Tornadoes
A tornado is a column of violently rotating air, spawned by a thunderstorm, which is connected from the thunderstorm
cloud to the ground. It often appears funnel shaped or as a column of debris. Tornadoes are one of nature's most violent storms. They may develop suddenly, and may contain winds that reach over 250 mph. Tornadoes are a threat to human life and responsible for millions of dollars worth of property damage each year in North Carolina.
In 1971, Dr. Theodore Fujita developed a scale to categorize tornadoes based upon their intensity and area. This scale is known as the Fujita Scale, which relates a tornado's damage to the fastest quarter-mile wind speed at the height of a damaged structure to determine intensity. Over the years, problems have arisen with this scale. For starters, the scale is solely based upon the damage caused by a tornado, which makes it difficult to determine intensity if the tornado moves over an area with no structures. In addition, the scale does not take into account differences between structures based upon how they are constructed. To account for some of these problems, a modified version of this scale known as the Enhanced Fujita Scale was created and put into operation in 2007.
Fujita Scale vs. Enhanced Fujita Scale
| Fujita Scale | Enhanced Fujita Scale | ||||
| F-Scale | Fastest 1/4 Mile Wind Speed | 3-Second Wind Gusts | Type of Damage Done | EF-Scale | 3-Second Wind Gusts |
| F0 (Gale) | 40 - 72 mph | 45 - 78 mph | Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards | EF-0 | 65 - 85 mph |
| F1 (Weak) | 73 - 112 mph | 79 - 117 mph | Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off roads | EF-1 | 86 - 110 mph |
| F2 (Strong) | 113 - 157 mph | 118 - 161 mph | Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated | EF-2 | 111 - 135 mph |
| F3 (Severe) | 158 - 207 mph | 162 - 209 mph | Roof and some walls torn off well constructed houses; trains overturned; most trees in forests uprooted | EF-3 | 136 - 165 mph |
| F4 (Devastating) | 208 - 260 mph | 210 - 261 mph | Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated | EF-4 | 166 - 200 mph |
| F5 (Incredible) | 261 - 318 mph | 262 - 317 mph | Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 meters; trees debarked; steel reinforced concrete structures badly damaged | EF-5 | > 200 mph |
Enhanced Fujita Scale Damage Indicators
| Number | Damage Indicator | Number | Damage Indicator |
| 1 | Small barns, farm outbuildings | 15 | 1-story elementary school |
| 2 | One- or two-family residences | 16 | Junior or senior high school |
| 3 | Single-wide mobile home | 17 | Low-rise building (1-4 stories) |
| 4 | Double-wide mobile home | 18 | Med-rise building (5-20 stories) |
| 5 | Apartment, condo, townhouse (3 stories or less) | 19 | High-rise building (> 20 stories) |
| 6 | Motel | 20 | Institutional building (i.e. hospital, government, university) |
| 7 | Masonry apartment or motel | 21 | Metal building system |
| 8 | Small retail building (i.e. fast food) | 22 | Service station canopy |
| 9 | Small professional building (i.e. doctor office, branch bank) | 23 | Warehouse (tilt-up walls or heavy timber) |
| 10 | Strip mall | 24 | Transmission line tower |
| 11 | Large shopping mall | 25 | Free-standing tower |
| 12 | Large, isolated retail building | 26 | Free-standing pole (i.e. light, flag, luminary) |
| 13 | Automobile showroom | 27 | Tree (hardwood) |
| 14 | Automotive service building | 28 | Tree (softwood) |
For more information regarding the enhanced scale, click here.
An analysis of the climatology of tornadoes in North Carolina for a period of fifty years (1950-1999) is performed using tornado data obtained from the National Climatic Data Center (NCDC) and the National Severe Storms Laboratory (NSSL). The data is examined spatially using a Geographic Information System (GIS) to illustrate tornado patterns across the state. The data is also examined to find evidence of significant trends in tornado occurrences on a geographic scale, time scale, and with relation to population. Analysis suggests that there is an increasing trend in tornado occurrences, tornado days, tornado deaths, and tornado injuries. Analysis also suggests that more tornadoes occur in the southeast and southcentral regions of North Carolina.
Below are a series of charts and maps that summarize the climatology of tornadoes in North Carolina:
- Tornado occurrences, tornado days, tornado deaths, and tornado injuries are increasing
- Most tornado occurrences are of F0 and F1 intensity, however, most tornado injuries and deaths are results of more significant tornadoes
- Most reported tornado occurrences are in southeastern and southcentral North Carolina
- The majority of the intense tornadoes occur in central North Carolina
- The majority of tornado fatalities are the result of a single storm
