What is a Hurricane?

A hurricane is a type of tropical cyclone (a generic term for a low pressure system that generally forms in the tropics.) The cyclone is accompanied by thunderstorms and, in the Northern Hemisphere, a counterclockwise circulation of winds near the earth's surface. Tropical cyclones are classified as follows:

• Tropical Depression: An organized system of clouds and thunderstorms with a defined surface circulation and maximum sustained winds* of 38 mph (33 kt**) or less.
• Tropical Storm: An organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds* of 39-73 mph (34-63 kt**).
• Hurricane: An intense tropical weather system of strong thunderstorms with a well-defined surface circulation and maximum sustained winds* of 74 mph (64 kt**) or higher.

Hurricane winds blow in a large spiral around a relative calm center known as the "eye". The eye is generally 20 to 30 miles wide, and the storm may extend outward 400 miles. As a hurricane approaches, the skies will begin to darken and winds will grow in strength. As a hurricane nears land, it can bring heavy rains, high winds, and storm surges. A single hurricane can last for more than 2 weeks over open waters and can run a path across the entire length of the eastern seaboard. August and September are peak months during the hurricane season, that lasts from June 1 through November 30. The hurricane history of coastal Virginia details the effects past hurricanes.

The 74 to 160 mile per hour winds of a hurricane can extend inland for hundreds of miles. Hurricanes can spawn tornadoes , which add to the destructiveness of the storm. Floods and flash floods generated by heavy rains also cause damage and loss of life. Following a hurricane, inland streams and rivers can flood and trigger landslides. Even more dangerous than the high winds of a hurricane is the storm surge -- a dome of ocean water that can be 20 feet at its peak and 50 to 100 miles wide. The surge can devastate coastal communities as it sweeps ashore. Nine out of 10 hurricane fatalities are attributable to the storm surge.

Hurricanes are categorized according to the strength of their winds using the Saffir/Simpson Hurricane Scale. A Category 1 storm has the lowest wind speeds, while a Category 5 hurricane has the strongest. These are relative terms, because lower category storms can sometimes inflict greater damage than higher category storms, depending on where they strike and the particular hazards they bring. In fact, tropical storms can also produce significant damage and loss of life, mainly due to flooding.

The Saffir/Simpson Hurricane Scale can be used to give an estimate of the potential property damage and flooding expected along the coast with a hurricane. The Saffir/Simpson Scale is based upon wind speed, and is shown below:

• Category: One
  • Definition: Winds 74-95 mph
  • Effects: No real damage to building structures. Damage primarily to un-anchored mobile homes, shrubbery, and trees. Also, some coastal road flooding and minor pier damage.
• Category: Two
  • Definition: Winds 96-110 mph
  • Effects: Some roofing material, door, and window damage to buildings. Considerable damage to vegetation, mobile homes, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of center. Small craft in unprotected anchorages break moorings.
• Category: Three
  • Definition: Winds 111-130 mph
  • Effects: Some structural damage to small residences and utility buildings with a minor amount of curtain wall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain continuously lower than 5 feet ASL may be flooded inland 8 miles or more.
• Category: Four
  • Definition: Winds 131-155 mph
  • Effects: More extensive curtain wall failures with some complete roof structure failure on small residences. Major erosion of beach. Major damage to lower floors of structures near the shore. Terrain continuously lower than 10 feet ASL may be flooded requiring massive evacuation of residential areas inland as far as 6 miles.
• Category: Five
  • Definition: Winds greater than 155 mph
  • Effects: Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Major damage to lower floors of all structures located less than 15 feet ASL and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5 to 10 miles of the shoreline may be required.

Note: A "major" hurricane is classified as Category 3 or greater.

As the hurricane season approaches, Hampton Emergency Management and the National Weather Service wants you to be prepared for hurricanes, and their associated effects. Take some time to develop your hurricane plan with your family, friends and co-workers. Planning ahead will lower the chance of injury or even death in the event a hurricane strikes the area.

Unlike other types of severe weather, hurricanes are easily detected and tracked, which means you have time to react to it's approach. Unfortunately, planning for a hurricane is not as easy as going to the local store to pick up some small items. Hurricane planning is a deliberate process that should be accomplished prior to and throughout the hurricane season. Do not wait until the last moment to make your decisions. Hurricanes should not be ignored, as their devastation can have effects over large areas, and it is important to understand the threats and hazards associated with hurricanes.

• Listen to the radio, local television, weather channel or a National Oceanic and Atmospheric Administration (NOAA) radio for information.
• Don't wait until a hurricane watch is issued to begin planning how you will respond. Take responsibility for your safety and plan now.
• Have a plan. have a family planning meeting and discuss how you will prepare and respond to an approaching hurricane. Know what actions you will take to prepare for the hurricane, to include evacuation if necessary. Every family member should be assigned specific tasks to accomplish.
• Mobile homes are particularly vulnerable to damage from high winds. Residents, even those who live in mobile homes with tie-downs, should seek safe shelter when a hurricane threatens. Do not remain in your mobile home, evacuate the area or seek shelter.
• If you plan to evacuate the area, do not wait until the last moment to do so. An early start will allow you to place the storm will behind you. Road network congestion increases as the hurricane approaches, when others who waited too long try to leave the area.
• Ensure your personal disaster kit is prepared, and take it with you if you evacuate the area or if you seek shelter away from your home. This will ensure that you have the basic food, water, clothing and other necessities with you for at least three days.

The National Weather Service uses specific hurricane terms to ensure that people know what to expect in the coming hours.

A Tropical Storm Watch means that conditions with sustained winds from 39-74 MPH are possible in your area within the next 36 hours.

A Tropical Storm Warning means that tropical storm conditions (39-74 MPH sustained winds) are expected in your area within the next 24 hours.

A Hurricane Watch means that hurricane conditions (sustained winds greater than 74 MPH) are possible in your area within 36 hours.

A Hurricane Warning means that hurricane conditions are expected in your area in 24 hours or less.