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Extreme precipitation event:
the Weather Public Alert System
of the Chilean Weather Service
Benjamin Caceres and Jorge F. Carrasco,
Dirección Meteorológica de Chile – Dirección General de Aeronáutica Civil
E
xtreme weather events (EWEs) such as hurricanes, floods,
heat waves and droughts have the potential to cause
death and destruction that can reach catastrophic scales.
Weather-related economic losses have significantly increased
during the last 50 years or so, especially since the 1990s. This
corresponds with the increase in extreme weather events, which
is believed to be caused by the increased concentration of green-
house gases. However, city growth, human modification of the
topography and the use of potentially dangerous areas are among
the factors that have contributed to increasing the number of
disasters related to hazards.
D
isaster
R
isk
R
eduction
An EWE, by its nature, is infrequent or rare and, there-
fore, lies outside of what is considered to be the normal
range of weather intensity that characterizes a particu-
lar area. From the climate viewpoint, EWEs are within
the tails of normal distribution, for example, those
events whose intensity occurs only ten per cent or less
of the time. Besides their rare occurrence, EWEs are
part of the natural variability of the Earth’s system. On
the other hand, an EWE is not necessarily extreme in
the meteorological sense, although it may trigger an
extreme scenario (weather-related disaster) for areas
Erosion caused by increased river flow
Image: La Tercera, junio 2002