Hurricane NASA Typhoon NOAA - PowerPoint Presentation

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Hurricane

NASA

Typhoon

NOAA

Cyclone

NASA

What is the name of the meteorological phenomenon that means the same as all of these?

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Tropical Cyclones

06/12/2020

Learning Objectives:What conditions lead to tropical cyclones?In what way do they represent a hazard to people?

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What are tropical cyclones?

Where do they form?

What ingredients are required for their formation?

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What is a tropical cyclone?

A tropical cyclone is a low pressure system over tropical or sub-tropical waters, with organised convection (i.e. thunderstorm activity) and winds at low levels circulating either anti-clockwise (in the N.hemisphere) or clockwise (S.hemisphere). It has an average diameter of ~500km and height ~15km.

Where does a tropical cyclone form?

In the tropics!

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What ingredients are required for their formation?

Warm water (>26.5oC)to a depth of at least 50m.

An existing atmospheric disturbance (e.g. a weak low pressure system)Must be at least 500km (300miles) north or south of the equator so that the Coriolis force is strong enough to aid their development.

Small wind shear (only small change in wind speed throughout the atmosphere) so the developing system does not get ‘torn apart’.

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What is the difference between a typhoon, hurricane and a cyclone?

The region in which they form

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World map showing the track of all known tropical cyclones. Note how none have formed in close proximity to the equator. Add the names of tropical cyclones in each region to your world map.

NOAA

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Naming conventions of tropical cyclones for world regions

"hurricane" (the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean east of 160E)

"typhoon" (the Northwest Pacific Ocean west of the dateline)

"severe tropical cyclone" (the Southwest Pacific Ocean west of 160E or Southeast Indian Ocean east of 90E)

"severe cyclonic storm" (the North Indian Ocean) "tropical cyclone"

(the Southwest Indian Ocean)

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Hurricanes

Typhoons

Severe tropical cyclone

Tropical cyclone

Severe cyclonic storm

NOAA

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14.9 hurricanes per year 1851-2006 average

16.9 typhoons per year 1959-2005 average

Worldwide Tropical Cyclone Statistics

Named systems – Yellow

Hurricanes – Green

Category 3 or greater - Red

Date of storm formation in the Atlantic.

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This satellite image clearly shows the intertropical convergence zone (ITCZ). However it is broken into discrete clusters of thunderstorms. These are known as ‘waves’. Forecasters watch these areas for signs of tropical cyclogenesis.

NASA

ITCZ

Wave disturbance

Tropical Cyclone Formation

(Tropical Cyclogenesis)

NASA

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Slide12

Tropical cyclones originate from a humble thunderstorm!

These require converging air at the surface i.e. a low pressure system such as a wave on the ITCZ. These have anticlockwise winds (in the N.hemisphere) and so only form 500km either side of the equator (between 5

o and 20

o) where the Coriolis ‘force’ is strong enough.

Converging air in a low pressure forming thunderstorms

NOAA - 8

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If a cold upper-level trough from mid-latitudes moves into the area of thunderstorm development then the air becomes convectively very unstable and the thunderstorms will start to grow very large.

Upper, cold low pressure

Warm, humid air

Warm sea

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As latent heat is released by the condensing water vapour, the cold air aloft warms and increases in pressure.

High pressure

Low pressure

Diverging (moving apart) air aloft

NWS - 9

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Latent heat experiment

Bring 50ml of water to the boil. Time how long it takes for all of this water to evaporate.The total amount of energy supplied to the water can be calculated from:

Energy = Time x 9800J/sThe latent heat of water can be found from:L=Q/m

Where Q = Energy supplied and m= mass of water used in kg.

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Latent heat experiment

You should find L=2.3million Joules/kgThis tells you how much heat energy is released when 1kg of water vapour condenses into liquid water in a tropical storm.

On average 1,000,000,000kg of water condense per second in a tropical cyclone. Calculate how much energy is released per second in a tropical cyclone.

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Answer:

2.3x10

15 J/s

This amount of energy is the equivalent of a 10 megaton nuclear bomb exploding every 20 minutes!

