Creating Hurricanes with the flip of a switch

The powerful storm surge created by hurricanes often causes destruction. In an effort to improve intensity forecasting, ocean sciences professor, Brian Haus, of the University of Miami Rosenstiel school of marine and atmospheric science is studying the complex interactions between the air and the surface of the sea in extreme conditions.

TRANSCRIPT

The powerful storm surge created by hurricanes often causes destruction.

In an effort to improve intensity forecasting, ocean science professor Brian Haus of the University of Miami Rosenstiel School of Marine and Atmospheric Science is studying the complex interactions between the air and the surface of the sea in extreme conditions.

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At the surface in a Category 5 hurricane, there's so much bubbles in the water, and the spray that's in the air is so overwhelming and coming at such high velocities that it's just even difficult to tell where the surface is.

♪♪ And we can turn this on with the flip of a switch and a large diesel generator.

♪♪ As a Miamian, as somebody who lives here in this hurricane-prone place at the tip of a peninsula, there's a real visceral desire to get better forecasts, to get the information we need to keep all of us safe here in hurricane season.

I'm Brian Haus.

I study air-sea interaction and ocean waves in extreme hurricane conditions.

We're in the SUSTAIN Laboratory on the University of Miami's Rosenstiel School of Marine and Atmospheric Sciences.

The mission of the SUSTAIN Lab is to save lives by improving hurricane forecasting, particularly the intensity forecasting.

This is a unique facility in the world for doing wind-wave studies.

With a little bit of time, couple minutes, and some diesel fuel, we can generate a real wind speed of well over 200 miles an hour, the conditions equivalent to the most intense hurricanes that have ever been observed.

We can create a hurricane when we want it.

We can make it in the range of intensities we need to understand processes, and we can isolate key processes.

You can't isolate processes enough in the field to really understand the breaking waves, the dynamics, the spray, all of the stuff that happens in the real ocean.

The hurricanes get their heat from the ocean, the energy that powers them.

What's creating the spin of the storm, powering the storm, is the heat coming off the ocean, and that ocean surface has friction that it exerts on the storm.

So that's like pushing your hand across a glass tabletop versus pushing it across a rug versus pushing it across sandpaper.

That quantification of how hard it is to push, that's the drag coefficient.

To show the uncertainty, we're showing 1 mile of...

All of the forecast models are using a drag coefficient, and it used to be thought that it just increased with wind speed linearly, just kept going up.

But what we showed was that the drag coefficient, in fact, started to level off.

It didn't keep going up.

Now, the problem with that was what we had knew about the drag coefficient, that it wouldn't be possible to get a Category 5 storm.

What gives here?

Why is it that we know there's Category 5 storms, but the maximum potential intensity, based on what we know about the drag coefficient, wouldn't allow that?

That drag depends on the waves, the spray, all these sorts of things, and in ways that we don't fully understand.

So now we need to understand, 'Okay, how important is sea spray to this whole transfer process?'

And then that allows for the storm to go from a Category 3 to a Category 5 rapidly.

♪♪ When you're looking at the waves, your eye is drawn to the big huge waveforms.

And, really, a lot of the friction, a lot of the spray, a lot of stuff that's happening happens at centimeter scales.

Breaking down what happens at those small scales is critical for understanding how you integrate that over the whole ocean surface.

In the SUSTAIN Lab, we are using a lot of optical techniques to capture the quantity of spray.

We have what's called ultrasonic anemometers.

To measure the real fine-scale structure of the waves, we're using a technique called polarimetry, which is an optical technique.

That allows us to measure for every frame of the camera, for every pixel, what the local slope is, which is really powerful because optical techniques are great, but if you can imagine taking a picture of the ocean from a plane or something like that, you can't tell how big those waves are from that optical image.

Using this technique, we can actually get information on the shape of the surface and quantify what's going on.

If we are able to publish some, you know, good results on what the drag coefficient is up to a Category 5 hurricane, which we're going to be working on, people will start running tests with that new formulation immediately.

There's some things in science that we do that may take a decade to get through into what you're doing.

This is not one of them.

If you can show that with this new formulations that you get a better intensity forecast, that's going to be used by the next season.