Hurricanes, Typhoons, Cyclones

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/


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


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


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


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


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


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

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Hurricanes, Typhoons, Cyclones