When forecasters from the National Weather Service track a hurricane, they use models from several different supercomputers located around the world to make their predictions.
Some of those models are more accurate than others. During Hurricane Sandy last October, the model from the European Center for Medium-range Weather Forecasting in the United Kingdom predicted that the large storm would hit the East Coast, while the American supercomputer model showed Sandy drifting out to sea. The American model eventually predicted Sandy's landfall four days before the storm hit.
The storm hit New Jersey and New York, killed 147 people and caused tens of billions of dollars in property damage.
Most meteorologists agree that the two American supercomputers that provide storm models are underpowered. The National Weather Service plans on upgrading those computers in the next two years.