BFRB – Pages 125 - 129

Today, you will learn…Today, you will learn…•What hurricanes and What hurricanes and tornadoes aretornadoes are

•How they formHow they form•How society should How society should prepare for them to reduce prepare for them to reduce loss of life and property loss of life and property damagedamage

• They are They are funnelfunnel shaped columns of shaped columns of spiraling winds that extend down to the spiraling winds that extend down to the ground from the base (bottom) of a ground from the base (bottom) of a cloudcloud

• The visible funnel is made by water The visible funnel is made by water droplets (clouds), dust and debris droplets (clouds), dust and debris getting caught up in the wind and getting caught up in the wind and spiraling around in the funnel They spiraling around in the funnel They usually last about usually last about 1010 minutes or less but minutes or less but can sometimes last for hours.can sometimes last for hours.

• Tornadoes are rated on the Tornadoes are rated on the FujitaFujita scale scale F0 (weakest) – F6 (severe)F0 (weakest) – F6 (severe)

• An F6 is very rare, and can have wind An F6 is very rare, and can have wind speeds up to speeds up to 318 mph318 mph

TornadoesTornadoes – Some Facts…

TornadoesTornadoes – How They Form

• Form from Form from very powerful very powerful thunderstormsthunderstorms (cumulonimbus clouds) (cumulonimbus clouds)

• In the US, they are most common in In the US, they are most common in springspring and and early summerearly summer because of because of coldcold temperatures in Canada and temperatures in Canada and warmerwarmer temperatures in the Gulf of temperatures in the Gulf of Mexico.Mexico.

• Tornadoes can occur anywhere in the Tornadoes can occur anywhere in the US but most of them occur in the US but most of them occur in the centercenter of the country in an area called of the country in an area called ““tornado alleytornado alley””

This area of the US is known as “tornado alley”

Why do most tornadoes in the US happen here in “tornado alley”?

This is a maritime tropical air mass “mT”

Cool, dry, dense air comes down from Canada

This is a continental polar air mass “cP”

Warm, moist, less dense air comes up from the Gulf of Mexico

The 2 air masses meet at a front and the cool dense air pushes the warm less dense air up very quickly creating a horizontal tube of swirling air – think of a roll of toilet paper.

Then, this horizontal tube of swirling air may be tilted toward the vertical by some sudden updrafts of air.

This turns the spinning tube of air into a vertical funnel cloud which eventually builds strength and speed and turns into a tornado

Here is an animation….http://www.britannica.com/thunderstorms_tornadoes/ocliwea124v4.html

How does the tornado funnel form?

• Tornadoes are especially Tornadoes are especially dangerous because it is so dangerous because it is so difficult difficult toto predict predict where and when they where and when they will formwill form

• Damage is usually along a Damage is usually along a narrow narrow path path where the tornado traveledwhere the tornado traveled

• Most fatalities (deaths) are caused Most fatalities (deaths) are caused by by flying debrisflying debris

• High winds cause High winds cause severe property severe property damagedamage

TornadoesTornadoes – How they cause damage…

And now, some very And now, some very cool pictures of cool pictures of

tornadoes…tornadoes…

NEW YORK TORNADOES!NEW YORK TORNADOES!

Tornadoes will Tornadoes will pick up dust and pick up dust and debris from the debris from the ground when ground when they “touch they “touch down” – this down” – this creates a wider creates a wider swirl at the swirl at the bottom of the bottom of the tornadotornado

Yes, tornadoes are very Yes, tornadoes are very cool and interesting…cool and interesting…

But, they can also be very But, they can also be very deadly to people and deadly to people and

costly to the economy. costly to the economy. What should people do to What should people do to

prevent loss of life and prevent loss of life and damage to structures? damage to structures?

A Government or Public A Government or Public emergency preparedness emergency preparedness plan for tornadoes should plan for tornadoes should

consist of… consist of… •Warning system – TV/Radio/Internet/Sirens

•Emergency shelters for people made homeless by the storm

•Building/Construction codes that minimize damage – ex – no mobile homes or weakly built structures

A Family/Personal emergency A Family/Personal emergency preparedness plan for preparedness plan for

tornadoes should consist tornadoes should consist of… of… •Where to go?

Basement/storm cellar or an interior room with no windows like a bathroom or closet

•What to have? Bottled water/canned food/battery powered radio/flashlight

•What to do? Stay put until they announce that the danger has passed

Hurricanes – How they Hurricanes – How they formform • Huge Huge tropical low pressure systemstropical low pressure systems that get that get

their energy from the tremendous amount of their energy from the tremendous amount of warm ocean waterwarm ocean water that is evaporated and that is evaporated and condensed inside the stormcondensed inside the storm

• Hurricanes MUST form over open warm ocean Hurricanes MUST form over open warm ocean water (water (WARM WATER = WARM WATER = FUEL FOR FUEL FOR HURRICANE)HURRICANE)

• Atlantic Ocean Hurricanes form over the Atlantic Ocean Hurricanes form over the warm water off of the West Coast of warm water off of the West Coast of AfricaAfrica and travel and travel WestWest across the Atlantic via the across the Atlantic via the trade windstrade winds. .

