Page 90 - The World About Us

Hurricane Lee
1.1.1
1.1.1
2.2.32.3.5

What are cyclones, hurricanes and typhoons?

Tropical revolving storms are
weather systems of intense low
pressure which originate over warm
tropical seas between five degrees and
thirty degrees of la tude. Tropical
storms can develop into cyclones, also
known as hurricanes and typhoons,
once wind speeds exceed 118km per
hour.
Tropical cyclones are associated
with very high wind speeds and
intense, heavy rainfall. They can bring
immense damage to island na ons and
coastal areas. The ten most damaging
typhoons in recent years have caused
an es mated $6.5 billion of damage to
the Philippines alone.
Fig.239 Three simultaneous hurricanes, Ka a, Irma and Jose, 8th September 2017.
Across the planet around 80 tropical more damaging. into hurricanes. Of these ten hurricanes,
storms occur each year, with about half five reached Category 3, Harvey hit
developing into cyclones, hurricanes During El Niño events (see page 94), Category 4 and Irma and Maria reached
there tends to be fewer storms in the
and typhoons. The most cyclone prone Category 5. Preliminary es mates for
Atlan c and Caribbean, but more in the
ocean is the Pacific with the strongest hurricane damage during the 2017
storms tending to develop in the Eastern and South Pacific. During La season were put at US$186 billion.
western Pacific. Niña, cyclones are suppressed in the
Central and Eastern Pacific basins but minimum sustained wind speed
Figure 241 shows the regions where enhanced in the Atlan c. SSHWS
tropical storms are generated with an miles per hour kilometres/hour
indica on of the average number of Hurricanes winds are measured 5 ≥157 ≥252
cyclones in each area each year. using the Saffir-Simpson Hurricane
Wind Scale. This scale does not take 4 130-156 209-251
While there does not appear to be into account rainfall and storm damage.
a global increase in the total number of 3 111-129 178-208
tropical storms (except in the Atlan c), The 2017 Atlan c Hurricane season
many scien sts agree that the energy was described by some climate 2 96-110 154-177
levels in many is increasing, making scien sts as ‘hyperac ve’ with sixteen 1 74-95 119-153
tropical storms; 10 of which developed
them more intense and poten ally
Fig.240 Saffir-Simpson Hurricane Wind Scale.
Fig.241 The global
distribu on of hurricanes,
cyclones and typhoons.

9
13 26
2 6
Equator 7
9 9

9
Possible path
13 Mean annual frequency

Zone of genesis, sea temperatures above 27 C

8790

The global circulation of the atmosphere controls weather and climate.Extreme weather conditions cause different natural weather hazards.