More on Hurricane Prediction
Hurricane Tracks and Forecasting
As we will see in the examples given, the Atlantic hurricanes travel west or northwest across the Atlantic and then recurve to the north and then northeast. This curvature is dictated by the Coriolis effect, which is caused by the Earth’s rotation. This pattern also occurs in the northern Pacific. Although these are predictable patterns, each storm has a unique path and there is great variation depending upon the atmospheric conditions near the storm, which act as steering forces.
Nevertheless, the patterns made by the historic tracks seen in the animation below show how the storms generally follow certain rules. This predictability aids in forecasting the paths using satellite data and numerical modeling.
Video: Hurricane Tracks Animation and Cumulative Map (0:14) (Video is not narrated.)
The cyclone’s interaction with the ocean’s surface has the effect of reducing the surface temperatures of the ocean. Once the storm approaches land, it encounters shallower water and begins interacting with coastal features. Friction and loss of the warm water “fuel” remove energy from the system, and it will dissipate once over land. It is at the ocean-land interface that the storm surge, which builds with the storm in the ocean, creates a tremendous hazard for those living on the coast.
Predicting the path and intensification of hurricanes can be very difficult. As we have learned earlier, there are many factors that control how a hurricane moves, and determining whether and by how much it will intensify is also complex. These variables include sea surface temperature, steering winds, atmospheric pressure, and several others. Because of this complexity, forecasting is now always done with atmospheric models that have become far more capable and accurate in recent years. There are dozens of models that are used in forecasting, and they don’t always agree. That is why hurricane forecasts have a cone of uncertainty. Moreover, different factors impact the storm path and whether it intensifies. The National Hurricane Center in the US compiles these model forecasts, and collectively they are called Spaghetti Diagrams because of the long, closely parallel paths of the different models. The models are used to build a cone of uncertainty that shows the range of the possible storm forecasts.
You are strongly encouraged to visit Hurricanes: Science and Society for an explanation of the processes that steer hurricanes. Then, use the information on this site to answer the following questions. These will help you master the lab activity.
- Why do disturbances move westward across the tropical Atlantic?
- What is the role of wind shear in the evolution of a hurricane?
- Do high-pressure systems such as the Bermuda high attract storms towards them or steer storms away from them?
- What is the name of the critical high-pressure system in the Atlantic that guides hurricane paths?
- Why do hurricanes gradually drift northward?
- What is the overall impact of wind shear on a storm?
- What is the impact of cooling water temperatures on the strength of a storm?
So in summary, hurricanes' paths are steered by winds which are a function of atmospheric pressure systems. Intensification is impacted by wind shear as well as ocean temperature. Satellite images of a hurricane help determine whether the storm is intensifying or weakening.