A 10.4 Megaton nuclear bomb test

US Department of Energy - 10

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The diverging air aloft ‘sucks’ air up from the surface and with continued convection causes the surface low pressure to drop further. Surface winds now increase and begin to spiral inwards. This make the sea rougher which makes the winds turn further to the centre of the developing storm.

Blue arrows

– Pressure gradient force (pgf)Red arrows

- Coriolis forceBlack arrows – Direction of wind

As the surface friction increases, the wind slows and so the Coriolis ‘force’ decreases. The pgf remains constant and so the winds spiral into the centre of the surface low.

L

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The feedback mechanism:

-Air now reaching centre is warm and moisture laden after travelling over choppy warm seas.-This adds extra energy in the form of latent heat to the thunderstorms, increasing their rate of growthThe surface pressure drops further

Surface winds increaseSea becomes more choppyExtra warmth and moisture transferred to the air

And so on.When 35-64 knot wind speed is reached we call it a tropical storm and when it increases to 65 knots we call it a tropical cyclone.

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Task:

Rearrange the statements to show the process of tropical cyclogenesis.Or

Rearrange the pictures to show the stages of tropical cyclogenesis. Label them to provide an explanation of the processes involved.

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H

L

Eye of storm = Calm light winds

>15km

~500km

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Eye – Centre of storm. Calm conditions. Surrounded by most violent winds up to ~200mph under the eye wall

Picture taken by the NOAA Hurricane hunter aircraft

which monitors hurricanes which are threatening the US coast.

Hurricane Luis eye video satellite image

Hurricane Katrina

NASA -

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What factors stop the tropical growing to the size of the Earth!?

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This growth will continue until:

Moisture is cut off – i.e. Cyclone moves over landHeat is cut off – i.e. Cyclone moves too far north or south

Wind shear (wind strength increasing with height) increases – This tears the cyclone apart – Common near Hawaii. Video

Cyclone becomes ‘full’ of thunderstorms so latent heat release is limited.

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How do tropical cyclones pose a danger to people?

NASA - 2

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1.) Storm surge (up to 5m) due to a) low pressure causing local rises in sea levels and b) wind pushing water along.

90% of deaths in tropical cyclones are due to flooding.

Relative effects of pressure surge and wind-driven surge.

Video

Wikipedia - 13

NASA - 12

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2.) Wind damage

3.) Flying debris4.) Damage to infrastructure e.g. Roads and electricity supplies.

Video of flying debris

Damage from Hurricane Katrina

FEMA News Photo - 14

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What are the social, economic and environmental issues associated with tropical cyclones?

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Social

Deaths & injuriesDiseaseDisruption to all events

e.g. School, work, sportEnsuing or deepened poverty

EconomicCleanup billDamage to buildings & infrastructure

Loss of businessesLoss of tourism

FEMA News Photo - Davie, Florida 2005

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Environmental

Destruction of habitatsSewage leaksChemical leaks

New Orleans, Louisiana 2005

US Coast Guard - 16

US Coast Guard

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Hurricanes are rated on the Saffir Simpson Scale –

Link to official scale

Animation with interactive Saffir-Simpson Scale

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Case Studies

Hurricane Andrew:

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th August 1992Bahamas & Florida

Category 5Max average 1 min wind speed = 175mph

Lowest pressure = 922mbarStorm surge of 5.2m67 deaths

$41.1 billion (adjusted to 2010 rates)Over 1.1 million people evacuated and 1500 troops deployed to prevent looting.

Video

NOAA - 18

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Case Studies

Hurricane Mitch:

29

th October 1998Honduras, Nicaragua, Mexico,

Florida(flooding also in Central America)Category 5Max average 1 min wind speed = 180mph

Lowest pressure = 905mbarStorm surge of 3.7m in Honduras

11,000 deaths mainly in Central America due to flooding and mudslides – Up to 1500mm (5 feet) of rain fell! $8 billion (adjusted to 2010 rates)

Honduras evacuated 45,00 people and put armed forces on standby. 100,000 later evacuated.

