Hurricanes

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Hurricanes

• Geog 225

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What Is A Hurricane?

• A hurricane is one of the most destructive
  natural, regularly occurring forces on Earth.
• A hurricane can produce the heat of a 10 megaton
  nuclear bomb every 20 minutes.

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Hurricane Season

• Starts June 1st
• Tropical depressions, storms, and hurricanes are
  mostly likely to form in August
• Ends November 30th
• 97 of tropical storms occur between these dates

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Tropical Disturbance

• Set of thunderstorms caused by a change in
  absolute vorticity.
• They develop off of the west coast of Africa.
• Easterly waves develop from the interaction of
  the hot air of the Sahara desert and cooler
  coastal air.
• Not many of these form into big storm systems

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Tropical Depression

• Once the disturbance grows into a more complex
  storm, it is labeled a tropical depression.
• Wind speed is around 30-39 miles per hour
• May have one or more closed isobars
• Not named

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Tropical Storms

• When the wind speed is more than 39 miles per
  hour, but less than 74.
• Named when it reaches this stage, alternating
  male and female names off of the name list for
  the hurricane season.

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Hurricanes

• Wind speed greater than 74 miles per hour
• Becomes more complex at this stage and large
• Relatively high pressure gradients
• Release large amounts of energy
• Maintains complex flows of air
• Made up of numerous storms
• Have a calm area in the center, named the eye

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The Eye Of The Hurricane

• Usually warmer than the rest of the storm
• Clear and calm
• The smaller the eye, the stronger the storm is

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Eye Wall

• Strongest part of the hurricane
• Can have enormous amounts of rain
• Can have high wind speeds (possibly 210 mph or
  higher)

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Category One Hurricanes

• Winds of 74-95 miles per hour
• Storm surge 4-5 feet above normal
• Minimal damage
• Could be minor flooding and pier damage
• Recent Category One Allison and Danny

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Category Two Hurricanes

• Winds of 96-110 miles per hour
• Some damage to roofing, doors, and windows
• Storm surge 6-8 feet above normal
• Plenty of damage to mobile homes and piers
• Recent Category Two Bonnie and George

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Category Three Hurricanes

• Winds of 111-130 miles per hour
• Storm surge 9-12 feet above normal
• Some structural damage to small residences and
  utility buildings
• Mobile homes are destroyed
• Coastal flooding is present
• Recent Category Three Roxanne and Fran

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Category Four Hurricanes

• Winds 131-155 miles per hour
• Storm surge 13-18 feet above normal
• Small residences could lose their roofs
• Mobile homes completely destroyed
• Extensive flooding hours before the center of the
  storm hits
• Recent Category Four Luis and Opal

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Category Five Hurricanes

• Wind speed greater than 155 miles per hour
• Storm surge 18 feet above normal
• Many residences are damaged or completely
  destroyed
• Major flooding
• Recent Category Five Mitch and Gilbert