• Since the warm water is where it gets its Since the warm water is where it gets its energy from, hurricanes energy from, hurricanes weaken as they pass weaken as they pass over land or colder waterover land or colder water

• Since hurricanes are extreme Since hurricanes are extreme low pressurelow pressure storms, the winds blow storms, the winds blow in towards the in towards the centercenter of the storm, and it spins of the storm, and it spins counter- counter-clockwiseclockwise (in the Northern Hemisphere) (in the Northern Hemisphere)

• A “tropical storm” is designated a A “tropical storm” is designated a “hurricane” when its winds reach “hurricane” when its winds reach 74 mph74 mph (and vice versa).(and vice versa).

• Hurricanes are classified by the Saffir-Hurricanes are classified by the Saffir-Simpson Scale as Category 1 (Simpson Scale as Category 1 (weakestweakest) – ) – Category 5 (Category 5 (strongeststrongest))

• On average, hurricanes are On average, hurricanes are 400 miles400 miles wide wide• The The eyeeye of the hurricane is the center of the hurricane is the center

where there are no clouds or precipitation where there are no clouds or precipitation and the weather is generally calmand the weather is generally calm

• All hurricanes are named in each ocean in All hurricanes are named in each ocean in alphabetical order, with alternating male alphabetical order, with alternating male and female namesand female names

Hurricanes – Some factsHurricanes – Some facts

• Hurricanes, Typhoons and Cyclones are all Hurricanes, Typhoons and Cyclones are all the SAME THING!!!the SAME THING!!!

• Different Ocean = Different NameDifferent Ocean = Different Name– Atlantic & East Pacific = HurricaneAtlantic & East Pacific = Hurricane– Indian & South Pacific = CycloneIndian & South Pacific = Cyclone– West Pacific = TyphoonWest Pacific = Typhoon

• The three parts of a hurricane that The three parts of a hurricane that cause the most damage are cause the most damage are storm storm surgesurge, , high windshigh winds and and intense intense precipitationprecipitation

• Storm surgeStorm surge is the term used for the is the term used for the water that a hurricane blows onto the water that a hurricane blows onto the shore, causing shore, causing severe floodingsevere flooding and and extreme property damageextreme property damage

• Most fatalities (deaths) are caused by Most fatalities (deaths) are caused by people drowning in the storm surge people drowning in the storm surge (many foolish people do not (many foolish people do not evacuateevacuate areas when told to do so)!!areas when told to do so)!!

• Storm surge is what caused the Storm surge is what caused the flooding in New Orleans and the Gulf flooding in New Orleans and the Gulf Coast during Coast during KatrinaKatrina

Hurricanes – How they Hurricanes – How they cause damage…cause damage…

And now, some very And now, some very cool pictures of cool pictures of

hurricanes…hurricanes…

The “eye” of the hurricane is the center portion where there are no clouds

This is a picture of an eyewall of a hurricane!!! The eyewall surrounds the calm eye and is the most dangerous part of a

hurricane with the highest winds and most intense precipitation.

Hurricane Katrina – August 29th, 2005

Hurricane damage can range Hurricane damage can range from broken windows to from broken windows to complete demolition of buildings. complete demolition of buildings. Until Katrina, Andrew in 1992 Until Katrina, Andrew in 1992 was the costliest hurricane for was the costliest hurricane for the USA with a price tag of over the USA with a price tag of over 20 BILLION dollars!20 BILLION dollars!

Katrina is now reaching a cost of Katrina is now reaching a cost of 200 BILLION DOLLARS!!!!200 BILLION DOLLARS!!!!

Yes, hurricanes are very cool Yes, hurricanes are very cool and interesting…and interesting…

But, they can also be very But, they can also be very deadly to people and costly deadly to people and costly

to the economy. What to the economy. What should people do to prevent should people do to prevent loss of life and damage to loss of life and damage to

structures? structures?

A Public emergency preparedness A Public emergency preparedness plan for hurricanes should haveplan for hurricanes should have

Warning system – TV/Radio/Internet

Evacuation routes and signs so people can get out before the storm surge.

Emergency shelters for people to go to if they can’t evacuate or they are made homeless by the storm

Building/construction codes that minimize damage – ex – no mobile homes/weakly built structures

Emergency equipment/ supplies ready to come in as soon as the storm is over.

A Family/Personal emergency A Family/Personal emergency preparedness plan for preparedness plan for

hurricanes should consist hurricanes should consist of… of… Where to go?

Evacuate the area if you are in the storm surge warning area

What to have? Bottled water/canned food/battery

powered radio/flashlight/cash/ emergency contact numbers/extra clothes

What to do? Board up the windows of your home to

minimize damageStay evacuated until given the OK by the

authorities to return