Hurricanes are storms which
strengthen over days or even weeks. A
hurricane starts as a tropical cyclone (a low pressure system with a defined
wind circulation that develops over the tropics) and becomes a hurricane when
wind speeds reach over 74mph. They occur
5-15o latitude to the north and south of the equator and move from
there to higher latitudes. The term
hurricane is used only for storms that form over the Atlantic or Eastern
Pacific Oceans.
Hurricane formation is
complex. The water on the surface of the
ocean must be warm enough to evaporate putting heat and moisture into the air
and forming towering clouds with heavy rainfall. A low pressure area develops near the surface
of the ocean. The warm surrounding air
is sucked into the low pressure zone and this air then also rises forcing a
continuous upward flow of warm and wet air with more cloud formation and heavy rain. The wind surrounding this low pressure moves
anticlockwise (in the northern hemisphere) at very high speeds increasing the
strength of the storm. Satellite images
show hurricanes as huge circular bodies of cloud which may be 300 miles
wide. In the centre, the eye, there may not
be any clouds because the eye is the only part of the storm where cold air is
descending. Hurricanes hitting shore can
cause considerable damage, flooding and loss of life.
All hurricanes are given
names. For hundreds of years hurricanes
in the West Indies were named after the Saint’s day on which the storm
occurred. This idea was revived in the
1940s by the American Weather Bureau when short-wave radio came into general
use as a quick way of identifying individual storms. Hurricanes were traditionally given female
names by male meteorologists, however, as the number of female meteorologists
increased there was a call for male names to be used for hurricanes as well,
which has been the case since 1978 [1]. Examples of hurricane names include Andrew,
Carol and Dennis.
On
12th October 2014, Hurricane Gonzalo formed in the east of the
Caribbean Sea. It moved north-westward
and gradually grew stronger until it was classified as a Category 4 major
hurricane, the first in the Atlantic Ocean since Ophelia in 2011. Its peak intensity was recorded on 16th
October with winds reaching top speeds of 145 mph. Gonzalo turned north-eastward and hit Bermuda
on 18th October as a Category 2 hurricane [2] (wind
speeds between 196-110mph) and it is estimated to have caused between $200 and $400
million of damage to the island alone [3]. The hurricane, which was beginning to weaken,
headed for Britain on 20th October and reached the UK on Tuesday 21st
October [4]. Winds of 68mph
were recorded in Wales and the Isle of Wight.
The tail end of Gonzalo resulted in the death of three people in England
and five others, including two children, were injured [5]. All injuries and fatalities were the result
of falling objects, such as trees and concrete blocks. 
An
Epsom College Gold Duke of Edinburgh Expedition to the Peak District was directly
affected by Hurricane Gonzalo. The
participants were battered by high speed winds, resulting in the fear that tents
would be blown away. For some this
became a reality when tent pegs were ripped from the ground at 2.30 am
requiring urgent retrieval. The
following day, wind speeds of 70mph on the high peaks were too dangerous for
the participants to walk and climb through with safety whilst carrying large
packs. Walking routes were therefore changed
but the group still endured strong winds, heavy rain and even hailstones, which
is itself an unusual feature of hurricane weather.
Whilst the Epsom College team
braved the weather, Kinder Downfall, a waterfall in the Peak District which normally
has a 30m drop was having its water blown back upstream by the force of the
Gonzalo winds [6] showing the frightening strength of such a
hurricane even though by the time this hit Britain it was classed as an ex-hurricane! Happily, when the winds subsided, Kinder
Downfall returned to normal and the Epsom College students returned home after
their hurricane experience.
Charlotte
Marquand
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