hurricanes and tornadoes

rhian

hurricane def

• tropical cyclone (typhoon)

• rapidly rotating storm system

• thick clouds spiral around clear eye

• high pressure centre (950mb)

• strong winds (>32m/s)

• 500km diameter

hurricane structure

• most intense activity in eye wall

• conditions in the eye are calm

• centrifugal forces and pressure gradients cause spinning

• warm core causes high pressure and sinking air, stopping clouds from forming

conditions for hurricane formation

Atlantic hurricane season- 1st June- 30th Nov

• warm ocean surface temperatures (>26.5)

• water with a depth of 50m

• require convection and a strong Coriolis effect

• hurricanes form at 5-20 degrees N or S

• small amounts of wink shear

saffir simpson scale

• 1-5

hurricane dissipation

• tropical cyclones can last 7-20 days

• storms hits land or reaches cold waters

• supply of latent heat is cut off

• high wind shear

• weakens and dissipates over a few days

hurricane hazards

• strong winds- 120-250km/h

• heavy rain- 250mm/day

• storm surges

• secondary events- floods, landslides, tornadoes

hurricane katrina facts

• hit louisiana 29th august 2005

• category 3, 193km/h (119mph)

• most expensive hurricane ($108 billion)

• 1800 fatalities

• 7.5m storm surge

• weakened to a tropical storm following day

mitigation: evacuation

• mandatory- New Orleans

• 10-30,000 in New Orleans Superdome (sustained damage)

• Many stayed (poor, elderly, limited transport)

Mitigation: Flood protection systems

• levees were poorly constructed and dated

• over 50 levees failed, causing widespread flooding in New Orleans

• Over 80% of city flooded, up to 2m in some areas

• failure of levees caused most impacts and deaths

• drowning- 1/3 of all deaths

aftermath

• 1,800 deaths

• drinking water contaminated for 5 months

• 1 million houses damaged, 300,000 destroyed by flood

• 500,000 people homeless

• 230,000 jobs lost

• more than 50,000 pets missing

recovery

• existing socio-economic inequalities created difficulties for some groups

• overwhelming demands, limited resources

• lack of training and capacity

• failure of coordination and communication

• gendered and racialized marginalization

• exclusion from decision-making

controversy and criticism

• criticism towards the slow response at the state- and local level

• failure of federal emergency management agency

pre existing vulnerabilities:

• failure of flood protection due to poor funds, information and construction

• low income communities in New Orleans tend to live in lower lying areas

long term socio-economic impacts: demographic

• 400,000 people permanently displaced

• population of new orleans decreased by 29% between 2005 and 2011

long term socio-economic impacts: employment

• 230,000 jobs lost

employment recovery:

• better for higher income groups

• other groups disadvantaged (women, black communities, those who moved)

long term socio-economic impacts: mental health

5 years after Katrina

• PTSS- post traumatic stress symptoms

• PD- psychological distress

secondary trauma- loss of home/ community

higher earning individuals had less of a risk of developing PTSS/PD

Katrina vs Ida

hurricane defences in New Orleans were rebuilt by 2018 and cost $14.6 billion

hurricane Ida damaged power grids and the water treatment system, but the levees held and didn’t cause floods

Mitigation: Forecasting

• weather satellites

• sea surface temps

• wind speeds

• moisture content in the atmosphere

• scientific aeroplanes

• computer modelling and statistics

• spaghetti plots

climate change and storm events

• 2020 Atlantic hurricane season- 30 storms

• increase in Atlantic tropical storm count and accumulated energy since 1990s

tornadoes def

violently rotating column of air in contact with the ground and a cumulonimbus cloud

tornadoes formation

• moist air ahead of a strong cold front

• duration: minutes to hours

• size: <1km across

• travel a few km

• wind speeds 105-450km/h

tornado classification

Enhanced Fujita Intensity Scale

USA tornadoes: 69% weak, 29% strong, 2% violent

tornado occurrences

USA: 900 per year

UK: 34 per year

Bangladesh: 250 reported 1865-2014

USA tornadoes

In 2017:

• 18 tropical storms (10 hurricanes)

• 1418 confirmed tornadoes

Hurricanes: affect a larger area

Tornadoes: small but frequent

Notable disasters:

Hurricane Katrina (2005) >1000 fatalities

Tri-State Tornado (1925) 695 fatalities

mitigation: tornado forecasting

forecasting is complicated

development of temperature and wind flow patterns

mitigation: tornado safety

know where to go

communication aware of surroundings

education is key

tornado vulnerability

• mobile homes: 82% fatalities

• houses: 87% fatalities