Cyclone, Tornado, Hurricane

[MartyJazz]

So I'm reading an article today about a severe cyclone (is there any other kind?) approaching northeastern Australia (see here) and I'm wondering what are the differences among all these meteorological events especially as the Webster's New World Dictionary below cites Australia as a spot for tornado, as opposed to cyclone, activity. You'll notice that each of the definitions seem to cite the others as synonyms. Any practicing or amateur meteorologists out there who can enlighten me?

According to Webster's:

cyclone:

1) loosely, a windstorm with a violent, whirling movement; tornado

or hurricane; 2) Meteorol. a system of rotating winds over a vast

area, spinning inward to a low pressure center (counterclockwise

in the N Hemisphere) and generally causing stormy weather: commonly

called a low, since it coexists with low barometric pressure

tornado:

1) a violently whirling column of air, with wind speeds of c. 160

to 480 km/hr. (c. 100 to 300 mi./hr.), extending downward from a

cumulonimbus cloud, esp. in Australia and the central U.S.: almost

always seen as a rapidly rotating, slender, funnel-shaped cloud

that usually destroys everything along its narrow path

2) in W Africa and the adjacent Atlantic, a severe thundersquall

3) any whirlwind or hurricane

hurricane:

1) a violent tropical cyclone with winds moving at 73 or more miles

per hour, often accompanied by torrential rains, and originating

usually in the West Indian region

[couw]

AFAIK cyclone is a general term for rotating volume of air around a low pressure centre. As such it can cause hurricane winds or storm winds. The use of cyclone for tornado is limited to American english I think. Tornadoes are local, whereas cyclones involve vast masses of air.

[Jazzmoose]

I thought it was cyclone was over water and tornado was over land. But then I thought Charlie Parker played really weird music at one point...

[Big Wheel]

I thought it was cyclone was over water and tornado was over land.  But then I thought Charlie Parker played really weird music at one point...

Not exactly. You can have a tornado over water too (often called a waterspout, and commonly seen in South Florida waters).

I'm pretty sure that the thing in the story Marty linked to is a hurricane. The general rule is that hurricanes are named differently depending on which ocean they're in.

Atlantic-->hurricane

Pacific-->typhoon

Indian-->cyclone

(But they all can just be called tropical cyclones if you want. I think it may be a British/Australian convention to name all hurricane-type storms "cyclones," as this storm is in the southern Pacific, not the Indian. Maybe only storms that threaten east Asia are called "typhoons.")

In general, you would never read a news story about a tornado "approaching" anything. Tornadoes form very quickly and unpredictably and dissipate rapidly. (To add to the confusion, though, a hurricane-type storm will often spawn tornadoes in the areas of it where the winds are highest. Hurricane Andrew did so much damage partly because of these.)

Couw is right that some Americans call tornadoes cyclones too. The thing that took Dorothy to Munchkinland was a Kansas tornado, but Frank Baum had the characters refer to it as "a cyclone."

Edited March 8, 2005 by Big Wheel

[Jazzmoose]

Yeah, that sounds more like it, Big Wheel...now that I'm waking up a little!

[Big Wheel]

It's actually even trickier than I thought. A good primer can be found at this link.

Once the tropical cyclone reaches winds of at least 17 m/s (34 kt, 39 mph) they are typically called a "tropical storm" and assigned a name. If winds reach 33 m/s (64 kt, 74 mph)), then they are called:

"hurricane" (the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean east of 160E)

"typhoon" (the Northwest Pacific Ocean west of the dateline)

"severe tropical cyclone" (the Southwest Pacific Ocean west of 160E or Southeast Indian Ocean east of 90E)

"severe cyclonic storm" (the North Indian Ocean)

"tropical cyclone" (the Southwest Indian Ocean)

Edited March 8, 2005 by Big Wheel

[MartyJazz]

You guys have been great. And a special note of thanks to Big Wheel who introduced yet another term that requires more clarification in this mix, "typhoon". B-)

[BruceH]

hurricane: wide

tornado: narrow

Cyclone? Don't get me started...