Charleston Hurricane Preparedness and Response

Hurricane Hazards

High Winds and Tornadoes

The intensity of a landfalling hurricane is expressed in terms of categories that relate wind speeds and potential damage. According to the Saffir-Simpson Hurricane Scale, a Category 1 hurricane has lighter winds compared to storms in higher categories. A Category 4 hurricane would have winds between 131 and 155 mph and, on the average, would usually be expected to cause 100 times the damage of the Category 1 storm. Depending on circumstances, less intense storms may still be strong enough to produce damage, particularly in areas that have not prepared in advance.

Tropical storm-force winds are strong enough to be dangerous to those caught in them. For this reason, emergency managers plan on having their evacuations complete and their personnel sheltered before the onset of tropical storm-force winds, not hurricane-force winds.

Hurricane-force winds can easily destroy poorly constructed buildings and mobile homes. Debris such as signs, roofing material, and small items left outside become flying missiles in hurricanes. Extensive damage to trees, towers, water and underground utility lines (from uprooted trees), and fallen poles cause considerable disruption.

High-rise buildings are also vulnerable to hurricane-force winds, particularly at the higher levels since wind speed tends to increase with height. Recent research suggests you should stay below the tenth floor, but still above any floors at risk for flooding. It is not uncommon for high-rise buildings to suffer a great deal of damage due to windows being blown out. Consequently, the areas around these buildings can be very dangerous.

The strongest winds usually occur in the right side of the eyewall of the hurricane. Wind speed usually decreases significantly within 12 hours after landfall. Nonetheless, winds can stay above hurricane strength well inland. Hurricane Hugo (1989), for example, battered Charlotte, North Carolina (which is 175 miles inland) with gusts to nearly 100 mph.

The Inland High Wind Model can be used by emergency managers to estimate how far inland strong winds extend. The inland wind estimates can only be made shortly before landfall when the windfield forecast errors are relatively small. This information is most useful in the decision-making process to decide which people might be most vulnerable to high winds at inland locations.

Questions To Ask Your Community Leaders

Does your community building code set standards that will help buildings withstand winds in a major hurricane?

Do your shelter facilities include long-span roofs or unreinforced masonry walls (such as gymnasiums) that are vulnerable in high winds?

Against the wind (pdf - 0.2 MB)
Hurricane intensification (mp3 - 0.2 MB)

High wind safety actions before hurricane season

• Find out if your home meets current building code requirements for high-winds. Experts agree that structures built to meet or exceed current building code high-wind provisions have a much better chance of surviving violent windstorms.
• Protect all windows by installing commercial shutters or preparing 5/8 inch plywood panels.
• Garage doors are frequently the first feature in a home to fail. Reinforce all garage doors so that they are able to withstand high winds.
• If you do not live in an evacuation zone or a mobile home, designate an interior room with no windows or external doors as a "Safe Room".
  • Trim dead wood and weak / overhanging branches from all trees.
  • Certain trees and bushes are vulnerable to high winds and any dead tree near a home is a hazard.
  • Consider landscaping materials other than gravel/rock.

High wind safety actions as a hurricane approaches

• Most mobile / manufactured homes are not built to withstand hurricane force winds. Residents of homes not meeting that level of safety should relocate to a nearby safer structure once local officials issue a hurricane evacuation order for their community.
• Once a hurricane warning is issued, install your window shutters or plywood panels.
• When a hurricane warning is issued for your community, secure or bring inside all lawn furniture and other outside objects that could become a projectile in high winds.
• Listen carefully for safety instructions from local officials, and go to your designated "Safe Room" when directed to do so.
• Monitor NOAA Weather Radio.
• Do not leave your "Safe Room" until directed to do so by local officials, even if it appears that the winds calmed. Remember that there is little to no wind in the eye of a hurricane.

High winds during Hugo

The Naval Air Station at Roosevelt Roads, PR reported sustained winds of 104 mph with gusts to 120 mph, which were the highest winds reported from the Caribbean. A ship moored in the Sampit River in South Carolina measured sustained winds of 120 mph. High winds associated with Hugo extended far inland, with Shaw Air Force Base, South Carolina reporting 67 mph sustained winds with gusts to 110 mph and Charlotte, North Carolina reporting 69 mph sustained winds and gusts to 99 mph.

This information courtesy of the NHC.