Tropical cyclones are large whirling storms that obtain their energy from warm ocean waters. They stand out on satellite photographs due to their circular cloud patterns and, in the stronger storms, a nearly clear eye at the center. The clarity and size of the eye on satellite images helps meteorologists estimate a cyclone's strength.

You can use the following fader to shift from a visible image of Hurricane Iris to an enhanced infrared image at 1742 UTC on October 8th, 2001. The eye of Hurricane Iris shows up particularly well in these images since the eye is a region of subsidence (downward motion) and therefore lack of cloud cover. For the enhanced infrared image, the eye is evident because the satellite is seeing all the way to the surface of the ocean, therefore warmer temperatures are seen compared to the surrounding colder cloud top temperatures of the eye wall region. In addition, the visible image shows more texture in the eye wall region, signifying cumulonimbus clouds.

The lone surface observation plotted on the images signifies counterclockwise (cyclonic) rotation of the tropical cyclone at the surface. It would have been nice to have more surface wind observations around the tropical cyclone area, but as is always the case, surface observations are hard to come by over the ocean, which is why satellite derived winds are so important for forecasting hurricane tracks.