Atmosphere And Weather

An Overview on Hurricane Categories



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Hurricanes, and their tropical cousins, cyclones, are classified into five categories based on their wind speed, storm surge, central pressure, damage potential. Building codes, local and federal emergency management systems, and even building and discount chains use what is known as the Saffir-Simpson Hurricane scale to set minimum standards for home building, disaster planning, and what types of goods and services need to be on hand in hurricane prone areas. Unfortunately, the scale does not include rain fall, storm speed, or tornado potential, all of which are serious considerations during a hurricane.

CATEGORY 1 – MINIMAL

Hurricanes in this category do little property damage. Wind speeds are 74 – 95 miles per hour, so damage occurs to signage, vegetation, unsecured mobile homes. Storm surge is four to five feet, so damage may occur to piers and there may be some costal road flooding. Central pressure is generally above 980 millibars.

CATEGORY 2 – MODERATE          

These hurricanes, with wind speeds of 96 – 110 miles per hour do considerable damage to vegetation. Trees and poor constructed signs may blow down, windows may suffer damage due to flying debris. Mobile homes will suffer damage as will most roofs and doors. Most well constructed or large buildings will survive and few if any smaller buildings will be totally destroyed. A storm surge of six to eight feet almost guarantees damage to piers, anchored boats, coastal roads, and marinas. Central pressure will drop to 965 – 979 millibars.

CATEGORY 3 – EXTENSIVE

With winds of 111 – 130 miles per hour, trees, signage, small buildings, and mobile homes will all be destroyed. Larger buildings will survive but usually with damage to roofs and doors. Flooding will be considerable with storm surges in the nine to twelve foot range. Evacuation of low lying areas generally occurs at this point. Central pressure hovers around 945 to 964 millibars.

CATEGORY 4 – EXTREME

Wind speeds increase to 131 – 155 miles per hour, flattening smaller buildings and mobile homes. Trees are uprooted and signs are crushed. A storm surge of thirteen to eighteen feet guarantees evacuation, and on flat terrain, the surge may come as far inland as six miles. Central pressure falls to between 920 and 944 millibars

CATEGORY 5 – CATASTROPHIC

As the name suggests, this is a catastrophic event. The wind howls at over 155 miles per hour. Only the strongest, well designed structures will survive albeit with damage to the lower floors due to flooding. A storm surge of eighteen feet frequently causes evacuation of up to ten miles inland. Flooding is extensive. Central pressure falls to 920 millibars, frequently sparking tornadic activity.

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