Environmental Engineering Reference
In-Depth Information
over West Africa and progressed across the Atlantic, gradually developing the structure
of a tropical disturbance. As it approached the northern coast of South America it began
to develop further and on 22 October it was technically classified as a tropical depression
(Figure 1). Within four days it intensified to become a Category 5 hurricane with a
central pressure of 905 hPa and sustained winds of 155 knots. Unfortunately its
movement slowed and it remained close to the north coast of Honduras for three days
before moving inland and across the Guatemalan mountains. By 2 November it had
declined to a weak depression through loss of its main energy source of the warm ocean.
Crossing Mexico, it reached the Gulf coast and began to intensify again over the warm
waters of the Gulf of Mexico. Moving rapidly north-eastwards, it crossed Florida, then
moved out into the north Atlantic, eventually becoming a mid-latitude depression.
Figure 1
Track of hurricane Mitch across central
America between 22 October and 5 November
1998.
In these different phases of Mitch's existence the full fury of a tropical storm was
demonstrated. Whilst off the north coast of Honduras the strong winds generated huge
storm waves with surges estimated to be up to 13ยท5 m. Once over land, the effects of the
hurricane and the mountains produced enormous amounts of rainfall. The spirals of cloud
around the eye of the storm swirled in from both the Caribbean and the Pacific, focusing
moisture into the critical region. The slow movement of the storm meant that these
conditions prevailed for many hours and rain fell at the rate of 300-600 mm per day.
Estimates of rainfall totals in the mountains approaching 2000 mm have been reported for
the entire storm and even on coastal areas well over 200 mm fell in some areas. With
such volumes of rain it is not surprising that the floods were devastating, and the resulting
mudslides added to the problems of the infrastructure. Whole villages and their
inhabitants were swept away in the torrents of water and mud that flowed down the steep
