Lab 1: Wind Shear and Hurricanes Teaching Tips

In this activity students model the winds that characterize hurricanes. Again, they explore what sorts of data a model can provide.

Modeling is a common scientific method. But in today’s research models are more likely to be virtual (computer algorithms) than physical. Whether the model can be viewed and manipulated physically, or is a representation, all models have limitations. Natural systems are complex, with many parameters. A model can only consider a few of those factors, ignoring the rest. Whenever students work with models, they should be encouraged to think about what they’ve considered and what their model ignores.

To make the model of hurricane winds, first think of the most sturdy place to set your fan. If you have heavy lab tables, you may be able to put them close enough to prop the fan between them. That raises the model so it’s visible to the class; but it’s likely you' will have to reach to send a horizontal “wind shear” across the top of the strips. You can also make a platform 5-10 inches from the floor.

It’s important to place the Mylar™ strips carefully. While some trial and error is inevitable, try placing them about 10 cm apart, about 10 cm in from the edge of a standard box fan. If they are too close, they will quickly tangle. If they are too far apart, the pattern may be difficult to observe.

The most obvious limitation of the model is that our storm stays in one place. In a real storm physical forces from Earth’s rotation (the Coriolis effect) cause storms in the Atlantic to trend west and northward. We’ll do more with that concept later.

Safety Note: Make sure that your fan has a safety grid on both sides, and remind students never to put fingers or objects through that grid. If you must run cords across your floor in order to reach power, cover the cords with duct tape or other secure covering. Keep electricity and water far apart.

Activity Images and Additional Tips

Mylar streamers should be cut to about 3 feet long and no wider than 2 inches.  Attach 3-5 steamers at a location equidistant from the center of the fan to the edge of the blade.  The fan should be sitting up on blocks high enough so that air flow from below is not disrupted.

 

With the fan turned on, the mylar streamers should be standing straight up, to model the convection current of a hurricane.

 

An optimal illustration of wind shear can be achieved by positioning one hair dryers as follows.  Hold one hair dryer at the at the edge of the fan and point it at the top of the streamers.  Hold the second hair dryer at the edge of the fan exactly opposite (180 degrees) from the first and point it at the bottom of the streamers.  The picture illustrates how the streamers are pushed one way at the top and the other way at the bottom, thus illustrating how shear can tear a storm apart.