HurricanesJennifer, Kevin, Chris, Alisha

What is a Hurricane? • A hurricane is a type of tropical cyclone, which is a

generic term for a low pressure system that generally forms in the tropics. The cyclone is accompanied by thunderstorms and counterclockwise circulation of winds. A tropical cyclone becomes a hurricane once the winds reach 39 mph.

Video • http://

www.youtube.com/watch?v=RzazvxXfhI0&NR=1&feature=endscreen

How Hurricanes Form• Only tropical cyclones that form over the Atlantic

Ocean or eastern Pacific Ocean are called "hurricanes.

• Tropical cyclones are like giant engines that use warm, moist air as fuel. That is why they form only over warm ocean waters near the equator. The warm, moist air over the ocean rises upward from near the surface. Because this air moves up and away from the surface, there is less air left near the surface. Another way to say the same thing is that the warm air rises, causing an area of lower air pressure below.

..Continue How it is Form • Storms that form north of the

equator spin counterclockwise. Storms south of the equator spin clockwise. This difference is because of Earth's rotation on its axis.

• As the storm system rotates faster and faster, an eye forms in the center. It is very calm and clear in the eye, with very low air pressure. Higher pressure air from above flows down into the eye.

Damage• The Saffir-Simpson hurricane scale classifies hurricanes by wind speed. Officially, the Saffir-

Simpson scale is used only to describe hurricanes forming in the Atlantic Ocean and northern Pacific Ocean. Other areas use different scales to label these storms, which are called “cyclones” or “typhoons” depending on the area.

• This scale separates hurricanes into 5 different categories...

• Category 1:• 74-95 mph winds. These storms usually cause no significant structural damage; however they

can topple unanchored materials as well as uproot numerous trees. Even though it is the least intense type of hurricane, the storm can still produce widespread damage and be a life-threatening storm.

• Examples: Danny (1985), Humberto (2007) and Isaac (2012).

• Category 2:• 96-110 mph winds. Storms of Category 2 often damage roofing material and damage poorly

constructed doors and windows. Small craft in unprotected anchorages may break their moorings. Minor power outages are likely and may last days.

• Examples: Erin (1995), Alma (1996) and Ernesto (2012).

Damage• Category 3:• 111-129 mph winds. Tropical cyclones of Category 3 are described as major hurricanes.

These storms can cause some structural damage to small residences and buildings- particularly those of wood frames. Buildings that lack a solid foundation are usually destroyed. A large number of trees are uprooted and/or snapped leaving many areas isolated. Additionally, terrain may be flooded well inland. Near to total power loss is likely for up to several weeks.

• Examples: Roxanne (1995), Fran (1996) and Sandy (2012).

• Category 4:• 130-156 mph winds. Catastrophic damage will occur. Category 4 hurricanes can destroy

homes that are not structurally sounds to withstand these winds. Heavy, irreparable damage and near complete destruction of gas station canopies and other wide span overhang type structures are common. Mobile and manufactured homes are often flattened. Most trees are uprooted or snapped. These storms cause extensive beach erosion while terrain may be flooded far inland. Electrical and water losses are to be expected for possibly many weeks.

• Examples: Galveston Hurricane of 1900, Charley (2004) and Dennis (2005).

Damage• Category 5:• Wind speeds of at least 157 mph. Catastrophic damage will occur. Category

5 is the highest category that a tropical cyclone can obtain in the Saffir-Simpson scale. These storms cause complete roof failure on many residences and industrial buildings and some complete building failures. Collapse of many wide-span roofs and walls (especially with no interior supports) is common. Buildings that are made of solid concrete or steel frame construction are more suited for enduring hurricanes. Any windows without hurricane-resistant safety glass is going to be destroyed. The storms flooding causes major damage to the lower floors of all structures near the shoreline, and many coastal structures can be completely flattened or washed away. Virtually all trees are uprooted and/or snapped and some may be debarked. Total and extremely long-lived extensive power outages and water losses are to be expected, possibly for up to several months.

• Examples: Andrew (1988), Dean (2007) and Felix (2007).

Pictures of Damage

Hurricane Isaac C1 Hurricane Ernesto C2

Hurricane Dennis C4

Hurricane Andrew C5

Cost of a Hurricane• The costliest hurricane ever recorded in the Atlantic was

Hurricane Katrina, which struck the coastline of Louisiana in August of 2005, causing $108 billion in property damage.

• The most recent- Hurricane Sandy which struck the coastlines of Puerto Rico, North Carolina, New Jersey and New York cost $50 billion in property damage- making Sandy the second most costly.

• Other costliest Atlantic hurricanes:

• Hurricane Ike at $37.5 billion (2008)• Hurricane Wilma at $29.2 billion (2005)• Hurricane Andrew at $26.5 billion (1992)

Sizes of Hurricanes• When the winds in the rotating

storm reach 39 mph, the storm is called a "tropical storm." And when the wind speeds reach 74 mph, the storm is officially a "tropical cyclone," or hurricane.

• Tropical cyclones usually weaken when they hit land, because they are no longer being "fed" by the energy from the warm ocean waters. However, they often move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely.

• The size of a hurricane is usually determined by the diameter of its hurricane- and gale-force winds. The average diameter of hurricane-force winds is 100 miles, while the average diameter of tropical storm (gale) force winds is 300 to 400 miles. However, this varies from storm to storm. For example, Hurricane Carla had a diameter of hurricane-force winds of 300 miles, and diameter of tropical storm (gale) force winds of 500 miles. Hurricane Celia, a small but intense storm, had a diameter of hurricane force winds of 80 miles and gale force winds of almost 200 miles. Other large storms include Hurricane Gilbert in 1988 and Hurricane Camillie in 1969

How we can Better Prepare..• Gather information

• Know if you live in an evacuation area• Assess your risks• Know your home’s vulnerability to storm surge flooding and wind• Keep a list of contact info and reference

• Keep a list of contact info and reference• Hospitals, Red Cross, tv/radio, law enforcement etc.

• Put together a supplies kit• Full tank of gas• Flashlight• Batteries• 3 change of clothes for each member of the family• Blankets• pillows

TWO DIFFERENT HURRICANESHurricane Katrina

• Total fatalities- 1833• Highest winds- 174 mph• Category 5 hurricane• Largest and third

strongest hurricane• Caused 150 billion in

damages• 80% of NO was

underwater• Water at places was 12

feet deep

Hurricane SandyTotal fatalities- 285Highest winds- 115 mphCategory 3 hurricane1100 miles wideCaused 75 billion in damagesTwo storms in one

The End