Video

NOAA - 19

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Case Studies

Hurricane Katrina:

29

th August 2005Bahamas, Florida Louisiana

Category 5 (3 at landfall in Louisiana)Max average 1 min wind speed = 175mph

Lowest pressure = 902mbarStorm surge of 4.3m in Louisiana1836 deaths

$90.1 billion (adjusted to 2010 rates)State of emergency declared two days in advance. Unprecedented text used in

weather statement to convey likely devastation of storm. 1.2 million people ordered to leave homes.

Video

NOAA - 20

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Case Studies

Super Typhoon Saomai:

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th August 2006Zhejiang Province, China

Category 5 (4 at landfall)Max average 1 min wind speed = 160mph

Lowest pressure = 925mbarStorm surge of 4.0m458 deaths

$2.7 billion (adjusted to 2010 rates)50,000 houses destroyed; 380 km2

of farmland flooded.1.6 million people evacuated. 20,000 soldiers deployed to help in the cleanup and rescue efforts.

Video

NOAA - 21

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Case Studies

Cyclone Larry:

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th March 2006Queensland, Australia.

Category 5 (4 at landfall)Max average 1 min wind speed = 135mph

Lowest pressure = 940mbarStorm surge of 2.3m1 indirect death

$920 million (adjusted to 2010 rates)Most banana crops destroyed, many houses in the direct path were damaged (including 99% in Silkwood).

Video

NASA

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Homework

– DueResearch two tropical cyclones in different parts of the world, gathering data on:Meteorological statistics

PreparationsImpactsResponses to the cyclone including rebuilding plans and progress.

Extension -Discuss how future development planning could incorporate tropical storm preparedness designs.

- OR argue whether we should continue building in these areas at all.

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Role play! A major hurricane is heading towards the southern coast of the US where you live. Act as if you were:

-Meteorologist advising authorities

-Governor of state-Emergency services on the ground-Homeowner

-Business owner-Storm chaser!Imagine the views you would have as each of these characters and how you would argue your case.

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Sources:

NOAA - http://www.katrina.noaa.gov/satellite/images/katrina-08-29-2005-1345z2.jpg

Image Science and Analysis Laboratory, NASA-Johnson Space Center. "The Gateway to Astronaut Photography of Earth”.

http://eol.jsc.nasa.gov/sseop/images/EO/highres/ISS008/ISS008-E-19646.JPG

NOAA - http://www.nnvl.noaa.gov/members/images/109687.jpgWikipedia Commons -

http://en.wikipedia.org/wiki/File:Global_tropical_cyclone_tracks-edit2.jpg

NHC NOAA - http://www.nhc.noaa.gov/gifs/peakofseason.gif

NHC NOAA - http://www.nhc.noaa.gov/gifs/atlhist_lowres.gif

NASA - http://disc.sci.gsfc.nasa.gov/oceancolor/additional/science-focus/ocean-color/science_focus.shtml/convergence.shtml

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Sources:

NWS - http://www.srh.weather.gov/jetstream/tstorms/life.htm

NWS - http://www.srh.noaa.gov/jetstream//tropics/tc_structure.htm

US Department of Energy - http://www.cfo.doe.gov/me70/manhattan/early_bomb_design.htm

NOAA - http://www.srh.noaa.gov/lzk/imgviewer2.php?pic=katrinaeye082805

NASA -

http://earthobservatory.nasa.gov/Features/Hurricanes/Images/storm_surge.gifEmmanuel.boutet – Wikipedia -

http://en.wikipedia.org/wiki/File:Surge-en.svg

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Sources:

FEMA News Photo - http://www.photolibrary.fema.gov/photodata/original/14801.jpg

FEMA News Photo - http://www.photolibrary.fema.gov/photodata/original/14365.jpg

US Coast Guard - http://www.uscg.mil/history/katrina/katrinaoralhistoryindex.asp

Wikipedia http://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_Hurricane_Scale

NOAA-

http://www.publicaffairs.noaa.gov/photos/1992andy1.gifNOAA -

http://www.ncdc.noaa.gov/img/olimages/hurr-mitch-19981027-n15.gif

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Sources:

NOAA - http://www.katrina.noaa.gov/satellite/images/katrina-08-29-2005-1315z2.jpg

NOAA - http://www.nnvl.noaa.gov/cgi-bin/index.cgi?page=items&ser=111116

NASA - http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=16268&oldid=13421