Hazards: Storm Hazards

Question 1

What is a tropical storm?

Answer 1

is a ​low pressure​, spinning storm with high winds and torrential rain.

Question 2

Why is temperature a cause for a tropical storm to develop?

Answer 2

Ocean temperatures must be around ​at least 26 - 27°C ​and at least 50 metres deep. Warm water provides the storm with ​energy​

Question 3

Why is air pressure a cause of a tropical storm?

Answer 3

Must be in areas of unstable air pressure​ ​- usually where areas of high pressure and low pressure meet (​convergence​) - so that warm air rises more readily and clouds can form (this air must also be humid for cloud formation). Warm air rises because it is less dense​ than cold air.

Question 4

Why is wind shear a cause of tropical storms?

Answer 4

Winds must be present for the ​swirling motion​ to form, but not too strong or the storm system will be ​ripped apart​ in the early stages.

Question 5

Why is rotation a cause of tropical storms?

Answer 5

Tropical storms only form around the equator, but no less than ​ ​5° on either side​. The ​Coriolis Effect​ is the effect of the ​Earth’s rotation​ on weather events. The storm spins because the Earth is spinning; but there is ​no Coriolis Effect at the equator​, hence why these storms will only form a certain distance away from it.

Question 6

Why can a trigger also be a cause of a tropical storm?

Answer 6

a pre-existing thunderstorm, a spot of very high sea surface temperature, an area of low pressure and many other factors can act as a ​trigger for a storm to develop, which will only further develop when the ​other conditions are present

Question 7

What’s the development of a tropical storm?

Answer 7

1. Warm, moist air rises​, leaving an area of ​low pressure below​. This causes warm air from surrounding areas of higher pressure to ​move into this low pressure area ​and rise too. Overall, ​warm air is constantly rising ​and accumulating in the atmosphere.
2. warm air rises, cools​, and condenses into​ ​thunderstorm clouds​ and heavy rain, releasing latent heat to further drive uplift and the storm
3. The whole system is spinning due to the ​Coriolis effect​. In southern​ hemi, storms spin ​clockwise​; northern​,​ anticlockwise​.
4. constant additions of energy​ from the warm air causes storm to spin faster and generate higher wind speeds. At ​39mph​ the storm can be classed a ​tropical storm​.

Question 8

How does the tropical storm then mature?

Answer 8

• swirling winds create a central eye (diameter of 30-50km) - an area of subsiding air, light winds, clear skies and high temps. The more intense the storm, the clearer the eye.
• this descending air increases instability by warming as falls.
• Surrounding the eye is the ​eyewall​, the most​ intense and powerful ​area of the storm. Warm, moist air rapidly rises​ here, with extremely​ high winds and torrential rain​. When winds reach ​74 mph​, it becomes a hurricane/cyclone/typhoon.
• wind speeds of 100-150mph are not uncommon

Question 9

What happens when a storm reaches the coast?

Answer 9

• the​ low pressure and high winds​ will cause a large amount of sea water ​taken into the system​ and then released as a high wave called a ​storm surge​.
• When the storm reaches ​land​, it no longer has a ​supply of energy​ (warm, moist air from the sea) and the eye eventually​ collapses​. Heavy rain can persist for days.
• increased frictional drag also slows the storm
• continued movement away from the tropics over the sea bring contact with cooler waters, meaning less energy and a reduction in pressure differences

Question 10

What is the average life span of a tropical storm?

Answer 10

7-14 days

Question 11

What is the global distribution of tropical storm hazards?

Answer 11

• hurricanes usually develop west/southwest of the Atlantic Ocean and the east pacific (around Mexico and the Caribbean Sea) between the equator and the Tropic of Cancer (slight above this though in the Atlantic)- Aug-Oct
• cyclones usually developed within the two tropics north of the Indian Ocean and West of the pacific ocean - June-Dec
• typhoons are west of the pacific ocean between the equator and Tropic of Cancer, although sometimes above it, heading towards Japan - June-Dec

Question 12

How is the magnitude measured for tropical storms?

Answer 12

Measured on the ​Saffir-Simpson Scale ​(A scale of 1-5) based on maximum sustained wind speed and thus power of the storm.
1: 74-95mph - winds produce some damage
2: 96-110mph - extensive damage
3: 111-129mph - devastating damage
4: 130-156mph - catastrophic damage
5: 157mph+ - even more catastrophic damage

Question 13

What is the frequency of tropical storms?

