Hurricanes-Green

Hurricanes Jonny S. & Clara B.-G. Green Class

Introduction What is it: A hurricane is a type of tropical cyclone (a low pressure system) with winds that exceed 64 knots, (74mph, 119km/h) accompanied by thunderstorms and a counterclockwise and inward circulation in the Northern Hemisphere (clockwise in the Southern hemisphere). They are typically about 300 miles in diameter. Before it is classified as a hurricane, it must pass through the categories of Tropical Depression, then Tropical Storm. (1, 2, 7) Where: Hurricanes happen in the tropics because of the warm water. (1) When: From June to November (usually). (2) 

Dangers Dangers of categories 1-5: (4,7) Category 1: Wind speeds of 74-95mph, with a storm surge of 4-5 feet. Most damage is minimal, or can occur on mobile homes, or trees and bushes. Slight coastal flooding can happen.

Category 2: Wind speeds of 96-110mph, the storm surge can range from 6-8 feet. Damage is inflicted on some roofing, with severe plant damage. Unanchored homes can be at risk for much damage. Smaller boats can break their moorings.

Category 3: Wind speeds of 111-130mph, with a 9-12 foot storm surge. Some buildings may begin to be at risk at these wind speeds. Mobile homes are obliterated. Floating debris can damage large structures, while small structures can be damaged beyond repair. Flooding may begin to occur inland.

Category 4: Wind speeds ranging from 131 to 155mph. The storm surge can be anywhere from 13-18 feet. Small residences can experience almost total roof failure. Beaches can erode extensively. Again, inland, terrain may be flooded.

Category 5: Wind speeds excede 155mph. And the water surge is over 18 feet. A surge this high may lead to major inland flooding and damage to the floors of homes close to shore. Roof failure may occur on many industrial buildings. Some total building destruction, and mass evacuation of costal regions are likely.

why do hurricanes happen?
Hurricanes occurs over warm water (+ 26.5 C), low pressure zones because moist air and heat are needed for the formation of the hurricanes. Wind moves from higher pressure to lower pressure, the steeper the pressure gradient the faster windspeed (pressure gradient is the amount of pressure change between a high and low pressure point). That is why wind moves towards the center of a low pressure zone, creating surface convergence, which causes air to rise.

What causes wind to move in a spiral (counterclockwise in the Northern Hemisphere) is the Coriolis effect. Once air rises in a counterclockwise motion, clouds are created since the low pressure air raised expanded and cooled. This forms clouds because when air cools the capacity lowers, increasing the relative humidity. Once the air air reaches it's dew point temperature, the air condensates forming clouds. As a result, the air is very humid since the warm water from the ocean keeps on evaporating, which creates continuous severe weather. The difference between a hurricane and a cyclone, is the air of the hurricanes is much hotter and humid, due to the warm water, and therefore much more unstable.

Historical Examples Deadliest U.S hurricane (5,6) - [|Great Galveston Hurricane] Year: 1900 (5,6) Category: 4 (5,6) Location: Texas Deaths: 8000 Estimated Wind Speed at landfall: 145mph (233 km/h) History: The reason why the Galveston hurricane caused so much harm and destruction is because the habitants weren't prepared for a category 4 hurricane. (5) The Weather Bureau official in charge locally, Isaac M. Cline, drove a horse-drawn cart around low areas warning people to leave. Few people had actually evacuated the city. Before bridges from Galveston Island to the mainland fell, many people along the beach waited until too late to seek shelter in large buildings in a safer area downtown, away from the Gulf. Property damage is impossible to estimate by current standards, but contemporary figures ranged from twenty to thirty million dollars. A high-water mark of 15.7 feet and high winds had destroyed a third of the city, including 2,636 houses and 1,500 acres of shoreline (6)

Safety 1. Be aware: (3) i. Do you live in an evacuation area? ii. Know your home's vulnerability to storm surge and flooding iii. Determine self evacuation routes inland iv. Trim trees and shrubbery v. Pet plan 2. Be prepared (4) i. Buy food that will keep and drinking water ii. Fuel automobiles iii. Check emergency kit: flashlight (batteries), medicine kit, clothing (sturdy shoes), cash, telephones, toys, and important documents **During storm: (3,4)** i. Evacuate if you are told so ii. Have food, money, and batteries with you (4) iii.Store lawn furniture and other loose, light-weight objects, such as garbage cans and garden tools. Sources 1) "Hurricane Basics." //National Hurricane Center//. NOAA. Web. 9 Jan. 2012. . 2) "Hurricanes." University of Illinois, 2010. Web. 10 Jan. 2012. . 3) "Weather Safety: Hurricanes." //Hurricanes//. NOAA. Web. 12 Jan. 2012. . 4) "Hurricane Dangers." //Hurricanes//. CaymanPrepared.ky. Web. 12 Jan. 2012. . 5) "Deadliest US Hurricanes." Wunderground.com. Web. 15 Jan. 2012. . 6) "GALVESTON HURRICANE OF 1900 | The Handbook of Texas Online| Texas State Historical Association (TSHA)." //Texas State Historical Association (TSHA) | A Digital Gateway to Texas History//. Web. 15 Jan. 2012. . 7) Allaby, Michael. "Hurricane Growth." //Hurricanes//. US of America: Facts on File Science Library, 2003. 37, 9, 24. Print.
 * Before storm: **