Five Categories of a Hurricane

Saffir-Simpson Scale Is Used to Estimate Potential Damage to Coasts

Sep 2, 2008

By assigning a category to a hurricane, scientists are able to warn coastal populations as to the probable intensity of the hazard and help prepare residents.

The end of the summer season is always a busy time for meteorologists due to an increase in the frequency of tropical storms and hurricanes. To aid in risk awareness and hazard mitigation, scientists created a scale to characterize the intensity of a hurricane as it relates to wind speed and storm surges. In the scientific community, this scale is known as the Saffir-Simpson scale; but in the media this scale is used to assign a hurricane category.

The Saffir-Simpson Scale

The Saffir-Simpson scale was created in 1969 by civil engineer Herbert Saffir and the then director of the U.S. National Hurricane Center, Robert Simpson. Saffir, inspired by another natural hazard scale – the Richter earthquake magnitude scale – wanted to develop a hurricane intensity scale that could provide an approximation of how much property damage could be expected from any given hurricane. Simpson complemented Saffir’s scale by adding an approximation of storm surge heights accompanying hurricanes and how far inland they could flood.

Hurricane Categories

There are five hurricane categories that are based on the Saffir-Simpson scale. Low intensity hurricanes are assigned a Category 1 hurricane. As the intensity of a hurricane increases, it is assigned a higher category value.

Category 1 hurricanes produce sustained wind speeds of 74-95 miles per hour (mph) and storm surges of 4-5 feet above normal. Damage is limited to temporary structures and there will be some flooding of roads on the coast and possibly some pier damage.

Category 2 hurricanes produce wind speeds of 96-110 mph and storm surges are generally 6-8 feet above normal. Damage to permanent structures includes wind damage to roofing and some window damage. Some trees can be blown down and coastal escape routes should be avoided as they may be dangerously flooded. Small crafts left in the water may break away from their moorings.

Category 3 hurricanes produce wind speeds of 111-130 mph and storm surges that can be 9-12 ft above normal. Structural damage to small buildings beyond broken windows and roofs is possible and temporary structures can be totally destroyed. Large trees may be blown down and foliage that has been blown off trees can become hazardous debris. Terrain that is lower than 5 feet above sea-level can be flooded as far as 8 miles inland and evacuation of low-lying populated areas may be required.

Category 4 hurricanes produce wind speeds of 131-155 mph and storm surges generally 13-18 ft above normal. More extensive damage to structures can occur with some roofs being completely blown off buildings. Trees and street signs are blown down with resultant debris being blown around. Terrain lower than 10 feet above sea level may be flooded, requiring massive evacuation of populated areas as far as 6 miles inland.

Category 5 hurricanes produce wind speeds greater than 155 mph and storm surges generally greater than 18 ft above normal. With these high speed winds, most modern residential structures can be severely damaged and roof failure is common even with industrial buildings. All trees and street signs will be completely blown away and windows and doors will be completely destroyed. Storm surges will cause extensive damage to the lower floors of buildings located less then 15 feet above sea-level and within 500 yards of shoreline. Populated areas on low ground within 5-10 miles of shorelines will need to be evacuated.

Source:

Kantha, L., 2006. Time to Replace the Saffir-Simpson Hurricane Scale?, EOS V. 87 (1).

The copyright of the article Five Categories of a Hurricane in Weather Forecasting is owned by Alexandra Matiella Novak. Permission to republish Five Categories of a Hurricane in print or online must be granted by the author in writing.