Hurricanes: Their Nature and Impacts on Society - Climate Science ...

TROPICAL CYCLONES ON PLANET EARTH
(miles)
0 10 20 30 40 50 60 70 80
~ 10'-20 35'- 40'50 eb' 10 ~O 90' 100 II~ 120 'I~
Radius from center ( km)
of hurricane
Figure 3.8 The structure as a function of distance from the storm center as approximated
by averaging 16 profiles for Hurricane Anita on 2 September 1977. The
temperature line illustrates the warm core of the hurricane. The eye wall is the zone
with the greatest sustained wind speeds <strong>and</strong> the strongest averaged upward motion.
Source: Willoughby (1979)
from the relationship illustrated in Figure 3.11. For instance, in two storms
with identical central pressure, a larger storm will tend to have weaker winds
than a small storm because the horizontal difference in pressure (which drives
the winds) in the larger storm is generally spread over a greater distance.
The deepest pressure, <strong>and</strong> hence maximum wind, that is possible in a
hurricane is well correlated with ocean surface temperature (Miller 1958).
Using the analogy of a heat engine, wind circulation would be expected to be
stronger when the heating from the ocean is greater. A hurricane, for example,
would not, in general, be expected where the ocean surface temperature was
less than 79°F (26°C) (K. Emanuel of the Massachusetts Institute of Technology
produces graphs of maximum expected hurricane intensity based on sea
surface temperature, which are available on the www at http://grads.iges.org/
pix/hurrpot.html). One of the lowest pressures ever observed in an Atlantic
hurricane (892 mb) was in the Labor Day, Florida Keys Storm of 1935 in
which 408 deaths occurred. If Hurricane Andrew (1992) had more time to
intensify, then it could have had a significantly lower central pressure at
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