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Tropical Weather» Tropical Cyclone Scales
Tropical Cyclone Scales
All hurricanes are dangerous, but some are more so than others. The way storm
surge, wind, and other factors combine determines the hurricane's destructive power.
To make comparisons easier, and to make the predicted hazards of approaching
hurricanes clearer to emergency forces, hurricane forecasters use a disaster-potential
scale, which assigns storms to five categories. Category 1 is a minimum hurricane;
category 5 is the worst case scenario. The criteria for each category are shown
below. The winds are used in the determination of category.
| CATEGORY |
PRESSURE (MB) |
CENTRAL WINDS (MPH) |
SURGE DAMAGE (FEET) |
STORM EXAMPLE AND YEAR |
1
MINIMAL |
980+ |
74 - 95 |
4 - 5 |
JERRY 1989 |
2
MODERATE |
965 - 979 |
96 - 110 |
6 - 8 |
KATE 1965 |
3
EXTENSIVE |
945 - 964 |
110 - 130 |
9 - 12 |
ALICIA 1983 |
4
EXTREME |
920 - 944 |
131 - 155 |
13 - 18 |
CARLA 1961 |
5
CATASTROPHIC |
920 |
155+ |
18+ |
CAMILLE 1969
ANDREW 1992 |
Effects
- Category 1 - Minimal damage to building structures. Damage
primarily to unanchored mobile homes, shrubbery, and trees. Also, some
coastal road flooding and minor pier damage.
- Category 2 - Some roofing material, door, and window damage
to buildings, Considerable damage to vegetation, mobile homes, and piers.
Small craft in unprotected anchorages break moorings.
- Category 3 - Structural damage to small residences and utility
buildings with a minor amount of curtainwall failures. Mobile homes are
destroyed. Flooding near the coast destroys smaller structures with larger
structures damaged by floating debris.
- Category 4 - More extensive curtainwall failures with some
complete roof structure failure on small residences. Major erosion of
beach areas. Major damage to lower floors of structures near the shore.
- Category 5 - Complete roof failure on many residences and
industrial buildings. Some complete building failures with small utility
buildings blown over or away. Major damage to lower floors of all structures
located less than 15 feet above sea level.
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