Hurricane Force Winds
The intensity of a landfalling hurricane is expressed in terms of categories
that relate wind speeds and potential damage. According to the
Saffir-Simpson
Hurricane Scale, a Category 1 hurricane has lighter winds compared to storms in
higher categories. A
Category 4 hurricane would have winds
between 131 and 155 mph and, on the average, would usually be expected to
cause
100 times the damage of the Category 1 storm. Depending on
circumstances, less intense storms may still be strong enough to produce
damage, particularly in areas that have not prepared in advance.
Tropical storm-force winds are strong enough to be 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-force 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.
High-rise buildings are also vulnerable to hurricane-force winds, particularly
at the higher levels since wind speed tends to increase with height. Recent
research suggests you should stay below the tenth floor, but still above any
floors at risk for flooding. It is not uncommon for high-rise buildings to
suffer a great deal of damage due to windows being blown out. Consequently, the
areas around these buildings can be very dangerous.
The strongest winds usually occur in the right side of the eyewall 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 gusts to nearly 100 mph.
The
Inland High Wind Model can be used by emergency managers
to estimate how far inland strong winds extend. The
inland wind estimates can
only be made shortly before landfall when the windfield forecast errors are
relatively small. This information is most useful in the decision-making
process to decide which people might be most vulnerable to high winds at inland
locations.