The intensity of a hurricane making landfall, or coming ashore, is measured by categories that indicate wind speeds and potential damage. According to the Saffir-Simpson Hurricane Scale, a Category 1 hurricane has winds of 74-95 miles an hour. A Category 2 storm causes considerable damage with its winds of 96-110 miles an hour. A Category 3 hurricane is measured with sustained winds of 111-129 miles an hour and a Category 4 hurricane tops out between 130 and 156 mph. The rarely seen Category 5 storm has winds of 157 miles an hour or more and causes catastrophic damage.
Even tropical storm-force winds are 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 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 to people's every day lives. And the strongest winds usually occur on the right side of the eye wall 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 wind gusts to nearly 100 mph.
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 rain bands, 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 hurricanes making it to shore produce at least one tornado; Hurricane Buelah (1967) spawned 141 according to one study. In general, tornadoes associated with hurricanes are less intense than those that occur in the Great Plains (see the Fujita Intensity Scale below). Nonetheless, the effects of tornadoes, added to the larger area of hurricane-force winds, can produce substantial damage.
The National Weather Service does not have an accurate way 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. Because of that, being prepared and having a plan is critical.