tropical cyclones overview

Key Facts about Cyclones

FactFact Your GuessYour Guess Actual Actual AnswerAnswer

Av. diameter (km)Av. diameter (km)

Av. height (km)Av. height (km)

Av. # of Cyclones a Av. # of Cyclones a yearyear

Av. lifespanAv. lifespan

Cyclone season in Cyclone season in the South Pacificthe South Pacific

Minimum wind speed Minimum wind speed (km/hr)(km/hr)

Max. wind speedMax. wind speed

Av. speed across the Av. speed across the groundground

Most rainfall Most rainfall recorded in 24hrs recorded in 24hrs (mm)(mm)

480km

Nov-MarchNov-March

1 week1 week

90 km/hr90 km/hr

280+ 280+ km/hrkm/hr

1825mm1825mm Auckland I year = Auckland I year = 12401240

4545

15km Everest = 8.8km

16-24 16-24 km/hrkm/hr

Auckland-Cape Reinga = 436

AREAS OF CYCLONE FORMATION

GLOBAL AIR MOVEMENT

http://www.youtube.com/watch?v=aAIDJbKb-xI&feature=related

DESERTS OF THE WORLD

A Recipe for a CycloneA Recipe for a CycloneA large

expanse of ocean

Intense heat of the sun at

tropical latitudes

Jet stream between 10°-30° latitude

Coriolis force (too weak near

the equator)

These 2 ‘ingredients’ mix together to create an ocean heated to at

least 26.5°C, and it provides latent heat

(energy) from condensation which

adds power

Tropical cyclones

(start between 5°-15° latitude)

+ ++

AREAS OF CYCLONE FORMATION

Processes – Step 1Processes – Step 1

All cyclones follow a similar process when forming regardless of where they are located around the world.

Processes – Step 2Processes – Step 2 All start near the equator as areas of low pressure. This area is known as the Inter Tropical Convergence Zone (ITCZ), where winds from the Northern and Southern Hemispheres meet.

Processes – Step 3Processes – Step 3 Because of the location near the equator, temperatures are hot, and the air over the water is forced to rise. The heat of the sun warms the ocean water to a temperature of at least 26.5oC, as this causes some of the sea water to evaporate.

Processes – Step 4Processes – Step 4 This evaporating of water mixes together with the rising air to form a mass of warm, wet air which is moving upwards.

Processes – Step 5Processes – Step 5 In the Southern hemisphere this rising column of air is caused to spin clockwise by the Coriolis effect, the effect of the earth’s rotation (remember in the northern hemisphere it spins anti-clockwise). The tropical cyclone at this stage is a spinning mass of warm, moist rising air.

Processes – Step 6Processes – Step 6

As it continues to rise air from surrounding areas is sucked in below it, adding more moist, hot air.

Processes – Step 7Processes – Step 7

As this parcel of air rises, it cools, condenses and forms into large, dark cumulonimbus rain clouds.

Processes – Step 8Processes – Step 8 Jet streams are high speed air currents which circle the earth between 10o and 30o latitude at high altitudes. The jet streams cause the air movement in the forming cyclone to increase in speed as they suck the air further upwards (like a vacuum).

Processes – Step 9Processes – Step 9 More air from surrounding areas rushes into the intense low pressure centre which has been formed, and the process is repeated. The latent heat generated by condensation warms the air further and keeps the winds swirling.

Processes – Step 10Processes – Step 10 The spiral of air and heavy rain that is produced by this process moves across the ocean with the prevailing winds, causing destruction in its path.

Processes – Step 11Processes – Step 11

The fully mature tropical cyclone can be several hundreds of kilometres in diameter.

Processes – Step 12Processes – Step 12 At its centre is the eye, an area of calm, dry, sunny weather, formed by some of the air being forced downwards. As the eye of the cyclone passes over a place conditions will therefore change for a short period of time, with a lull in the heavy rainfall and winds.

Processes – Step 13Processes – Step 13 In order for a cyclone to continue on its path, it needs constant fuelling with heat and moisture; if its supply is cut off the cyclone will fade and die. Typically this occurs when the cyclone either passes over a large land mass or reaches lower latitudes where temperatures are cooler.

http://www.youtube.com/watch?v=HJydFJORWf4&feature=related

Check Point QuestionsCheck Point Questions1. What causes wind?2. Why is the equator hotter than either pole?3. Which way does a cyclone spin in the Southern

Hemisphere?4. Name the four things that need to be present for a

cyclone to form.5. What is the ITCZ?6. Why do clouds form?7. What is latent heat and how does it power a cyclone?8. How many categories of cyclone are there and which

is the strongest?9. Why don’t cyclones form close to New Zealand?10.What causes a cyclone to spin?11.Which country is being hit by a cyclone right now?12.Where can you find jet streams?13.What is the latitude where cyclones start?

