Tornadoes

One of the most important things you can do to prevent being injured in a tornado is to be aware of the onset of severe weather. If a tornado "watch" is issued for your area, it means that a tornado is "possible." If a tornado "warning" is issued, it means that a tornado has actually been spotted, or is strongly indicated on radar, and it is time to go to a safe shelter immediately. Be sure to listen to local radio and TV stations for updated storm information.

A tornado is a violent storm with whirling winds of up to 300 miles per hour (mph). It appears as a funnel shaped cloud, from gray to black in color, which extends to the ground from the base of a thunderstorm. A tornado spins like a top and may sound like the roaring of an airplane or a locomotive. Tornadoes move at an average speed of 30 mph and generally move from the southwest to the northeast. Their direction can be erratic and change suddenly.

Most tornadoes are likely to occur during the mid-afternoon and evening hours during the months of April, May, and June. However, they have been sighted and caused damage during other months. Fortunately, we in Southeast South Carolina are not subject to many of the larger type tornadoes that are seen in the Midwest. Most of our tornadoes are small and short-lived. However, they still can cause damage, injuries, and fatalities.

You should be familiar with the following terms:
  • Tornado watch: Conditions are favorable for the formation of tornadoes. Be aware of changing weather conditions.
  • Tornado warning: A tornado has been sighted in your area, or is strongly indicated on radar. Take shelter immediately.
  • Tornado: A violent, whirling, funnel-shaped cloud that touches the ground.
  • Funnel Cloud: A violent, whirling, funnel-shaped cloud that does not touch the ground. Many people mistakenly call these tornadoes.
  • Waterspout: A tornado over water.
  • Hurricane damage: Hurricanes can also produce tornadoes that add to the storm's destructive power. Tornadoes are most likely to occur in the right-front quadrant of the hurricane.  However, they are also often found elsewhere embedded in the rainbands, well away from the center of the hurricane.

Some hurricanes seem to produce no tornadoes, while others develop multiple ones. Studies have shown that more than half of the landfalling hurricanes produce at least one tornado; Hurricane Beulah (1967) spawned 141 according to one study. In general, tornadoes associated with hurricanes are less intense than those that occur in the Great Plains. Nonetheless, the effects of tornadoes, added to the larger area of hurricane-force winds, can produce substantial damage.

We have no way at present to predict exactly which storms will spawn tornadoes or where they will touch down. The new Doppler radar systems have greatly improved the forecaster's warning capability, but the technology usually provides lead times from only a few minutes up to about 30 minutes. Consequently, preparedness is critical.

Tornados Associated with Hurricanes
  • When associated with hurricanes, tornadoes are not usually accompanied by hail or a lot of lightning.
  • Tornado production can occur for days after a hurricane landfall when the tropical cyclone remnants maintain an identifiable low pressure circulation.
  • They can also develop at any time of the day or night during landfall. However, by 12 hours after landfall, tornadoes tend to occur mainly during daytime hours.

    Fujita scale

The Fujita scale (F-scale) uses actual damage to determine a tornado’s wind speed.

  • F0 Gale Tornado
          40-72 mph
          Some damage to chimneys. Tree branches broken off. Shallow rooted trees uprooted.
  • F1 Moderate Tornado
          73-112 mph
          Peels surface off roofs. Mobile homes overturned. Moving autos pushed off roads.
  • F2 Significant Tornado
          113-157 mph
          Considerable damage. Roofs torn off frame houses. Large trees snapped or uprooted. Light-object missiles generated.
  • F3 Severe Tornado
          158-206 mph
          Severe damage. Roofs and some walls torn off well-constructed homes. Trains overturned. Most trees in forests uprooted. Heavy cars lifted off ground.
  • F4 Devastating Tornado
          207-260 mph
          Well-constructed houses leveled. Structures with weak foundations blown off some distance. Cars thrown and large missiles generated.
  • F5 Incredible Tornado
          261-318 mph
          Strong frame houses lifted off foundations and disintegrated. Automobile-sized missiles fly through the air in excess of 100 mph. Trees debarked.

    Look out for:

        * Dark, often greenish sky
        * Wall cloud
        * Large hail
        * Loud roar; similar to a freight train

    Caution:

    Some tornadoes appear as a visible funnel extending only partially to the ground. Look for signs of debris below the visible funnel.
        

    Some tornadoes are clearly visible while others are obscured by rain or nearby low-hanging clouds.
Tornado Preparedness Tips:

For Tornado Watches:

1. Stay tuned to local radio or your NOAA weather radio.

2. Secure any loose objects outdoors, or move them inside.

3. Survey local structures for the most suitable shelter.

4. Keep watching the sky. If you see any funnel shaped clouds, report them immediately to the nearest law enforcement agency or emergency management.

For Tornado Warnings:

Take shelter immediately!

1. In a Motor Vehicle: This is the least desirable place to be. Do not try to outrun the funnel cloud or tornado. Do not get under or next to your vehicle. Try to find indoor shelter immediately. If all else fails, try to find a ditch or depression to get in.

2. At School: Follow the school disaster plan. Stay away from gyms and auditoriums. Go into center hallways and stay away from windows.

3. Open Country: Move away from the tornado at a right angle. Seek shelter in a ravine, ditch, or culvert. A low spot in the ground will give you some protection.

4. At Home: Stay away from windows. Move into an area with no windows such as a bathroom or a closet. The bathroom is the safest due to the fact that the plumbing gives extra support to the walls. Also, your bathtub may be able to provide you with some protection.

5. In a Mobile Home: This is another one of the least desirable places to be. Seek other shelter immediately. Go to another shelter on foot, if possible. Do not get under your mobile home. Lie in a ditch or other ground depression if all else fails.

Compared with other States, South Carolina ranks number 24 for frequency of Tornadoes, 24 for number of deaths, 23 for injuries and 24 for cost of damages. When we compare these statistics to other states by the frequency per square mile, South Carolina ranks number 18 for the frequency of tornadoes, number 21 for fatalities, number 18 for injuries per area and number 18 for costs per area. Based on data from 1950 - 1995.

Tornado Myths:

MYTH: Areas near rivers, lakes, and mountains are safe from tornadoes.
FACT: No place is safe from tornadoes. In the late 1980's, a tornado swept through Yellowstone National Park leaving a path of destruction up and down a 10,000 ft. mountain.

MYTH: The low pressure with a tornado causes buildings to "explode" as the tornado passes overhead.
FACT: Violent winds and debris slamming into buildings cause most structural damage.

MYTH: Windows should be opened before a tornado approaches to equalize pressure and minimize damage.
FACT: Opening windows allows damaging winds to enter the structure. Leave the windows alone; instead, immediately go to a safe place.

Tornadoes Occur Anywhere

Carolinas Outbreak:

March 28, 1984, afternoon-evening
22 tornadoes
57 deaths
1,248 injuries
damage $200 million
37% of fatalities in mobile homes