

Warm ocean water above 26.5°C, moist air, Coriolis effect, low wind shear.

outline the formation of tropical storms

• warm ocean (+26) causes warm moist air to rise this is convection

• the rising air cools and condenses forming clouds

• condensation releases latent heat that further warms the air and it rises, cools and condenses, and releases further latent heat - this forms continuous upward convection currents

• as the storm develops warm moist air is drawn into the low-pressure system over the warm ocean providing more fuel this is called convergence

• the rising air rotates due to the Coriolis force, forming convection currents into one tropical storm

distribution of tropical storms

found in linear pattern along the tropic of cancer and capricorn in bands 5-20 degrees north and south of the equator

storm moves away from the equator in a gentle curve due to the coriolis effect- because these are the only water that warm above 26 degrees which is required for sufficient convection to fuel storms

what is used to measure magnitude of tropical storms

saffir simpson scale :

a five point scale based on solely upon wind speed

problems with saffir simpson scale

it only predicts the damage from winds but in recent years nearly 90 % of tropical storm deathd in the usa were not a result of wind but water from storms surges,flooding and extreme rains

how has climate change impacted the magnitude,frequency and lifespan of tropical storms

studies have shown there was a great increase in the number of cyclones

this is due to the rise in ocean temperatures which leads to an increase in the air temperature above the warmer water resulting in enhanced uplift and local lowering of atmospheric pressure oceanic evaporation and a corresponding increase in atmospheric water vapor content

these two factors then result in parcels of very moist air rising which upon cooling with altitude releases huge amounts of latent heat in the form of condensation further enhancing uplift

slower-moving tropical storms are more common as polar areas get warmer there is increasingly less difference in atmospheric pressure between the poles and the tropics which reduces the speed of winds between the two areas which carries the tropical storms

slower moving storms produce more rainfall which is further enhanced by the greater amount of water carried by the storm due to higher ocean and air temperatures

physical and human factors affecting the vulnerability of a population to a tropical storm

• the intensity of the storm

• speed of movement ,the length of time over the area

• distance from the sea

• physical geography of the coastal area

• preparation made by community

• warnings and community response

major impacts that a tropical revolving storm can have on an area are

winds- can often exceed 150km/h which can cause structural damage to buildings roads and bridges,can bring down electricity transmission lines, and devastate agricultural areas

heavy rainfall - can bring about severe flooding,landslides and mudslides

Storm surges- can cause deaths and agricultural areas can take a long time to recover as soil is contaminated by seawater.

short term and long term responses for hurricanes

weather bureaux can access data from Weather satellites that give a real-time view of the location,track, size, and strength of the hurricane

they also investigate potential hurricanes and gather data with specially adapted aircraft and weather balloons

powerful supercomputers analyze the data from these sources and compare it to the historical data from previous storms- these can help to predict the strength of storms and people can be warned to evacuate

hurricane drills can be practiced

short term and long term responses to cycloens

as cyclones tend to follow an erratic path it is not always possible to give more than 12-18 hours of warnings this means insufficient time for proper evacuation

cyclone preparedness programs

mitigation

FEMA has a handbook with suf=ggestions on how to reduce damage to infrastructure for ecmaple making roads ,bridges etc as resilient as possible

for homeowners they have produced a factsheet with asvice on how people can protect their homes from flood and wind damage from waterproofing all external walls to fixing down roofs to the rest of the building and insurance

prevention

cannot be prevented but has been attmepted

seeding clouds with dry and sivler iodide so that storm losesmore water over the ocean ans therefore has less latent heat energy to be relased on lond

cooling the ocean with icebergs to reduce evaporation

adaptation

land use planning: limit certain types of development in such risky areas

building sea walls and barriers and putting houses on stilts is very expensive so unlikely to be kept on repeat

limiting expenditure on developments in high-risk areas directing the population away from them

retrofitting so that they are wind resistant and safer during an event in poorer areas the need for land usually outweighs the planning considerations to avoid high-risk areas so retrofitting is important

hurricane katrina hazard

wind speed: 280 kmph

saffier simpson: 5 (3 at landfall)

airpressure: 902mb

storm surge :10m

rainfall: 380mm/12hrs

characteristics of the place

environment

• low lying river delts

• protection-levees (they were not prepared for the levees to break)

economic (USA has $19t GDP but)