PERCY – KEY FACTS FOR USE IN PROCESSES PARAGRAPH

Formed: February 24th at 9oS in the Pacific near the Tuvalu IslandsMax. Wind Speed: 260kphLife-span: 8 daysMax. Size: Category 5 (March 2nd)Pressure: 900 millibars

Cyclone Formation By Cyclone Formation By NumbersNumbers

26.5

5-15

10-30

45

90

480

15the latitude range north and south within which cyclones can form

The minimum temperature the ocean has to be for cyclones to be able to start

The height of the average cyclone (km)

the average number of cyclones formed around the world each year

the latitude north and south where the jet stream operates

the minimum wind speed for a cyclone (km/hr)

The average diameter of a cyclone (km)

FQ2: Effects on the Natural Environment

AGENTS OF DESTRUCTION!!

VIOLENT winds

Storm SurgeHeavy Rainfall

High Waves

VIOLENT winds - FACTSThe eye wall has the strongest winds in a cyclone

Wind gusts have been recorded up to 360kmh

VIOLENT winds – TYPES OF DAMAGE1. Destroy vegetation – uprooted, leaves

torn off

VIOLENT winds – TYPES OF DAMAGE2. Salt burns on vegetation – crystallized

salt from the ocean picked up by the wind and driven into plants

VIOLENT winds – TYPES OF DAMAGE3. Erosion – mainly of beaches and exposed

soil

Heavy Rainfall - Facts

Rain can fall for many hours before the full force of the cyclone hits.

Common for 300mm to fall in a couple of hours

Heavy Rainfall – Types of Damage

1. Flooding of rivers, impacting inland areas

Heavy Rainfall – Types of Damage

2. Deposition of mud, silt and debris from flooded rivers

Heavy Rainfall – Types of Damage

3. Erosion of river banks after flooding

Heavy Rainfall – Types of Damage

4. Landslides caused by waterlogged soil

This is the rise in sea level along a shore caused by strong winds and the low pressure of a cyclone.

Storm Surge - Facts

Storm surges can increase the sea level by over 5.6 meters during a Category 5 cyclone

Storm Surge – Types of Damage

1. Flooding of coastal areas

Storm Surge – Types of Damage

2. Erosion of coastal areas, including beaches

Hurricane Isabel (2003)

Storm Surge – Types of Damage

3. Deposition of sand, stones and logs

Storm Surge – Types of Damage

4. Contamination of fresh water with salt water, especially in aquifers

Storm Surge – Types of Damage

5. Salinization of the soil – sea water evaporates after flooding, leaving salt in the soil and ruining vegetation (and allows more erosion to occur later)

Caused by strong winds out at sea – are steep, have no shape and always breaking

High Waves - Facts

Waves can get up to 14 meters high in the worst cyclones

1. Coastal flooding

2. Erosion of coastal features, including coral reefs

3. Deposition of sand, boulders, logs etc

High Waves - Types of Damage

Focusing Question 1: Cyclone Processes

1. What is found at latitudes 10-30o?

2. What causes the extreme low pressure of cyclones?

3. At what latitudes do cyclones form?

4. What are the other two names used for cyclones around the world?

5. What are the two things that happen to air as it rises?

6. Where are the winds and rain the hardest in a cyclone?

7. Which way does a cyclone spin in the Southern Hemisphere?

8. How do clouds form?

9. What is the temperature the ocean has to be before the water starts evaporating?

10.Where does latent heat come from?

The Basics of Cyclone Percy

1. What year did Percy occur?

2. What day did the tropical depression that lead to Percy first form?

3. On what day did it reach Category 5?

4. At what latitude did it form?

5. What three countries or territories did it affect the most?

6. In what order where they hit?

7. What are the three islands that make up Tokelau?

8. What type of islands were affected by Percy?

9. What is the main activity on all the islands affected by Percy?

Focusing Question 2: Effects on the Land

1. What are the four agents of destruction in a cyclone?

2. What is salinization?

3. What is a storm surge and what causes it?

4. What is an aquifer and how can it be affected by a cyclone?

5. What was the maximum wind speed of Percy?

6. How high were the floods caused by the storm surge?

7. Where were the storm surges the highest?

8. What happened on the western sides of Nukunono and Fakaofa?

9. What was dumped into lagoons?

10.Where did landslides occur?

11.What were the three types of trees damaged by the winds?

Focusing Question 3: Social and Economic Effects of Cyclones

1. What were broken on the western side of Tokelau’s atolls?

2. Where was overall damage the greatest?

3. How many people died in the cyclone?

4. In Tokelau, what percentage of the pigs were drowned?

5. What percentage of buildings needed repair on Pukapuka?

6. What was damaged between Atafu to the other Tokelau Islands?

7. Who was the only serious casualty?

8. What happened to the homeless people in the islands?

9. List three types of mess that had to be cleaned up in the islands.

10.What important food source was flooded?