Answer 13

Tropical storms form in the Northern Hemisphere from June-November, and the Southern Hemisphere from November-April. The majority of tropical storms do not develop into strong storms and do not reach land. Tropical storms that are higher magnitude ​and reaching land are thought to be increasing in frequency.
- year with the highest amount of hurricanes in the North Atlantic is 2005 - approx halve being major
- in 1964, all hurricanes that occurred were major
- 1982 was the year with the lowest occurring hurricanes
- the frequency fluctuates, yet the average occurring has increased more recently

Question 14

What is the regularity of tropical storms?

Answer 14

Tropical storms are ​irregular​ because although they occur in the ​same areas​, their path does not follow a set route - the route taken is ​dependent on the storm​ and the climatic conditions.
— they mostly occur from late summer into autumn - over a long period of time there is a degree of symmetry, although this does not mean that in any one year the pattern will be reflective of this

Question 15

What is the predictability of tropical storms?

Answer 15

Tropical storms are fairly predictable, particularly in their geographical locations (restricted in the tropics, yet not close to the equator itself)
- advances in weather prediction computer models means forecasting the initial development of tropical cyclones has improved in recent years
—> each year NOAA publishes a prediction of hurricane activity for the coming season. Uses a number of indicators, such as sea-surface temps, atmospheric conditions and short-term climatic cycles.

Question 16

How are strong winds a storm hazard?

Answer 16

• tropical storms have average wind speeds of over 75mph. In extreme cases, at the eye wall, gusts reach 155mph.
• These can tear off roofs, break windows or damage communication networks
• flying debris (which can also block road networks).
• If power lines fall, result in power cuts and potential electrical fires.
  —> e.g. lots of damage caused by strong winds from Cyclone Winston, Fiji, 2016

Question 17

Why are storm surges a storm hazard?

Answer 17

TSs cause a surge of high water caused by intense low atmospheric pressure (which allows seawater to rise vertically), combined with powerful surface winds (which whip up waves).
- result in coastal flooding as storm surges typically 3-5m higher than normal high tides
—> extreme coastal erosion (with potential to undermine man-made structures), flooding of low-lying land with seawater and/or debris and damage to property. It extreme cases, loss of life.
—> e.g. Hurricanes Katrina, USA 2005, recorded a storm surge of 7.6m, one of the largest ever recorded

Question 18

How is coastal and river flooding a secondary storm impact?

Answer 18

heavy rainfall caused by warm, humid air in TSs can reach levels of over 200mm in a few hours.
- In urban areas, the surface runoff is worse by impermeable surfaces and high density of buildings, meaning runoff often overwhelms drainage systems —> flash flooding.
- Further in land, TSs weaken as moisture and energy supply is cut off without an ocean to fuel it - but sheer volume of rainfall within a river basin can still cause rivers to flood.
—> 2011, Hurricane Irene caused widespread river flooding throughout New Jersey, USA, resulting in evacuation of over 1m people. The damage was estimated at over $1 billion

Question 19

How are landslides a storm hazard?

Answer 19

Up to 90% of landslides each year are caused by heavy rainfall from increased hydrostatic pressure within slope (pore water pressure). This pressure, plus weight of extra water, means theres cohesion and causes the mass movement of material.
- heavy rain with TSs mean landslides are a frequent feature. recent evidence found that sudden release of pressure on ground during landslide may cause earthquakes in tectonically active areas
—> 1998, Hurricane Mitch - one of North Atlantics most powerful tropical storm, triggered multiple landslides that killed 18,000 people.

Question 20

How do we prevent these tropical storms?

Answer 20

• tropical storms cannot be avoided
• however strategies to mitigate climate change could prevent higher category storms.

Question 21

How can we predict tropical storms?

Answer 21

• hurricane warning systems
• computer stimulation like SLOSH
• technology and equipment (leads to warning and evacuations) —> e.g. National Hurricane Warning Centre

Question 22

How can we prepare for tropical storms?

Answer 22

• awareness through education of what to do during a TS
• evacuation plans and training drills (e.g. Project Safeside in Florida) - although very costly
• satellite image tracking to manage the areas at risk
• television broadcasts tracking the storm

Question 23

How can we mitigate tropical storms?

Answer 23

• coastal structures - e.g. sea walls, levees and flood barriers
• hurricane-resilient building designs
• retro-fitting buildings
• insurance (difference between HICs and LICs)
• search and rescue, immediate emergency aid, evacuation (short-term)
  —> LIC example - Dominica, Caribbean - inexpensive but successful example of retrofitting, NGOs trained builders to retrofit homes for less than $500, when hurricane Marilyn hit in 1995, all retrofitted homes withstood the event

Question 24

How can we adapt from tropical storms?

