Page 73 - (DK) Ocean - The Definitive Visual Guide

71

STORM SURGE
Hurricane Frances hits Juno Beach, Florida,
in September 2004. Classed as a Category 2
hurricane when it hit land, Frances caused
a storm surge 6 ft (2 m) high, which ripped
across highways and flooded homes and
business premises.

HURRICANE CATEGORIES Coastal Effects
As it moves across the ocean, the low-pressure
A classification system called the Saffir–Simpson Scale divides hurricanes into five
categories. It is used to estimate the damage and flooding to be expected along a eye of a tropical cyclone sucks seawater up into a
coast impacted by the hurricane. Wind speed is the determining factor in the scale. mound, which can be up to 12 ft (3.5 m) above
sea level for a Category 2 hurricane or 25 ft
(7.5 m) for a Category 5. When the cyclone hits
CATEGORY WIND SPEED HEIGHT OF SURGE
Tropical Storm 39–73 mph (63–118 kph) less than 3 ft (1 m)
land, the water in this mound surges over the
Category 1 hurricane 74–95 mph (119–153 kph) 3–5 ft (1–1.5 m)
coast in what is known as a storm surge. The
Category 2 hurricane 96–110 mph (154–177 kph) 6–8 ft (2–2.4 m)
surge may flood homes, wash boats inland, destroy
Category 3 hurricane 111–129 mph (178–208 kph) 9–12 ft (2.7–3.7 m)
roads and bridges, and seriously erode a section of
Category 4 hurricane 130–156 mph (209–251 kph) 13–18 ft (4–5.5 m)
coastline up to 95 miles (150 km) wide. These
Category 5 hurricane over 156 mph (251 kph) over 19 ft (5.8 m) CORAL DAMAGE
effects compound the devastation caused by high This colony of elkhorn coral was
winds, which can topple unstable buildings, smashed by Hurricane Gilbert on
uproot trees, damage coastal mangroves, and bring Mexico’s Caribbean coast in 1988.
DISCOVERY
down power lines. Human deaths are not
STORM CHASERS uncommon, so coastal areas threatened by
a severe cyclone are normally evacuated in
The United States’ National Oceanic advance. Offshore, the water movements
and Atmospheric Administration associated with a storm surge can devastate
(NOAA) monitors Atlantic
hurricanes using specially coral reefs. In the Caribbean, branching
equipped aircraft. They fly corals that live near the
into hurricanes to drop surface, such as elkhorn WATERSPOUT
instrument packages, corals, are particularly Waterspouts are
which radio back data. vulnerable. Healthy tornados (narrow,
reefs can recover from whirling masses of INTRODUCTION
LOCKHEED WP-3D ORION such damage, although air) over the sea.
This turboprop aircraft, equipped with They are quite
a sophisticated array of instruments, it can take 10–50 years commonly spawned
is one of those used in hurricane study. depending on the around the edges of
extent of injury. tropical cyclones.