Focusing Question 4: How People Can Increase or Decrease the Effects of Cyclones?

1. Who detected the storm?

2. Who warned the islands about Percy?

3. What were three things the Islanders did as part of an emergency plan?

4. Why were supplies low on the islands before Percy struck?

5. What was the priority for the taro plants after the cyclone?

6. Which three places had international aid channelled through them?

7. What was the first priority for the islands after Percy had stuck?

8. How long did it take for the first supply ships to arrive?

9. What saved many lives during Cyclone Percy?

10.Name three things that were donated to the islands, not including money, after the cyclone.

Focusing Question 3: Social and Economic Effects of Cyclones

“The social effects of an extreme natural event relate to people, their families and personal lives.

The economic effects relate to people earning money, creating wealth and spending wealth.”

Focusing Question 4: How Can People Increase or Decrease the Effects of Cyclones?

Two main components:

BEFORE the cyclone and AFTER the cyclone

BEFORE the cyclone hits.

1. Where People Live and Work (Zoning Regulations)

A lot of people, businesses (e.g. tourist resorts) and economic resources (e.g. crops) on the coast will ___________the effect of cyclones.

If the government limits the number of people who can live and work near areas in danger from cyclones, this will ____________ the effects.

BEFORE the cyclone hits.

2. Building Codes and Standards

Poorly made buildings will _______________ the effect of cyclones.

Buildings that are created to withstand high winds will ____________ the effect of cyclones.

The government can control this with building codes.

BEFORE the cyclone hits.

3. Specific Area Defenses

Specific structures built to protect land and property from wind, rain, waves and storm surges will ______________ the effect of cyclones.

BEFORE the cyclone hits.

4. Warning System

Being able to detect a cyclone early and warn people will ____________ the effect of cyclones.

BEFORE the cyclone hits.

5. Emergency Plan

A clear set of instructions for both the government and citizens to follow will _______________ the effect of cyclones.

Not having a plan, or not educating the population about the plan, will ____________ the effect of cyclones.

BEFORE the cyclone hits.

6. Insurance

Not having insurance for personal property will _______________ the effect of cyclones.

BEFORE the cyclone hits.

7. Population Density and Urbanization

A high population density (for example, a city) will _____________ the effect of cyclones.

BEFORE the cyclone hits.

8. Infrastructure quality

Poor transport, communication, waste management and government systems will __________________ the effect of cyclones

BEFORE the cyclone hits.

9. Crop management

Harvesting before cyclone season will _______________ the effect of cyclones.

Having a variety of crops will ________________ the effect of cyclones.

AFTER the cyclone hits.

1. Immediate response

Emergency aid (medical, food, water, clothing and shelter), transportation of people and the search for survivors will ______________ the effect of cyclones.

AFTER the cyclone hits.

2. Long-term Relief

Temporary housing, food rations and the clean-up of debris and waste can ____________________ the effect of cyclones.

AFTER the cyclone hits.

3. Rehabilitation

Replacement of homes and buildings; providing plant material to regrow crops; roads, bridges and ports fixed; electricity, water, sewage and communication systems repaired – all of these will _______________ the effect of the cyclone.

AFTER the cyclone hits.

4. International Aid

Aid such as cash, medical supplies, food and machinery, as well as donated labour and expertise – these all _____________ the effect of cyclones.

FQ4: How people increased or decreased the effects of PercyPukapuka has an unsealed airstrip only suitable for small planes.

Volunteer labour came from Samoa, Cook Islands and the French Armed Forces

Swamp taro is grown away from the coast.

Many homes were already cyclone-proof due to recommendations after previous cyclones.

Homeless people moved in with neighbours or camped in churches or schools.

Islanders turned off power supplies, crops were picked, food and water was stored, houses, boats and animals were secured and people moved to stronger buildings.

The first supply ships arrived a week after the cyclone.

People dived into floodwater to rescue taro shoots before they rotted.

All islands have satellite, radio and telephone links, but they depend on solar power or diesel generators

RSMC in Fiji detected the depression and estimated its path. This was passed on to the APCEDI in Fiji who contacted the islands in danger.

The first priority after the cyclone was health and safety. Medical officers gave aid.

Money and goods came from Tokelau and Pukapuka communities in Raratonga and NZ, as well as the Australia and NZ Governments, the Red Cross and the United Nations.

Writing a ParagraphDescribe ONE action that people could take to reduce the effect of your extreme natural event.