Answer 24

• move away from area at risk
• more flood defences and stronger housing
• land use planning on floodplains, or avoid the sea, etc.

Question 25

Where is Hurricane Katrina located?

Answer 25

southern USA, Aug 2005
Gulf coast states (Louisiana, Mississippi) -HIC

Question 26

What was the nature of Katrina?

Answer 26

• Cat 5 – wind speeds off 280km/hr; weakened to Cat 4 on landfall.
• Massive storm surge (10m high in places)

Question 27

What were the primary impacts of Katrina?

Answer 27

• 80% of city under floodwater. (New Orleans)
• 1,800 fatalities.
• 1 million displaced from homes.
• 110,000 flooded homes with 55,000 of these too damaged to repair.
• Power and water supplies disrupted - 5 million left without power for up to 2 months.
• Key routes out of the city affected (e.g. i10 bridge collapsed)
• Water supplies contaminated.
• 18 schools destroyed and 74 damaged.
• 230,000 jobs lost

Question 28

What were the secondary impacts of Katrina?

Answer 28

• Over $200billion worth of damage – although many businesses were insured.
• Logging industry suffered $5bn loss.
• Very few secondary deaths as clean water, medical care and food delivered to all of affected areas within days.
• Oil rigs and refineries in Gulf area damaged pushing up the price of oil (worldwide impacts felt – e.g. UK petrol reached £1/litre for first time).
• Tourism revenues reduced as famous ‘French Quarter’ severely damaged.
• Looting – many homes and shops looted. National Guard had to be deployed.
• Oil spill pollution from oil refinery damage. (7 million gallons of oil leaked)
• Environmental damage such as sea turtle breeding affected and flooding of salt marshes.

Question 29

What were some of the immediate responses for hurricane Katrina?

Answer 29

• Accurate forecast by NHC led to large-scale evacuation of New Orleans and other preparation
• President Bush declared ‘state of emergency’ 2 days before landfall.
• Mandatory evacuation of New Orleans 19 hours before storm – many felt rushed and left those without private cars behind- Often deprived black communities. 150,000 residents didn’t evacuate.
• Highly-trained/well-equipped services deployed, but found it challenging responding to disaster
  —> Coast Guard rescued more than 33,500 people from floodwaters.
  —> 58,000 National Guard ppl were to deal with storm’s aftermath, with troops from all 50 states.
  —> FEMA paid for hotel costs of 12,000 people/families displaced by Katrina through Feb 7, 2006,
• emergency centres inadequate, e.g. Louisiana Superdome designed for 800, yet 30,000 arrived.
• Financial aid - US Senate authorised $10.5bn in aid in one week. LICs like Afghanistan donated aid.
  • Public donations of $1.8billion from Red Cross.
  • National guard to restore law and order

Question 30

What was some of the long term management for Hurricane Katrina?

Answer 30

• Rehoming displaced residents (75% of these found new homes within 400km) but In 2010, still 260 families living in FEMA- provided trailers in Louisiana and Mississippi.
• Strengthening / replacement of 220 miles of floodwalls and levees ($14bn)
• However, sea level rising means flood walls and levees may not be sufficient in near future! $34bn for rebuilding schools and communities.
• By June 2006, city was hosting conventions and promoting tourism.
• Pop decline: The pop of New Orleans fell from approx 480,000 before Katrina (April 2000) to an estimated 230,000 after Katrina.

Question 31

Why was New Orleans, Louisiana at risk from Katrina?

Answer 31

• Protruding out into Gulf of Mexico.
• New Orleans is naturally low-lying and subsiding land (soil shrinkage due to artificial draining of land), resulting in 50% of city now below sea-level
• Levee failure - levees were ageing and not up to modern standards; 10-40% not replaced.
• Poor black urban residents disproportionally affected by storm.

Question 32

What was the Lower 9th ward for USA for Katrina?

Answer 32

• 98% black and 1⁄2 of residents earning less than $20,000 a year. This was the worst hit area in the whole city.
• Last area to have power and water restored and to be pumped dry of water.
• Long-lasting problems:
  o Rat infestations
  o Abandoned property – many vacant plots
  o Unpaid insurance claims
  o Only 15% of businesses had opened back up by 2007, and 37% by 2015 (compared to 90% city average).

Question 33

Where is Hurricane Matthew located?

Answer 33

Haiti / USA, Oct 2016
- South-western tip of Haiti

Question 34

What was the nature of hurricane Matthew?