• one of the poorest cities in america

• low tax base led to low levels of maintenance of levees

• inadequate insurance provision

Socio-cultural factors

• distrust of government due to history of neglect /slavery led to poor response to evacuation order and relief effort

political factors

• response-state of emergency was not declared until 48 hours before event leaving insufficient time for evacuation

• emergency rescue and relief was delyaed due to lack of co-ordination

• FEMA did not act on models which predicted disaster

impact

• $ losses-200b

• death toll-1242

• homeless-1m

• displaced-1m

• properties destroyed-110000

Typhoon haiyan-hazard

• wind speed-250kmph

• saffier simpson-5

• air pressure-895mb

• storm surge-6m

• rainfall-300mm/12hrs

place

environment

• low lying archipelago (cities on coast)

• no extensive defences,especially from sea

Economic (USA has $300b GDP but trembled since 2005)

• rapidly industrialising and urbanising (1/3 live in property)

• speed of the development hinders land use planning

• low tax base limits invesment in emergency response

• rapid urbanisation concentrating people in vulnerable coastal areas

socio-culturcal factors

• many people lack education to understand how to protect themselves and respond

• rapidly growing population with on average 240 people per km2 and up to 2000 people per km2 in some areas

political factors

• inefficient hazard management e.g the typhoon shelters were too weak

• a state of emergency was declared but

• a widespread looting and violence took place

• local government virtually collapsed as many city officials were victims

impact

• $losses- 3b

• death toll-6200

• homeless-2m

• displaced-6m

• properties destroyed-all

Which was the worst disaster?

typhoon haiyan because death toll was 6200 ,2m homeless therefore had a higher impact whereas katrinas death toll was 1242 but katrina has the greatest economic cost

do the hazard characteristics best explain the difference

no becasue katrina has amore intense characterictics of hazard with a windspeed of 280km/h and 10 m storm surge but had a lower impact than haiyan which has a 6m storm surge and widspee dof 250km/h .Katrina has the worst hazard which partly explain the costs arising from storm

do the characteristics of the people/place best explain the difference?

Typhoon Haiyan had no extensive defenses from the sea, densely populated, inefficient hazard management which the city was not prepared, informal housing

FEMA failed to strengthen the levees in New Orleans and the evacuation and emergency services was flawed but this still saved lives

human responses

hurricance katrina

positive actions

• media backlash led to extensive rehabilitation nad reconstruction ($15b for H.Sandy) e.g the great wall of louisiana,18 mile long concrete wall

poor resonses

• president was not prepared

• delayed response-looting and homelessness

• relief was poor and few deaths

• depopulation

• disadvantaged african americans

overall

short term repsonses were inadequate but long term was slow but effective and large scale

typhoon haiyan

positive actions

• 90% recovered

• families ordered to relocate to relocation sites

• us and uk navy supported un and aid agencies which was active in 24 hours

poor response

• new houses have issues like electricity and water supply

• people still live in danger zones

• no available work

• 30% complete by 2018

• poor sanitation

overall

limited but good intention but ineffective

What characteristics would a good risk management have

• saves most lives

• mitigates as much damage as possible

• affordable/appropriate to the place

evaluate risk management strategies designed to reduce impacts of tropical storms

1. Land use planning-reduces social and economic losses and its cheaper

2. hurricane forcast and warning systems-information can be shared and gives time for evacuation

3. hurricane resistant building design-will reduce impact on infrastructure which may also reduce deaths due to buildings etc but it is expensive

4. hurricane modelling-enables long term preperation but requires practical action

5. emergency service training-many LEDCs do not have extensive emergency services or the finance to stock pile resources

6. education-limited in LEDc due to lack of education system

7. emergency action

8. insurance-only prevents personel economic losses and doesnt stop deaths but good at recovering

9. could seeding-has been unsuccesful and could make storm even worse