Saturday, October 27, 2012

Tropical Cyclones

Hurricane Isabel (2003)
A tropical cyclone is a storm system centered about an area of low atmospheric pressure.

Low pressure sets an air mass into motion. This motion would be experience by as wind - wind with measurable intensity and direction.
The term cyclone refers to cyclical wind flow. The direction of wind flow in cyclonic systems is:
  • Counter-clockwise in the Northern Hemisphere, and
  • Clockwise in the Southern Hemisphere,
due to a rotational deflection known as the Coriolis force.

The Coriolis force deflects moving objects when they are viewed in a rotating reference frame such as the earth's rotation. Wind undergoes an apparent deflection from its path because of the rotation of the earth.
Hurricane Sandy 10/26/2012
“There is no way that we can predict the weather six months ahead beyond giving the seasonal average”
Stephen Hawking, from Black Holes and Baby Universes
Tropical cyclones originate over tropical oceans in the equatorial regions of the earth. A cyclone derives its energy from condensed water vapor. Condensation occurs as warm, saturated air rises from the ocean surface (evaporation) and cools.
“One of the fellows called me 'Cyclone' but finally shortened it to 'Cy' and its been that ever since.”
"Cy" Young, Major League Baseball pitcher (1867 – 1955).
A tropical cyclone is also referred to as a hurricane, a typhoon, a tropical storm, a cyclonic storm, a tropical depression, or simply a cyclone, depending on the global region and wind-speed intensity.

Name Wind Speed Global Region
Tropical Depression 38 mph or less
Tropical Storm 40 to 72 mph
Hurricane 74 mph or greater Western North Atlantic and Eastern North Pacific
Typhoon 74 mph or greater Western North Pacific