Answer 34

• Cat 4 – wind speeds of 230km/hr
• Heavy rainfall (38-64cm) leading to landslides and flooding
• Huge storm surge

Question 35

What were the primary impacts of Matthew?

Answer 35

• 546 people died in Haiti
• 175,500 people displaced, scattered in over 300 temporary shelters.
• 2.1 million people were affected and 1.4 million people were in need of humanitarian assistance, including 800,000 children.
• 20% of all population affected mostly in rural areas
• 80% of Jeremie (main city in SW Haiti) destroyed
• Main roads (N2 route to capital) and vital bridges destroyed and communication lines cut.
• 34 cholera treatment centres were destroyed.
• In the region of Grand’Anse, over 90% of crops destroyed, as well as significant loss of livestock.
• Staple food crops like rice, corn, and beans were wiped out (significant as nearing harvest time).
• Plantations of export crops, including coffee, cocoa, and fruits, destroyed. Experts say it will take at least five years to restore them.

Question 36

What are the secondary impacts of Hurricane Matthew?

Answer 36

• $2.7 billion (equivalent to 32% of Haiti’s GDP)
• Water and sanitation badly hit cholera outbreaks
• Food insecurity and malnutrition as the storm hit the ‘bread basket’ in Southern Haiti (agriculture hit, e.g. farms, seed stocks, irrigation systems) – close to harvest time as bad timing!
  o 800,000 people were at an extreme level of food insecurity.
  o Especially among children, in some of areas, about 30% of children show signs of stunting.

Question 37

What are some of the immediate responses from Matthew?

Answer 37

• Evacuation from Jeremie were ordered for some high-risk areas, including in outlying islands where people were brought to safety by boat.
• US Navy assisted with evacuation and delivering aid
• IGO assistance – e.g. World Bank provided solar lamps to homeless. Also gave cash and seeds to plantation owners to restart business.

Question 38

What was some of the long term management for Matthew?

Answer 38

• Refurbished schools in affected areas.
• Rebuilt N2 road and bridge
• Many NGOs (Red Cross, Action Aid) and IGOs (United Nations) have been working to help Haitian NGOs deal with emergencies. In small emergencies, local officials have been able to manage a disaster response effectively. But the scale of this emergency has overwhelmed their capacity.

Question 39

Why was Haiti at risk for Matthew?

Answer 39

• Warm waters (Atlantic Ocean) acts as a ‘birth place’ for tropical storms
• Few large pieces of land to slow them down in the Caribbean.
• Preparedness is difficult as the country is fragile and vulnerable to disasters. Haiti was still recovering from a series of hazards:
  —> Devastating 2008 hurricane season (4 consecutive Faye, Gustav, Hanna, Ike - 15% of GDP; 1,000 deaths
  —> 2010 – Earthquake – 120% of GDP, 230,000 died
  —> 2021 – 7.2Mg quake; 2,200 died
• Infrastructure is poor in rural areas, making it difficult for the local population to prepare for such a large-scale disaster
• Generally ill-prepared – only 90,000 storm shelter capacity in Southern Haiti in order to protect millions.
• Many residents unaware – no warning, some fishermen even still going out to sea as storm approached.
  Other factors to consider:
  • Poverty and poor housing quality
  • Lack of insurance
  • Rural-urban migration leading to rapid growth of slums
  • Unstable and corrupt government - lack of preparedness and lack of response (e.g. left dead bodies lying in the water; poor building code enforcement; no land use planning)

Question 40

How is Haiti trying to reduce its vulnerability?

Answer 40

After the January 2010 earthquake, reducing vulnerability, improving emergency preparedness and response and understanding risks became key themes for Haiti’s government and the international community.
World bank gave $60 million to finance the disaster management project

Question 41

How is Haiti mitigating hazards now?

Answer 41

Early warning systems were put in place

Question 42

How is Haiti preparing for Hazards now?

Answer 42

• Data generated for risk assessment using earth observation, remote sensing technology and hydrological risk models
• Health and Education ministries strengthened their disaster management plans
• Training in disaster management delivered to 127 officials

Question 43

How is Haiti going to response to future hazards now?

Answer 43

• Emergency evacuation
• Emergency shelter management
• 7 emergency shelters established in rural areas

Question 44

How is Haiti planning on recovering from future hazards now?

Answer 44

• Transport project that used multi-hazard maps to create reliable engineering solutions for post-disaster reconstruction
• Men and women trained as skilled labourers to to fix damage and to create job opportunities in mainly poor areas