Hurricanes, Typhoons, Cyclones
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1The Intelligent Citizen’s Guide to His World: Hurricanes—Typhoons—Cyclones
Hurricane, typhoon and cyclone are three names for the same sort of event; people in the Atlantic call
their severe ocean storms hurricanes while those in the Pacific refer to typhoons and those in the Indian
ocean speak of cyclones. For simplicity, I will refer here to them all as hurricanes. Under any name,
they can be devastating when they hit land. When they catch ships at sea, they are often fatal. One off
the Virginia coast sunk most of a huge sixteenth-century Spanish treasure fleet that was sailing back to
Europe from the Caribbean. As an English voyager in 1526 described the storm, it was “a most terrible
and vehement storme, which was the taile of the West Indian Huracano… so violent that men could
scarce stand upon the Dekes, neither could any man heare another speak.” Such gales dismasted ships,
tore their rudders from their moorings, ripped the sails apart, smashed lifeboats and cabins and caved
in decks and hulls.
It was sailors’ tales of such experiences that inspired Shakespeare’s play The Tempest. Then ships
were tiny, wooden and awkward, but even when Joseph Conrad picked up in “Typhoon” where Shake-
speare had left off and steamships were made of steel, the power of the storm was nearly indescribable.
His imaginary ship, the Nan-Shan, survived, but the 152 ships hit by Typhoon Mahina in 1899 (that
probably inspired his tale) simply disappeared beneath the waves. So what are these “ship killers?”
Hurricanes are wind-driven clouds of water va-
por that form in areas of intense low pressure over
warm bodies of ocean water. Generally speaking,
the water must be at least 80ºF (27ºC) so the sea
near the equator is their nursery. As described by
weatherstreet.com, “water vapor is the ‘fuel’ for the
hurricanes because it releases the ‘latent heat of
condensation’ to form clouds and rain, warming
the surrounding air…Usually, the heat released in
this way in tropical thunderstorms is carried away
by wind shear, which blows the top off the thun-
derstorms. But when there is little wind shear, this
heat can build up, causing low pressure to form.
The low pressure causes wind to begin to spiral in-
ward toward the center of the low.” And this in
Hurricanes—Typhoons—CyclonesChapter 3
Image credit: scifiles.larc.nasa.gov/
2The Intelligent Citizen’s Guide to His World: Hurricanes—Typhoons—Cyclones
turn evaporates more water vapor which carries
the process onward. The following sketch, from
the Australian Bureau of Meteorology, shows how
hurricanes develop.
Growing stronger as convection adds more
moisture to the cloud, winds swirl around a sort
of virtual pivot, known as the “eye” of the storm.
In the northern hemisphere, the winds rotate in a
counter-clockwise direction and rotate clockwise
in the southern hemisphere. To stay powerful, a
hurricane must constantly pick up water; thus,
out at sea it may last days or even weeks. But,
shortly after the eye hits land, a hurricane begins to lose power although the effects of the forces it has
generated – heavy rain and a surge of sea water -- may continue for some time their destructive activities.
Dynamic in the extreme, a hurricane has a complex structure. The outer edge is the weakest in
power. Winds gain in power and speed toward the eye. While the eye itself is dead calm, the area that
surrounds it, called the “eye wall,” contains the most intense force. There winds often reach as much
as 200 miles (320 kilometers) per hour.
http://www.spacestationinfo.com/students-29-Hurricane.html Image Credit: World Book
This schematic drawing, developed
by NASA from s atellite images shows
the structure.
http://www.nasa.gov/audience/forstudents/k-4/home/F_How_Strong_Is_That_Hurricane.html
3The Intelligent Citizen’s Guide to His World: Hurricanes—Typhoons—Cyclones
NASA photo of Hurricane Catarina on March 27, 2004 just as it made landfall in Brazil. http://earthobservatory.nasa.gov/IOTD/view.php?id=4369
The “eye wall, where the winds are the most intense, of Hurricane Isabel viewed from the International Space Station on September 15, 2003.
http://spaceflight.nasa.gov/gallery/images/station/crew-7/html/iss007e14896.html
4The Intelligent Citizen’s Guide to His World: Hurricanes—Typhoons—Cyclones
Hurricanes can be enormous. Here is Typhoon Muifa which forced the evacuation of more than
360,000 Chinese as it approached Shandong province and did much damage also in Korea. This
NASA image was taken August 8, 2011.
Hurricane Irene roared up the
East Coast of the USA in August
2011 bringing rains of as much as
240 mm (9 inches), dark blue in
this NASA image (acquired Au-
gust 22-28, 2011), flooding cities
and collapsing buildings, washing
away roads and doing about $7
billion in damage.
http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=51663
http://earthobservatory.nasa.gov/IOTD/view.php?id=51935
5The Intelligent Citizen’s Guide to His World: Hurricanes—Typhoons—Cyclones
Hurricane Katrina arrives over New Orleans on March 30, 2009. http://goes.gsfc.nasa.gov/pub/goes/050829.katrina.jpg
Hurricane Katrina was the
most devastating storms ever ex-
perienced by Americans. It began
to form over the Bahamas on Au-
gust 23, 2005 and rapidly picked
up power as it sucked up vast
clouds of moisture from the ocean.
It reached a high of a category 5
storm with winds of nearly 175
miles (280 kilometers) per hour.
Although somewhat less power-
ful when it struck New Orleans
on August 29, it still killed nearly
2,000 people, did nearly $150 bil-
lion in damages, pushed a surge of sea water 6 to 12 miles (10 to 19 kilometers) inland, flooded about
80% of the city, destroying more than 100,000 houses, and by destroying many oil and gas facilities
severely cut energy production.
Flooded neighborhoods in New Orleans. http://www.katrina.noaa.gov/helicopter/images/katrina-new-orleans-flooding3-2005b.jpg
6The Intelligent Citizen’s Guide to His World: Hurricanes—Typhoons—Cyclones
And the winds wreck buildings
and toss heavy objects around like
toys. They also whip up surges of sea
water that can hurl large boats up on
normally dry land.
http://www.photolibrary.fema.gov/photodata/original/24914.jpg
http://www.noaanews.noaa.gov/stories2005/images/ katrina-bayou-la-batre-ala-2005.jpg
7The Intelligent Citizen’s Guide to His World: Hurricanes—Typhoons—Cyclones
While hurricanes have struck populated areas both in the northern and southern hemispheres
for centuries, a relatively new development appears to have changed their power and frequency:
As an aspect of climate change, the oceans are warming. As water warms, it expands. And, as
it warms and expands, more powerful hurricanes can be anticipated. This is Hurricane Eugene on
August 3, 2011 with sustained winds of 220 kilometers (140 miles) per hour.
NASA Earth Observatory from Aqua Satellite. http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=51622