Key Idea: Restate the question and add your choice

Explanation: Describe what your choice is, how it works, what it can include, and what effect it can have on other thingsExample: Use specific information (names, places, dates, numbers) from your case study and explain how this influenced other factorsDiagram: If possible, add a diagram to clarify anything you have written above.

Writing a Paragraph – Model AnswerDescribe ONE action that people could take to reduce the effect

of your extreme natural event.

One action that people can take to reduce the effect of cyclones is to establish an effective warning system. This could include satellite imagery to detect the formation of storms that could develop into cyclones, along with a reliable communication system to pass warnings between widely separated islands. By receiving early warnings, people could enact an emergency plan and local authorities could evacuate areas in danger. During Cyclone Percy, a meteorological centre in Fiji detected the original tropical storm and passed this information on to an disaster information centre in the same country, who then relayed the information to the Tokelau and Cook Islands that were in the projected path of Percy. The islands all had communication systems that ran on solar panels and diesel, so they received the warnings and were able to make preparations like returning to their villages, storing food and water safely, securing boats and livestock and turning off the power supply. This consequence of this early warning and subsequent emergency plan is that the damage was minimized on the islands. Indeed, there were no fatalities in the cyclone.

CASE STUDY 2: HURRICANE KATRINA

Hurricane Katrina: Key Facts

Formed: August 23rd, 2005 in the North Atlantic Ocean

Countries affected: Cuba, USA

U.S. States most affected: Florida, Mississippi, Louisiana

City most affected: New Orleans (Louisiana)

Peak strength: Category 5, August 28th – (six strongest ever recorded in the Atlantic)

Lowest pressure: 902mbar (Percy was 900; record low is 870, average air pressure at sea level is 1013, record high is 1048)

Highest winds: 280kmh

Damage: Costliest natural disaster in US history

Hurricane Katrina: Mapping

Copy the track of Hurricane Katrina on to the map from page 114.

Locate and label the following states: Alabama, Florida, Georgia, Kentucky, Louisiana, Mississippi, Ohio (use an atlas)

Use choropleth mapping to display the following death statistics in Katrina:

Alabama 2, Florida 14, Georgia 2, Kentucky 1, Louisiana 1577, Mississippi 238, Ohio 2

Label the latitude and longitude lines.

Locate and label New Orleans

CYCLONES: POP ASSESSMENT

Answer these 10 questions on your paper. You have the rest of the period to complete it and hand it in to me.

1. Name your two case studies, and when and where they took place2. Describe the processes that lead to the formation of your extreme

natural event.3. List the four agents of destruction in your extreme natural event.4. Write a paragraph describing TWO effects on the land caused by

any of these agents of destruction, using evidence from at least one case study.

5. List FIVE social effects of your extreme natural event.6. Write a paragraph describing ONE of these social effects of your

extreme natural event, using evidence from at least one case study.

7. List THREE economic effects of your extreme natural event.8. Write a paragraph describing ONE of these economic effects of

your extreme natural event, using evidence from at least one case study.

9. Write a paragraph describing how people can minimize the effects of your extreme natural event BEFORE it occurs, using evidence from at least one case study.

10. Write a paragraph describing how people can minimize the effects of your extreme natural event AFTER it occurs, using evidence from at least one case study.

Complete this structured paragraph in your book with your own information:

There are many ways people can reduce the effects of cyclones before they happen. One of these is to…….

This involves……………

This reduces the effects of a cyclone by……..

For example, in Cyclone Percy, ……………………………..

However, in Hurricane Katrina……………………….

Advice for Revision1. Make sure you have all the notes and information! This is the main purpose of today. Go through the checklist and see what you are missing.2. Draw up a revision plan. For example, do “Processes”

on Friday, “Effects on the Environment” on Saturday etc. This way, you can keep track of what you have gone over and not be swamped with all the information at once. 3. Practice drawing diagrams and maps. They will be

invaluable in all parts of the test. 4. Find new ways to remember the important facts. For example, make a list of numbers related to Hurricane Katrina (29, 80, 1577, 902, 95 etc) and every day go over them and try to recall what they represent. At the start of the exam, quickly write these numbers down on the back of the paper and refer to them.

OR make a list from A to Z of important events in Cyclone Percy (A is for airstrip – Pukapuka only had an unsealed airstrip, which made it difficult for supplies to be delivered to the island. B is for bridges – several were damaged during the cyclone…etc)

Extreme Natural Events (Anderson)Cyclone Percy (pg 63-81)Processes (pg 65-67)

Natural Hazards (Hensman et al)Processes (pg 104-106)

Geography NCEA Level One (Chittenden)Processes (pg 7-11)

Geography on the Edge (Peat and Lockyer)Processes (pg 98-101)Hurricane Katrina (pg 114-119)

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